Microsoft SQL Server Interview Question Part-1

1. What is RDBMS?

Relational Data Base Management Systems (RDBMS) are database management systems that maintain data records and indices in tables. Relationships may be created and maintained across and among the data and tables. In a relational database, relationships between data items are expressed by means of tables. Interdependencies among these tables are expressed by data values rather than by pointers. This allows a high degree of data independence. An RDBMS has the capability to recombine the data items from different files, providing powerful tools for data usage.

2. What are the properties of the Relational tables?

Relational tables have six properties:

1. Values are atomic.
2. Column values are of the same kind.
3. Each row is unique.
4. The sequence of columns is insignificant.
5. The sequence of rows is insignificant.
6. Each column must have a unique name.

3. What is Normalization?

Database normalization is a data design and organization process applied to data structures based on rules that help building relational databases. In relational database design, the process of organizing data to minimize redundancy is called normalization. Normalization usually involves dividing a database into two or more tables and defining relationships between the tables. The objective is to isolate data so that additions, deletions, and modifications of a field can be made in just one table and then propagated through the rest of the database via the defined relationships.

4. What is De-normalization?

De-normalization is the process of attempting to optimize the performance of a database by adding redundant data. It is sometimes necessary because current DBMSs implement the relational model poorly. A true relational DBMS would allow for a fully normalized database at the logical level, while providing physical storage of data that is tuned for high performance. De-normalization is a technique to move from higher to lower normal forms of database modeling in order to speed up database access.

5. What are different normalization forms?

1. 1NF: Eliminate Repeating Groups Make a separate table for each set of related attributes, and give each table a primary key. Each field contains at most one value from its attribute domain.

2. 2NF: Eliminate Redundant Data If an attribute depends on only part of a multi-valued key, remove it to a separate table.

3. 3NF: Eliminate Columns Not Dependent On Key If attributes do not contribute to a description of the key, remove them to a separate table. All attributes must be directly dependent on the primary key.

4. BCNF: Boyce-Codd Normal Form If there are non-trivial dependencies between candidate key attributes, separate them out into distinct tables.

5. 4NF: Isolate Independent Multiple Relationships No table may contain two or more 1:n or n:m relationships that are not directly related.

6. 5NF: Isolate Semantically Related Multiple Relationships There may be practical constrains on information that justify separating logically related many-to- many relationships.

7. ONF: Optimal Normal Form A model limited to only simple (elemental) facts, as expressed in Object Role Model notation.

8. DKNF: Domain-Key Normal Form A model free from all modification anomalies is said to be in DKNF.

Remember, these normalization guidelines are cumulative. For a database to be in 3NF, it must first fulfill all the criteria of a 2NF and 1NF database.

6. What is Stored Procedure?

A stored procedure is a named group of SQL statements that have been previously created and stored in the server database. Stored procedures accept input parameters so that a single procedure can be used over the network by several clients using different input data. And when the procedure is modified, all clients automatically get the new version. Stored procedures reduce network traffic and improve performance. Stored procedures can be used to help ensure the integrity of the database.

e.g. sp_helpdb, sp_renamedb, sp_depends etc.

7. What is Trigger?

A trigger is a SQL procedure that initiates an action when an event (INSERT, DELETE or UPDATE) occurs. Triggers are stored in and managed by the DBMS. Triggers are used to maintain the referential integrity of data by changing the data in a systematic fashion. A trigger cannot be called or executed; DBMS automatically fires the trigger as a result of a data modification to the associated table. Triggers can be viewed as similar to stored procedures in that both consist of procedural logic that is stored at the database level. Stored procedures, however, are not event-drive and are not attached to a specific table as triggers are. Stored procedures are explicitly executed by invoking a CALL to the procedure while triggers are implicitly executed. In addition, triggers can also execute stored procedures.

8. What is Nested Trigger?

A trigger can also contain INSERT, UPDATE and DELETE logic within itself, so when the trigger is fired because of data modification it can also cause another data modification, thereby firing another trigger. A trigger that contains data modification logic within itself is called a nested trigger.

9. What is View?

A simple view can be thought of as a subset of a table. It can be used for retrieving data, as well as updating or deleting rows. Rows updated or deleted in the view are updated or deleted in the table the view was created with. It should also be noted that as data in the original table changes, so does data in the view, as views are the way to look at part of the original table. The results of using a view are not permanently stored in the database. The data accessed through a view is actually constructed using standard T-SQL select command and can come from one to many different base tables or even other views.

10. What is Index?

An index is a physical structure containing pointers to the data. Indices are created in an existing table to locate rows more quickly and efficiently. It is possible to create an index on one or more columns of a table, and each index is given a name. The users cannot see the indexes; they are just used to speed up queries. Effective indexes are one of the best ways to improve performance in a database application. A table scan happens when there is no index available to help a query. In table scan SQL Server examines every row in the table to satisfy the query results. Table scans are sometimes unavoidable, but on large tables, scans have a terrific impact on performance.

11. What is a Linked Server?

Linked Servers is a concept in SQL Server by which we can add other SQL Server to a Group and query both the SQL Server dbs using T-SQL Statements. With a linked server, you can create very clean, easy to follow, SQL statements that allow remote data to be retrieved, joined and combined with local data. Stored Procedure sp_addlinkedserver, sp_addlinkedsrvlogin will be used add new Linked Server.

12. What is Cursor?

Cursor is a database object used by applications to manipulate data in a set on a row-by- row basis, instead of the typical SQL commands that operate on all the rows in the set at one time.

In order to work with a cursor we need to perform some steps in the following order:

1. Declare cursor

2. Open cursor

3. Fetch row from the cursor

4. Process fetched row

5. Close cursor

6. Deallocate cursor

13. What is Collation?

Collation refers to a set of rules that determine how data is sorted and compared. Character data is sorted using rules that define the correct character sequence, with options for specifying case sensitivity, accent marks, kana character types and character width.

14. What is Difference between Function and Stored Procedure?

UDF can be used in the SQL statements anywhere in the WHERE/HAVING/SELECT section where as Stored procedures cannot be. UDFs that return tables can be treated as another rowset. This can be used in JOINs with other tables. Inline UDF's can be thought of as views that take parameters and can be used in JOINs and other Rowset operations.

15. What is sub-query? Explain properties of sub-query?

Sub-queries are often referred to as sub-selects, as they allow a SELECT statement to be executed arbitrarily within the body of another SQL statement. A sub-query is executed by enclosing it in a set of parentheses. Sub-queries are generally used to return a single row as an atomic value, though they may be used to compare values against multiple rows with the IN keyword. A subquery is a SELECT statement that is nested within another T-SQL statement.

A subquery SELECT statement if executed independently of the T-SQL statement, in which it is nested, will return a resultset. Meaning a subquery SELECT statement can standalone and is not depended on the statement in which it is nested.

A subquery SELECT statement can return any number of values, and can be found in, the column list of a SELECT statement, a FROM, GROUP BY, HAVING, and/or ORDER BY clauses of a T-SQL statement. A Subquery can also be used as a parameter to a function call. Basically a subquery can be used anywhere an expression can be used.

16. What are different Types of Join?

1. Cross Join A cross join that does not have a WHERE clause produces the Cartesian product of the tables involved in the join. The size of a Cartesian product result set is the number of rows in the first table multiplied by the number of rows in the second table. The common example is when company wants to combine each product with a pricing table to analyze each product at each price.

2. Inner Join A join that displays only the rows that have a match in both joined tables is known as inner Join. This is the default type of join in the Query and View Designer.

3. Outer Join A join that includes rows even if they do not have related rows in the joined table is an Outer Join. You can create three different outer join to specify the unmatched rows to be included:

 Left Outer Join: In Left Outer Join all rows in the first-named table i.e. "left" table, which appears leftmost in the JOIN clause are included. Unmatched rows in the right table do not appear.

 Right Outer Join: In Right Outer Join all rows in the second-named table i.e. "right" table, which appears rightmost in the JOIN clause are included. Unmatched rows in the left table are not included.

 Full Outer Join: In Full Outer Join all rows in all joined tables are included, whether they are matched or not.

4. Self Join This is a particular case when one table joins to itself, with one or two aliases to avoid confusion. A self join can be of any type, as long as the joined tables are the same. A self join is rather unique in that it involves a relationship with only one table. The common example is when company has a hierarchal reporting structure whereby one member of staff reports to another. Self Join can be Outer Join or Inner Join.

17. What are primary keys and foreign keys?

Primary keys are the unique identifiers for each row. They must contain unique values and cannot be null. Due to their importance in relational databases, Primary keys are the most fundamental of all keys and constraints. A table can have only one Primary key. Foreign keys are both a method of ensuring data integrity and a manifestation of the relationship between tables.

18. What is User Defined Functions? What kind of User-Defined Functions can be created?

User-Defined Functions allow defining its own T-SQL functions that can accept 0 or more parameters and return a single scalar data value or a table data type.

 Different Kinds of User-Defined Functions created are:

1. Scalar User-Defined Function A Scalar user-defined function returns one of the scalar data types. Text, ntext, image and timestamp data types are not supported. These are the type of user-defined functions that most developers are used to in other programming languages. You pass in 0 to many parameters and you get a return value.

2. Inline Table-Value User-Defined Function An Inline Table-Value user-defined function returns a table data type and is an exceptional alternative to a view as the user-defined function can pass parameters into a T-SQL select command and in essence provide us with a parameterized, non-updateable view of the underlying tables.

3. Multi-statement Table-Value User-Defined Function A Multi-Statement Table-Value user- defined function returns a table and is also an exceptional alternative to a view as the function can support multiple T-SQL statements to build the final result where the view is limited to a single SELECT statement. Also, the ability to pass parameters into a TSQL select command or a group of them gives us the capability to in essence create a parameterized, non-updateable view of the data in the underlying tables. Within the create function command you must define the table structure that is being returned. After creating this type of user-defined function, It can be used in the FROM clause of a T-SQL command unlike the behavior found when using a stored procedure which can also return record sets.

19. What is Identity?

Identity (or AutoNumber) is a column that automatically generates numeric values. A start and increment value can be set, but most DBA leave these at 1. A GUID column also generates numbers; the value of this cannot be controlled. Identity/GUID columns do not need to be indexed.

20. What is Data Warehousing?

1. Subject-oriented, meaning that the data in the database is organized so that all the data elements relating to the same real-world event or object are linked together;

2. Time-variant, meaning that the changes to the data in the database are tracked and recorded so that reports can be produced showing changes over time;

3. Non-volatile, meaning that data in the database is never over-written or deleted, once committed, the data is static, read-only, but retained for future reporting.

4. Integrated, meaning that the database contains data from most or all of an organization's operational applications, and that this data is made consistent

21. Which TCP/IP port does SQL Server run on? How can it be changed?

SQL Server runs on port 1433. It can be changed from the Network Utility TCP/IP properties.

22. What are the difference between clustered and a non-clustered index?

1. A clustered index is a special type of index that reorders the way records in the table are physically stored. Therefore table can have only one clustered index. The leaf nodes of a clustered index contain the data pages.

2. A non clustered index is a special type of index in which the logical order of the index does not match the physical stored order of the rows on disk. The leaf node of a non clustered index does not consist of the data pages. Instead, the leaf nodes contain index rows.

23. What are the different index configurations a table can have?

A table can have one of the following index configurations:

1. No indexes

2. A clustered index

3. A clustered index and many nonclustered indexes

4. A nonclustered index

5. Many nonclustered indexes

24. What are different types of Collation Sensitivity?

1. Case sensitivity - A and a, B and b, etc.

2. Accent sensitivity

3. Kana Sensitivity - When Japanese kana characters Hiragana and Katakana are treated differently, it is called Kana sensitive.

4. Width sensitivity - A single-byte character (half-width) and the same character represented as a double-byte character (full-width) are treated differently than it is width sensitive.

25. What is OLTP (Online Transaction Processing)?

In OLTP - online transaction processing systems relational database design use the discipline of data modeling and generally follow the Codd rules of data normalization in order to ensure absolute data integrity. Using these rules complex information is broken down into its most simple structures (a table) where all of the individual atomic level elements relate to each other and satisfy the normalization rules.

26. What's the difference between a primary key and a unique key?

Both primary key and unique key enforces uniqueness of the column on which they are defined. But by default primary key creates a clustered index on the column, where are unique creates a nonclustered index by default. Another major difference is that, primary key doesn't allow NULLs, but unique key allows one NULL only.

27. What is difference between DELETE and TRUNCATE commands?

Delete command removes the rows from a table based on the condition that we provide with a WHERE clause. Truncate will actually remove all the rows from a table and there will be no data in the table after we run the truncate command.

1. TRUNCATE:

1. TRUNCATE is faster and uses fewer system and transaction log resources than DELETE.

2. TRUNCATE removes the data by deallocating the data pages used to store the table's data, and only the page deallocations are recorded in the transaction log.


3. TRUNCATE removes all rows from a table, but the table structure, its columns, constraints, indexes and so on, remains. The counter used by an identity for new rows is reset to the seed for the column.

4. You cannot use TRUNCATE TABLE on a table referenced by a FOREIGN KEY constraint. Because TRUNCATE TABLE is not logged, it cannot activate a trigger.

5. TRUNCATE cannot be rolled back.

6. TRUNCATE is DDL Command.

7. TRUNCATE Resets identity of the table

2. DELETE:

1. DELETE removes rows one at a time and records an entry in the transaction log for each deleted row.

2. If you want to retain the identity counter, use DELETE instead. If you want to remove table definition and its data, use the DROP TABLE statement.

3. DELETE Can be used with or without a WHERE clause

4. DELETE Activates Triggers.

5. DELETE can be rolled back.

6. DELETE is DML Command.

7. DELETE does not reset identity of the table.

Note: DELETE and TRUNCATE both can be rolled back when surrounded by TRANSACTION if the current session is not closed. If TRUNCATE is written in Query Editor surrounded by TRANSACTION and if session is closed, it can not be rolled back but DELETE can be rolled back.

28. When is the use of UPDATE_STATISTICS command?

This command is basically used when a large processing of data has occurred. If a large amount of deletions any modification or Bulk Copy into the tables has occurred, it has to update the indexes to take these changes into account. UPDATE_STATISTICS updates the indexes on these tables accordingly.

29. What is the difference between a HAVING CLAUSE and a WHERE CLAUSE?

They specify a search condition for a group or an aggregate. But the difference is that HAVING can be used only with the SELECT statement. HAVING is typically used in a GROUP BY clause. When GROUP BY is not used, HAVING behaves like a WHERE clause. Having Clause is basically used only with the GROUP BY function in a query whereas WHERE Clause is applied to each row before they are part of the GROUP BY function in a query.


30. What are the properties and different Types of Sub-Queries?

1. Properties of Sub-Query

1. A sub-query must be enclosed in the parenthesis.

2. A sub-query must be put in the right hand of the comparison operator, and

3. A sub-query cannot contain an ORDER-BY clause.

4. A query can contain more than one sub-query.

2. Types of Sub-Query

1. Single-row sub-query, where the sub-query returns only one row.

2. Multiple-row sub-query, where the sub-query returns multiple rows,. and

3. Multiple column sub-query, where the sub-query returns multiple columns

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ADVANCE JAVA BASIC INTERVIEW QUESTION PART 4

151. What is the difference between the File and RandomAccessFile classes?

The File class encapsulates the files and directories of the local file system. The RandomAccessFile class provides the methods needed to directly access data contained in any part of a file.

152. What happens when you add a double value to a String?

The result is a String object.

153. What is your platform's default character encoding?

If you are running Java on English Windows platforms, it is probably Cp1252. If you are running Java on English Solaris platforms, it is most likely 8859_1.

154. Which package is always imported by default?

The java.lang package is always imported by default.

155. What interface must an object implement before it can be written to a stream as an object?

An object must implement the Serializable or Externalizable interface before it can be written to a stream as an object.

156. How are this and super used?

this is used to refer to the current object instance. super is used to refer to the variables and methods of the superclass of the current object instance

157. What is a compilation unit?

A compilation unit is a Java source code file.

158. What interface is extended by AWT event listeners?

All AWT event listeners extend the java.util.EventListener interface.

159. What restrictions are placed on method overriding?

Overridden methods must have the same name, argument list, and return type. The overriding method may not limit the access of the method it overrides. The overriding method may not throw any exceptions that may not be thrown by the overridden method.

160. How can a dead thread be restarted?

A dead thread cannot be restarted.

161. What happens if an exception is not caught?

An uncaught exception results in the uncaughtException() method of the thread's ThreadGroup being invoked, which eventually results in the termination of the program in which it is thrown.

162. What is a layout manager?

A layout manager is an object that is used to organize components in a container

163. Which arithmetic operations can result in the throwing of an ArithmeticException?

Integer / and % can result in the throwing of an ArithmeticException.

164. What are three ways in which a thread can enter the waiting state?

A thread can enter the waiting state by invoking its sleep() method, by blocking on I/O, by unsuccessfully attempting to acquire an object's lock, or by invoking an object's wait() method. It can also enter the waiting state by invoking its (deprecated) suspend() method.

165. Can an abstract class be final?

An abstract class may not be declared as final.

166. What is the ResourceBundle class?

The ResourceBundle class is used to store locale-specific resources that can be loaded by a program to tailor the program's appearance to the particular locale in which it is being run.

167. What happens if a try-catch- finally statement does not have a catch clause to handle an exception that is thrown within the body of the try statement?

The exception propagates up to the next higher level try-catch statement (if any) or results in the program's termination.

168. What is numeric promotion?

Numeric promotion is the conversion of a smaller numeric type to a larger numeric type, so that integer and floating-point operations may take place. In numerical promotion, byte, char, and short values are converted to int values. The int values are also converted to long values, if necessary. The long and float values are converted to double values, as required

169. What is the difference between a Scrollbar and a ScrollPane?

A Scrollbar is a Component, but not a Container. A ScrollPane is a Container. A ScrollPane handles its own events and performs its own scrolling.

170. What is the difference between a public and a non-public class?

A public class may be accessed outside of its package. A non-public class may not be accessed outside of its package.

171. To what value is a variable of the boolean type automatically initialized?

The default value of the boolean type is false.

172. Can try statements be nested?

Try statements may be tested.

173. What is the difference between the prefix and postfix forms of the ++ operator?

The prefix form performs the increment operation and returns the value of the increment operation. The postfix form returns the current value all of the expression and then performs the increment operation on that value.

174. What is the purpose of a statement block?

A statement block is used to organize a sequence of statements as a single statement group

175. What is a Java package and how is it used?

A Java package is a naming context for classes and interfaces. A package is used to create a separate name space for groups of classes and interfaces. Packages are also used to organize related classes and interfaces into a single API unit and to control accessibility to these classes and interfaces.

176. What modifiers may be used with a top-level class?

A top-level class may be public, abstract, or final.

177. What are the Object and Class classes used for?

The Object class is the highest-level class in the Java class hierarchy. The Class class is used to represent the classes and interfaces that are loaded by a Java program..

178. How does a try statement determine which catch clause should be used to handle an exception?

When an exception is thrown within the body of a try statement, the catch clauses of the try statement are examined in the order in which they appear. The first catch clause that is capable of handling the exception is executed. The remaining catch clauses are ignored.

179. Can an unreachable object become reachable again?

An unreachable object may become reachable again. This can happen when the object's finalize() method is invoked and the object performs an operation which causes it to become accessible to reachable objects.

180. When is an object subject to garbage collection?

An object is subject to garbage collection when it becomes unreachable to the program in which it is used

181. What method must be implemented by all threads?

All tasks must implement the run() method, whether they are a subclass of Thread or implement the Runnable interface.

182. What methods are used to get and set the text label displayed by a Button object?

getLabel() and setLabel().

183. Which Component subclass is used for drawing and painting?

Canvas

184. What are synchronized methods and synchronized statements?

Synchronized methods are methods that are used to control access to an object. A thread only executes a synchronized method after it has acquired the lock for the method's object or class. Synchronized statements are similar to synchronized methods. A synchronized statement can only be executed after a thread has acquired the lock for the object or class referenced in the synchronized statement.

185. What are the two basic ways in which classes that can be run as threads may be defined?

A thread class may be declared as a subclass of Thread, or it may implement the Runnable interface.

186. What are the problems faced by Java programmers who don't use layout managers?

Without layout managers, Java programmers are faced with determining how their GUI will be displayed across multiple windowing systems and finding a common sizing and positioning that will work within the constraints imposed by each windowing system

ADVANCE JAVA BASIC INTERVIEW QUESTION PART 3

101. Is "abc" a primitive value?

The String literal "abc" is not a primitive value. It is a String object.

102. What is the relationship between an event-listener interface and an event-adapter class?

An event-listener interface defines the methods that must be implemented by an event handler for a particular kind of event. An event adapter provides a default implementation of an event-listener interface

103. What restrictions are placed on the values of each case of a switch statement?

During compilation, the values of each case of a switch statement must evaluate to a value that can be promoted to an int value.

104. What modifiers may be used with an interface declaration?

An interface may be declared as public or abstract.

105. Is a class a subclass of itself?

A class is a subclass of itself.

106. What is the highest-level event class of the event-delegation model?

The java.util.EventObject class is the highest-level class in the event-delegation class hierarchy.

107. What event results from the clicking of a button?

The ActionEvent event is generated as the result of the clicking of a button.

108. How can a GUI component handle its own events?

A component can handle its own events by implementing the required event-listener interface and adding itself as its own event listener.

109. How are the elements of a GridBagLayout organized?

The elements of a GridBagLayout are organized according to a grid. However, the elements are of different sizes and may occupy more than one row or column of the grid. In addition, the rows and columns may have different sizes.

110. What advantage do Java's layout managers provide over traditional windowing systems?

Java uses layout managers to lay out components in a consistent manner across all windowing platforms. Since Java's layout managers aren't tied to absolute sizing and positioning, they are able to accomodate platform-specific differences among windowing systems.

111. What is the Collection interface?

The Collection interface provides support for the implementation of a mathematical bag - an unordered collection of objects that may contain duplicates.

112. What modifiers can be used with a local inner class?

A local inner class may be final or abstract.

113. What is the difference between static and non-static variables?

A static variable is associated with the class as a whole rather than with specific instances of a class. Non-static variables take on unique values with each object instance.

114. What is the difference between the paint() and repaint() methods?

The paint() method supports painting via a Graphics object. The repaint() method is used to cause paint() to be invoked by the AWT painting thread.

115. What is the purpose of the File class?

The File class is used to create objects that provide access to the files and directories of a local file system.

116. Can an exception be rethrown?

Yes, an exception can be rethrown.

117. Which Math method is used to calculate the absolute value of a number?

The abs() method is used to calculate absolute values.

118. How does multithreading take place on a computer with a single CPU?

The operating system's task scheduler allocates execution time to multiple tasks. By quickly switching between executing tasks, it creates the impression that tasks execute sequentially.

119. When does the compiler supply a default constructor for a class?

The compiler supplies a default constructor for a class if no other constructors are provided.

120. When is the finally clause of a try-catch- finally statement executed?

The finally clause of the try-catch- finally statement is always executed unless the thread of execution terminates or an exception occurs within the execution of the finally clause.

121. Which class is the immediate superclass of the Container class?

Component

122. If a method is declared as protected, where may the method be accessed?

A protected method may only be accessed by classes or interfaces of the same package or by subclasses of the class in which it is declared.

123. How can the Checkbox class be used to create a radio button?

By associating Checkbox objects with a CheckboxGroup.

124. Which non-Unicode letter characters may be used as the first character of an identifier?

The non-Unicode letter characters $ and _ may appear as the first character of an identifier

125. What restrictions are placed on method overloading?

Two methods may not have the same name and argument list but different return types.

126. What happens when you invoke a thread's interrupt method while it is sleeping or waiting?

When a task's interrupt() method is executed, the task enters the ready state. The next time the task enters the running state, an InterruptedException is thrown

127. What is casting?

There are two types of casting, casting between primitive numeric types and casting between object references. Casting between numeric types is used to convert larger values, such as double values, to smaller values, such as byte values. Casting between object references is used to refer to an object by a compatible class, interface, or array type reference.

128. What is the return type of a program's main() method?

A program's main() method has a void return type.

129. Name four Container classes.

Window, Frame, Dialog, FileDialog, Panel, Applet, or ScrollPane

130. What is the difference between a Choice and a List?

A Choice is displayed in a compact form that requires you to pull it down to see the list of available choices. Only one item may be selected from a Choice. A List may be displayed in such a way that several List items are visible. A List supports the selection of one or more List items.

131. What class of exceptions are generated by the Java run-time system?

The Java runtime system generates RuntimeException and Error exceptions.

132. What class allows you to read objects directly from a stream?

The ObjectInputStream class supports the reading of objects from input streams

133. What is the difference between a field variable and a local variable?

A field variable is a variable that is declared as a member of a class. A local variable is a variable that is declared local to a method.

134. Under what conditions is an object's finalize() method invoked by the garbage collector?

The garbage collector invokes an object's finalize() method when it detects that the object has become unreachable.

135. What is the relationship between a method's throws clause and the exceptions that can be thrown during the method's execution?

A method's throws clause must declare any checked exceptions that are not caught within the body of the method.

136. What is the difference between the JDK 1.02 event model and the event-delegation model introduced with JDK 1.1?

The JDK 1.02 event model uses an event inheritance or bubbling approach. In this model, components are required to handle their own events. If they do not handle a particular event, the event is inherited by (or bubbled up to) the component's container. The container then either handles the event or it is bubbled up to its container and so on, until the highest-level container has been tried.

In the event-delegation model, specific objects are designated as event handlers for GUI components. These objects implement event-listener interfaces. The event-delegation model is more efficient than the event-inheritance model because it eliminates the processing required to support the bubbling of unhandled events.

137. How is it possible for two String objects with identical values not to be equal under the == operator?

The == operator compares two objects to determine if they are the same object in memory. It is possible for two String objects to have the same value, but located indifferent areas of memory.

138. Why are the methods of the Math class static?

So they can be invoked as if they are a mathematical code library

139. What Checkbox method allows you to tell if a Checkbox is checked?

getState().

140. What state is a thread in when it is executing?

An executing thread is in the running state.

141. What are the legal operands of the instanceof operator?

The left operand is an object reference or null value and the right operand is a class, interface, or array type.

142. How are the elements of a GridBagLayout organized?

The elements of a GridBagLayout are of equal size and are laid out using the squares of a grid.

143. What an I/O filter?

An I/O filter is an object that reads from one stream and writes to another, usually altering the data in some way as it is passed from one stream to another.

144. If an object is garbage collected, can it become reachable again?

Once an object is garbage collected, it ceases to exist. It can no longer become reachable again

145. What is the Set interface?

The Set interface provides methods for accessing the elements of a finite mathematical set. Sets do not allow duplicate elements.

146. What classes of exceptions may be thrown by a throw statement?

A throw statement may throw any expression that may be assigned to the Throwable type.

147. What are E and PI?

E is the base of the natural logarithm and PI is mathematical value pi.

148. Are true and false keywords?

The values true and false are not keywords.

149. What is a void return type?

A void return type indicates that a method does not return a value.

150. What is the purpose of the enableEvents() method?

The enableEvents() method is used to enable an event for a particular object. Normally, an event is enabled when a listener is added to an object for a particular event. The enableEvents() method is used by objects that handle events by overriding their event-dispatch methods.

ADVANCE JAVA BASIC INTERVIEW QUESTION PART 2

51. Name three subclasses of the Component class.

Box.Filler, Button, Canvas, Checkbox, Choice, Container, Label, List, Scrollbar, or TextComponent.

51. Name three subclasses of the Component class.

Box.Filler, Button, Canvas, Checkbox, Choice, Container, Label, List, Scrollbar, or TextComponent.

52. What is the GregorianCalendar class?

The GregorianCalendar class provides support for traditional Western calendars.

53. Which Container method is used to cause a container to be laid out and redisplayed?

validate() method is used to cause a container to be laid out and redisplayed.

54. What is the purpose of the Runtime class?

The purpose of the Runtime class is to provide access to the Java runtime system.

55. How many times may an object's finalize() method be invoked by the garbage collector?

An object's finalize() method may only be invoked once by the garbage collector.

56. What is the purpose of the finally clause of a try-catch- finally statement?

The finally clause is used to provide the capability to execute code no matter whether or not an exception is thrown or caught.

57. What is the argument type of a program's main() method?

A program's main() method takes an argument of the String[] type.

58. Which Java operator is right associative?

The = operator is right associative.

59. Can a double value be cast to a byte?

Yes, a double value can be cast to a byte.

60. What must a class do to implement an interface?

It must provide all of the methods in the interface and identify the interface in its implements clause

61. What method is invoked to cause an object to begin executing as a separate thread?

The start() method of the Thread class is invoked to cause an object to begin executing as a separate thread.

62. Name two subclasses of the TextComponent class.

TextField and TextArea

63. Which containers may have a MenuBar?

Frame.

64. How are commas used in the intialization and iteration parts of a for statement?

Commas are used to separate multiple statements within the initialization and iteration parts of a for statement.

65. What is the purpose of the wait(), notify(), and notifyAll() methods?

The wait(), notify(), and notifyAll() methods are used to provide an efficient way for threads to wait for a shared resource. When a thread executes an object's wait() method, it enters the waiting state. It only enters the ready state after another thread invokes the object's notify() or notifyAll() methods..

66. What is an abstract method?

An abstract method is a method whose implementation is deferred to a subclass

67. How are Java source code files named?

A Java source code file takes the name of a public class or interface that is defined within the file. A source code file may contain at most one public class or interface. If a public class or interface is defined within a source code file, then the source code file must take the name of the public class or interface. If no public class or interface is defined within a source code file, then the file must take on a name that is different than its classes and interfaces. Source code files use the .java extension.

68. What is the relationship between the Canvas class and the Graphics class?

A Canvas object provides access to a Graphics object via its paint() method.

69. What are the high-level thread states?

The high-level thread states are ready, running, waiting, and dead.

70. What value does read() return when it has reached the end of a file?

The read() method returns -1 when it has reached the end of a file.

71. Can a Byte object be cast to a double value?

No. An object cannot be cast to a primitive value.

72. What is the difference between a static and a non-static inner class?

A non-static inner class may have object instances that are associated with instances of the class's outer class. A static inner class does not have any object instances.

73. What is the difference between the String and StringBuffer classes?

String objects are constants. StringBuffer objects are not constants.

74. If a variable is declared as private, where may the variable be accessed?

A private variable may only be accessed within the class in which it is declared.

75. What is an object's lock and which object's have locks?

An object's lock is a mechanism that is used by multiple threads to obtain synchronized access
to the object. A thread may execute a synchronized method of an object only after it has acquired the
object's lock. All objects and classes have locks. A class's lock is acquired on the
class's Class object.

76. What is the Dictionary class?

The Dictionary class provides the capability to store key-value pairs.

77. How are the elements of a BorderLayout organized?

The elements of a BorderLayout are organized at the borders (North, South, East, and West) and the center of a container.

78. What is the % operator?

It is referred to as the modulo or remainder operator. It returns the remainder of dividing the first operand by the second operand.

79. When can an object reference be cast to an interface reference?

An object reference be cast to an interface reference when the object implements the referenced interface.

80. What is the difference between a Window and a Frame?

The Frame class extends Window to define a main application window that can have a menu bar.

81. Which class is extended by all other classes?

The Object class is extended by all other classes.

82. Can an object be garbage collected while it is still reachable?

A reachable object cannot be garbage collected. Only unreachable objects may be garbage collected..

83. Is the ternary operator written x : y ? z or x ? y : z ?

It is written x ? y : z.

84. What is the difference between the Font and FontMetrics classes?

The FontMetrics class is used to define implementation-specific properties, such as ascent and descent, of a Font object.

85. How is rounding performed under integer division?

The fractional part of the result is truncated. This is known as rounding toward zero.

86. What happens when a thread cannot acquire a lock on an object?

If a thread attempts to execute a synchronized method or synchronized statement and is unable to acquire an object's lock, it enters the waiting state until the lock becomes available.

87. What is the difference between the Reader/Writer class hierarchy and the InputStream/OutputStream class hierarchy?

The Reader/Writer class hierarchy is character-oriented, and the InputStream/OutputStream class hierarchy is byte-oriented.

88. What classes of exceptions may be caught by a catch clause?

A catch clause can catch any exception that may be assigned to the Throwable type. This includes the Error and Exception types.

89. If a class is declared without any access modifiers, where may the class be accessed?

A class that is declared without any access modifiers is said to have package access. This means that the class can only be accessed by other classes and interfaces that are defined within the same package.

90. What is the SimpleTimeZone class?

The SimpleTimeZone class provides support for a Gregorian calendar

91. What is the Map interface?

The Map interface replaces the JDK 1.1 Dictionary class and is used associate keys with values.

92. Does a class inherit the constructors of its superclass?

A class does not inherit constructors from any of its superclasses.

93. For which statements does it make sense to use a label?

The only statements for which it makes sense to use a label are those statements that can enclose a break or continue statement.

94. What is the purpose of the System class?

The purpose of the System class is to provide access to system resources.

95. Which TextComponent method is used to set a TextComponent to the read-only state?

setEditable()

96. How are the elements of a CardLayout organized?

The elements of a CardLayout are stacked, one on top of the other, like a deck of cards

97. Is &&= a valid Java operator?

No. It is not a valid java operator.

98. Name the eight primitive Java types.

The eight primitive types are byte, char, short, int, long, float, double, and boolean.

99. Which class should you use to obtain design information about an object?

The Class class is used to obtain information about an object's design.

100. What is the relationship between clipping and repainting?

When a window is repainted by the AWT painting thread, it sets the clipping regions to the area of the window that requires repainting.

Advance Java Basic Interview Question Part 1

1. What is a transient variable?

A transient variable is a variable that may not be serialized.

2. Which containers use a border Layout as their default layout?

The Window, Frame and Dialog classes use a border layout as their default layout.

3. Why do threads block on I/O?

Threads block on I/O (that is enters the waiting state) so that other threads may execute while the I/O Operation is performed.

' 4. How are Observer and Observable used?

Objects that subclass the Observable class maintain a list of observers. When an Observable object is updated it invokes the update() method of each of its observers to notify the observers that it has changed state. The Observer interface is implemented by objects that observe Observable objects.

5. What is synchronization and why is it important?

With respect to multithreading, synchronization is the capability to control the access of multiple threads to shared resources. Without synchronization, it is possible for one thread to modify a shared object while another thread is in the process of using or updating that object's value. This often leads to significant errors.

6. Can a lock be acquired on a class?

Yes, a lock can be acquired on a class. This lock is acquired on the class's Class object

7. What's new with the stop(), suspend() and resume() methods in JDK 1.2?

The stop(), suspend() and resume() methods have been deprecated in JDK 1.2.

8. Is null a keyword?

The null is not a keyword.

9. What is the preferred size of a component?

The preferred size of a component is the minimum component size that will allow the component to display normally.

10. What method is used to specify a container's layout?

The setLayout() method is used to specify a container's layout.

11. Which containers use a FlowLayout as their default layout?

The Panel and Applet classes use the FlowLayout as their default layout.

12. What state does a thread enter when it terminates its processing?

When a thread terminates its processing, it enters the dead state

13. What is the Collections API?

The Collections API is a set of classes and interfaces that support operations on collections of objects.

14. Which characters may be used as the second character of an identifier, but not as the first character of an identifier?

The digits 0 through 9 may not be used as the first character of an identifier but they may be used after the first character of an identifier.

15. What is the List interface?

The List interface provides support for ordered collections of objects.

16. How does Java handle integer overflows and underflows?

It uses those low order bytes of the result that can fit into the size of the type allowed by the operation.

17. What is the Vector class?

The Vector class provides the capability to implement a growable array of objects

18. What modifiers may be used with an inner class that is a member of an outer class?

A (non-local) inner class may be declared as public, protected, private, static, final, or abstract

19. What is an Iterator interface?

The Iterator interface is used to step through the elements of a Collection.

20. What is the difference between the >> and >>> operators?

The >> operator carries the sign bit when shifting right. The >>> zero-fills bits that have been shifted out.

21. Which method of the Component class is used to set the position and size of a component?

setBounds() method is used to set the position and size of a component.

22. What is the difference between yielding and sleeping?

When a task invokes its yield() method, it returns to the ready state. When a task invokes its sleep() method, it returns to the waiting state.

23. Which java.util classes and interfaces support event handling?

The EventObject class and the EventListener interface support event processing.

24. Is sizeof a keyword?

The sizeof operator is not a keyword.

25. What are wrapped classes?

Wrapped classes are classes that allow primitive types to be accessed as objects.

26. Does garbage collection guarantee that a program will not run out of memory?

Garbage collection does not guarantee that a program will not run out of memory. It is possible for programs to use up memory resources faster than they are garbage collected. It is also possible for programs to create objects that are not subject to garbage collection.

27. What restrictions are placed on the location of a package statement within a source code file?

A package statement must appear as the first line in a source code file (excluding blank lines and comments).

28. Can an object's finalize() method be invoked while it is reachable?

An object's finalize() method cannot be invoked by the garbage collector while the object is still reachable. However, an object's finalize() method may be invoked by other objects.

29. What is the immediate superclass of the Applet class?

Panel

30. What is the difference between pre-emptive scheduling and time slicing?

Under pre-emptive scheduling, the highest priority task executes until it enters the waiting or dead states or a higher priority task comes into existence. Under time slicing, a task executes for a predefined slice of time and then re-enters the pool of ready tasks. The scheduler then determines which task should execute next, based on priority and other factors

31. Name three Component subclasses that support painting.

The Canvas, Frame, Panel, and Applet classes support painting.

32. What value does readLine() return when it has reached the end of a file?

The readLine() method returns null when it has reached the end of a file.

33. What is the immediate superclass of the Dialog class?

Window

34. What is clipping?

Clipping is the process of confining paint operations to a limited area or shape.

35. What is a native method?

A native method is a method that is implemented in a language other than Java.

36. Can a for statement loop indefinitely?

Yes, a for statement can loop indefinitely. For example, consider the following:

for(;;) ;

37. What are order of precedence and associativity, and how are they used?

Order of precedence determines the order in which operators are evaluated in expressions. Associativity determines whether an expression is evaluated left-to- right or right-to- left.

38. When a thread blocks on I/O, what state does it enter?

A thread enters the waiting state when it blocks on I/O.

39. To what value is a variable of the String type automatically initialized?

The default value of an String type is null.

40. What is the catch or declare rule for method declarations?

If a checked exception may be thrown within the body of a method, the method must either catch the exception or declare it in its throws clause.

41. What is the difference between a MenuItem and a CheckboxMenuItem?

The CheckboxMenuItem class extends the MenuItem class to support a menu item that may be checked or unchecked.

42. What is a task's priority and how is it used in scheduling?

A task's priority is an integer value that identifies the relative order in which it should be executed with respect to other tasks. The scheduler attempts to schedule higher priority tasks before lower priority tasks

43. What class is the top of the AWT event hierarchy?

The java.awt.AWTEvent class is the highest-level class in the AWT event-class hierarchy.

44. When a thread is created and started, what is its initial state?

A thread is in the ready state after it has been created and started.

45. Can an anonymous class be declared as implementing an interface and extending a class?

An anonymous class may implement an interface or extend a superclass, but may not be declared to do both.

46. What is the immediate superclass of Menu?

MenuItem

47. What is the purpose of finalization?

The purpose of finalization is to give an unreachable object the opportunity to perform any cleanup processing before the object is garbage collected.

48. Which class is the immediate superclass of the MenuComponent class?

Object.

49. What invokes a thread's run() method?

After a thread is started, via its start() method or that of the Thread class, the JVM invokes the thread's run() method when the thread is initially executed.

50. What is the difference between the Boolean & operator and the && operator?

If an expression involving the Boolean & operator is evaluated, both operands are evaluated. Then the & operator is applied to the operand. When an expression involving the && operator is evaluated, the first operand is evaluated.

If the first operand returns a value of true then the second operand is evaluated. The && operator is then applied to the first and second operands. If the first operand evaluates to false, the evaluation of the second operand is skipped.

Basics Interview Questions Of Java For Beginners Part-4

1. What is the difference between a constructor and a method?

A constructor is a member function of a class that is used to create objects of that class. It has the same name as the class itself, has no return type, and is invoked using the new operator. A method is an ordinary member function of a class. It has its own name, a return type (which may be void), and is invoked using the dot operator.

2. What is the purpose of garbage collection in Java, and when is it used?

The purpose of garbage collection is to identify and discard objects that are no longer needed by a program so that their resources can be reclaimed and reused.

A Java object is subject to garbage collection when it becomes unreachable to the program in which it is used.

3. Describe synchronization in respect to multithreading.

With respect to multithreading, synchronization is the capability to control the access of multiple threads to shared resources.

Without synchonization, it is possible for one thread to modify a shared variable while another thread is in the process of using or updating same shared variable. This usually leads to significant errors.

4. What is an abstract class?

Abstract class must be extended/subclassed (to be useful). It serves as a template. A class that is abstract may not be instantiated (ie. you may not call its constructor), abstract class may contain static data.

Any class with an abstract method is automatically abstract itself, and must be declared as such. A class may be declared abstract even if it has no abstract methods. This prevents it from being instantiated.

5. What is the difference between an Interface and an Abstract class?

An abstract class can have instance methods that implement a default behavior. An Interface can only declare constants and instance methods, but cannot implement default behavior and all methods are implicitly abstract.

An interface has all public members and no implementation. An abstract class is a class which may have the usual flavors of class members (private, protected, etc.), but has some abstract methods.

6. Explain different way of using thread?

The thread could be implemented by using runnable interface or by inheriting from the Thread class. The former is more advantageous, 'cause when you are going for multiple inheritance, the only interface can help

7. What is an Iterator?

Some of the collection classes provide traversal of their contents via a java.util.Iterator interface. This interface allows you to walk through a collection of objects, operating on each object in turn.

Remember when using Iterators that they contain a snapshot of the collection at the time the Iterator was obtained; generally it is not advisable to modify the collection itself while traversing an Iterator.

8. State the significance of public, private, protected, default modifiers both singly and in

combination and state the effect of package relationships on declared items qualified by these

modifiers.


public: Public class is visible in other packages, field is visible everywhere (class must be public too)

private : Private variables or methods may be used only by an instance of the same class that declares the variable or method, A private feature may only be accessed by the class that owns the feature.

protected : Is available to all classes in the same package and also available to all subclasses of the class that owns the protected feature. This access is provided even to subclasses that reside in a different package from the class that owns the protected feature.

What you get by default ie, without any access modifier (ie, public private or protected). It means that it is visible to all within a particular package.

9. What is static in java?

Static means one per class, not one for each object no matter how many instance of a class might exist. This means that you can use them without creating an instance of a class.Static methods are implicitly final, because overriding is done based on the type of the object, and static methods are attached to a class, not an object.

A static method in a superclass can be shadowed by another static method in a subclass, as long as the original method was not declared final. However, you can't override a static method with a nonstatic method. In other words, you can't change a static method into an instance method in a subclass.

10. What is final class?

A final class can't be extended ie., final class may not be subclassed. A final method can't be overridden when its class is inherited. You can't change value of a final variable (is a constant).

11. What if the main() method is declared as private?

The program compiles properly but at runtime it will give "main() method not public." message.

12. What if the static modifier is removed from the signature of the main() method?

Program compiles. But at runtime throws an error "NoSuchMethodError"

13. What if I write static public void instead of public static void?

Program compiles and runs properly.

14. What if I do not provide the String array as the argument to the method?

Program compiles but throws a runtime error "NoSuchMethodError".

15. What is the first argument of the String array in main() method?

The String array is empty. It does not have any element. This is unlike C/C++ where the first element by default is the program name.

16. If I do not provide any arguments on the command line, then the String array of main() method will be empty or null?

It is empty. But not null.

17. How can one prove that the array is not null but empty using one line of code?

Print args.length. It will print 0. That means it is empty. But if it would have been null then it would have thrown a NullPointerException on attempting to print args.length.

18. What environment variables do I need to set on my machine in order to be able to run Java

programs?

CLASSPATH and PATH are the two variables.

19. Can an application have multiple classes having main() method?

Yes it is possible. While starting the application we mention the class name to be run. The JVM will look for the Main method only in the class whose name you have mentioned. Hence there is not conflict amongst the multiple classes having main() method.

20. Can I have multiple main() methods in the same class?

No the program fails to compile. The compiler says that the main() method is already defined in the class.

21. Do I need to import java.lang package any time? Why ?

No. It is by default loaded internally by the JVM.

22. Can I import same package/class twice? Will the JVM load the package twice at runtime?

One can import the same package or same class multiple times. Neither compiler nor JVM complains about it. And the JVM will internally load the class only once no matter how many times you import the same class.

23. What are Checked and UnChecked Exception?

A checked exception is some subclass of Exception (or Exception itself), excluding class  RuntimeException and its subclasses. Making an exception checked forces client programmers to
deal with the possibility that the exception will be thrown.

Example: IOException thrown by java.io.FileInputStream's read() method·


Unchecked exceptions are RuntimeException and any of its subclasses. Class Error and its subclasses also are unchecked. With an unchecked exception, however, the compiler doesn't force client programmers either to catch the exception or declare it in a throws clause. In fact, client programmers  may not even know that the exception could be thrown.

Example: StringIndexOutOfBoundsException thrown by String's charAt() method· Checked exceptions must be caught at compile time. Runtime exceptions do not need to be. Errors often cannot be.

24. What is Overriding?

When a class defines a method using the same name, return type, and arguments as a method in its superclass, the method in the class overrides the method in the superclass.

When the method is invoked for an object of the class, it is the new definition of the method that is called, and not the method definition from superclass. Methods may be overridden to be more public, ot more private

25. Are the imports checked for validity at compile time? Example: will the code containing an import such as java.lang.ABCD compile?

Yes the imports are checked for the semantic validity at compile time. The code containing above line of import will not compile. It will throw an error saying, can not resolve symbol

symbol : class ABCD

location: package io

import java.io.ABCD;

' 26. Does importing a package imports the subpackages as well? Example: Does importing 
com.MyTest.* also import com.MyTest.UnitTests.*?

No you will have to import the subpackages explicitly. Importing com.MyTest.* will import classes in the package MyTest only. It will not import any class in any of it's subpackage.

27. What is the difference between declaring a variable and defining a variable?

In declaration we just mention the type of the variable and it's name. We do not initialize it. But
defining means declaration + initialization.

Example: String s; is just a declaration while String s = new String ("abcd"); Or String s = "abcd"; are both definitions.

28. What is the default value of an object reference declared as an instance variable?

The default value will be null unless we define it explicitly.

29. Can a top level class be private or protected?

No. A top level class cannot be private or protected. It can have either "public" or no modifier. If it does not have a modifier it is supposed to have a default access.

If a top level class is declared as private the compiler will complain that the "modifier private is not allowed here". This means that a top level class can not be private. Same is the case with  protected.

30. What type of parameter passing does Java support?

In Java the arguments are always passed by value

Basics Interview Questions Of Java For Beginners Part-3

Question 51:- Describe the different stages in the life cycle of an applet.

Answer:- The stages in the life cycle of an applet are-

1. Born or initialization state

2. Running state

3. Idle state

4. Dead or destroyed state

Born or initialization state: - Applet enters the initialization state when it is first loaded. This is achieved by calling the init () method of Applet class. The applet is born. At this stage, we may do the following if required

a) Create objects needed by the applet

b) Set up initial values

c) Load images or fonts

d) Set up colors

The initialization occurs only once in the applet’s life cycle. To provide any of the behaviours ,we must override the init() method.

Running state: - Applet enters the running state when the system calls the start( ) method of Applet Class. This occurs automatically after the applet is initialized. Starting can also occur if the Applet is already in ‘stopped” ( idle) state. For example, we may leave the web page containing the applet temporarily to another page and return back to the page. This again starts the applet running. Note that, unlike init( ) method, the start( ) method may be called more than once. We may override the start( ) method to create a thread to control the applet.

Idle or stopped state: - An applet becomes idle when it is stopped from running. Stopping occurs automatically when we leave the page containing the currently running applet. We can also do so by calling the stop( ) method explicitly. If we use a thread to run the applet, then we must use stop( ) method to terminate the thread. We can achieve this by overriding the stop( ) method;

Dead state: - An applet is said to be dead when it is removed from memory. This occurs automatically by invoking the destroy( ) method when we quit the browser. Like initialization, destroying stage occurs only once in the applet’s life cycle. If the applet has created any resources, like threads, we may override the destroy( ) method to clean up these resources.

Question 52 :- What is event handling?

Answer :- Event handling is a mechanism that is used to handle events generated by applets. An event could be the occurrence of any activity such as a mouse click or a key press. In java, events are regarded as method calls with a certain task performed against the occurrence of each event.

Question 53:- Name some of the key events?

Answer:- Some of the key events are:

1.ActionEvent is triggered whenever a user interface element is activated, such as selection of a menu item.

2. ItemEvent is triggered at the selection or deselection of an itemized or list element, such as checkbox.

3. TextEvent is triggered when a text field is modified.

4. WindowEvent is triggered whenever a window – related operation is performed, such as closing or activating a window.

Question 54:- Define Event Listeners.

Answer:- The event listener object contains methods for receiving and processing event notifications sent by the source object. These methods are implemented from the corresponding listener interface contained in the java.awt.event package.

Question 55 :-Define Event Classes.

Answer:- All the events in java have corresponding event classes associated with item. Each of these classes is derived from one single super class, i.e., EventObject. It is contained in the java.util package. The EventObject class contains the following two important methods for handling events:

1. getSource(): Returns the event source.

2. toString (): Returns a string containing information about the event source.

Question 56: How is java’s coordinate system organized?

Answer:- Java’s coordinate system has the origin (0, 0) in the upper–left corner. Positive x values are to the right, and positive y values are to the bottom. The values of coordinates x and y are in pixels.

Question 57:- Describe the arguments used in the method drawRoundRect( ).

Answer:- The drawRoundRect() method takes 6 arguments:-The first two represent the x and y coordinates of the top left corner of the rectangle,and the next two represent the width and the height of the rectangle and the remaining two represent the width and height of the angle of corners.

Question 58 :- What is AWT?

Answer:-The Abstract Windowing Toolkit ( AWT) IS AN APL that is responsible for building the Graphical User Interface ( GUI). It is a part of java Foundation Classes (JFC). AWT includes a rich set of user interface components, a powerful event handling model, graphics and image tools, layout managers and support for data transfer using cut and paste through clipboards. AWT also supports JavaBeans architecture. Every AWT component is a simple bean. The java.awt package contains all classes for creating user interfaces and for painting graphics and image.

Question 59 :- What is Component?

Answer:- Component class is the super class to all the class to all the other classes from which various GUI elements are realized. It is primary responsible for effecting the display of a graphic object on the screen. It also handles the various keyboard and mouse events of the GUI application.

Question 60:- What is Container?

Answer:- The Container object contains the other awt components. It manages the layout and placement of the various awt components within the container. A container object can contain other containers objects as well; thus allowing nesting of containers.

Question 61:- What is Window?

Answer:- The Window object realizes a top-level window but without any border or menu bar. It just specifies the layout of the window. A typical window that you would want to create in your application is not normally derived from the Window class but from its subclass, i.e., Frame.

Question 62:- What is Panel?

Answer:- The super class of applet, Panel represents a window space on which the application’s output is displayed. It is just like a normal window having no border, title bar, menu bar, etc. A panel can contain within itself other panels as.

Question 63 :-What is Frame?

Answer:- The Frame object realizes a top-level window complete with border and menu bar. It supports common window- related events such as close, open, activate, deactivate, etc. Almost all the programs that we created while discussing applets and graphics programming used one or more classes of the awt packaged.

Question 64:- Describe the arguments used in the method drawRoundRect ().

Answer:- The arguments used are the first two represent the x and y coordinates of the top left corner of the rectangle and the next two represent the width and height of the rectangle and the remaining two represent the width and height of the angle of the corners.

Question 65:- What is an Error?

Answer:- An error may produce an incorrect output or may terminate the execution of the program abruptly or even may cause in the program will not terminate or crash during execution.

Question 66 :- What are the types of Errors?

Answer:- Errors may broadly be classified into two categories:

1. Compile-time errors:- All syntax errors will be detected and displayed by the java compiler and therefore these errors are known as compile-time errors. Whenever the Compiler displays an error, it will not create the class file. It is therefore necessary that we fix all the errors before we can successfully compile and run the program.

2. Run-time errors:- Sometimes, a program may compile successfully creating the .class file but may not run properly. Such programs may produce wrong results due to wrong logic or may terminate due to errors such as stack overflow. This is called Run-time errors.

Question 67 :- Define exception.

Answer :- An exception is a condition that is caused by a run-time error in the program. When the java interpreter encounters an error such as dividing an integer by zero, it creates an exception object and throws it (i.e. informs us that an error has occurred. The purpose of exception handling mechanism is to provide a means to detect and report an “exceptional circumstance” so that appropriate action can be taken.

Question 68 :- How is Exceptions in java categorized?

Answer :- Exceptions in java can be categorised into two types:

1.Checked exceptions: These exceptions are exceptions are explicitly handled in the code itself with the help of try- catch blocks. Checked exceptions are extended from the java.lang.Eception class.

2. Unchecked exceptions: These exceptions are not essentially handed in the program code; instead the JVM handles such exceptions. Unchecked exceptions are extended from the java.lang.RuntimeException class.

Question 69 :- What is Persistent data?

Answer :- Data stored in files is often called Persistent data.

' Question 70 :- What is Object serialization?

Answer :- The process of reading and writing objects is called object serialization.

Question 71 :- What is a file?

Answer :- A file is a collection of related records placed in a particular area on disk.

Question 72 :- What is a record?

Answer :- A record is composed of several fields and a field is a group of characters.

Question 73 :- What is file processing?

Answer :- Storing and managing data using files is known as file processing which includes tasks such as creating files, updating files and manipulation of data.

Question 74:-What is a stream?

Answer:- A stream in java is a path along which data flows (like a river or a pipe along which water flows). It has a source (of data) and a destination (for that data).

Question 75 :- How is the concept of steams used in java?

Answer:- The concept of sending data from one stream to another (like one pipe feeding into another pipe) has made streams in java a powerful tool for file processing.

Question 76 :- What are input and output streams?

Answer:- Java streams are classified into two basic types, namely, input stream and output stream. An input stream extracts (i.e. reads) data from the source (file) and sends it to the program. Similarly, an output stream takes data from the program and sends (i.e. writes) it to the destination (file).

Question 77:- What is stream class? How are the stream class classified?

Answer:- The java.io package contains a large number of stream classes that provide capabilities for processing all types of data. These classes may be categorized into two groups based on the data type on which they operate.

1.Byte stream classes that provide support for handling I/O operations on bytes.

2. Character stream classes that provide support for managing I/O operations on characters.

Question 78:- Describe the major tasks of input and output stream classes.

Answer :- The super class InputStream is an abstract class, and, therefore, we cannot create instances of this class. Rather, we must use the subclasses that inherit from this class.

The InputStream class defines methods for performing input functions such as

1 Reading bytes

2 Closing streams

3 Marking Positions in streams

4 Skipping ahead in a stream

5 Finding the number of bytes in a stream

Outputstream is an abstract class and therefore we cannot instantiate it. The several subclasses of the OutputStream can be used for performing the output operations.

The Ouptputstream includes methods that are designed to perform the following tasks:

1 Writing bytes

2 Closing streams

3 Flushing streams

Question 79:- What is reader stream class?

Answer:- Reader stream classes are designed to read character from the files. The Reader class contains methods that are identical to those available in the Inputstream class, except reader is designed to handle characters.

Question 80 :- What is writer stream classes?

Answer:- The writer class is an abstract class which acts as a base class for all the other writer stream classes.

Question 81:- What is RandomAccessFile?

Answer:- The RandomAccessFile enables us to read and write bytes, text and java data types to any location in a file (when used with appropriate access permissions). This class extends object class and implements DataInput and Dataoutput interfaces. This forces the RandomAccessFile to implement the methpods described in both these interfaces.


Question 82:- What is Stream Tokenizer?

Answer:- The class Stream Tokenizer, a subclass of object can be used for breaking up a stream of text from an input text file into meaningful pieces called tokens. The behaviour of the Stream Tokenizer class is similar to that of the String Tokenizer class (of java.util Package) that breaks a string into its component tokens.

Question 83:-What is file class?

Answer:- The java.io package includes a class known as the File class that provides support for creating files and directories.

The class includes several constructors for maintaining the file objects. This class also contains several methods for  supporting the operations such as

1 Creating a file

2 Opening a file

3 Closing a file

4 Deleting a file

5 Getting a name of a file

6 Getting the size of a file

7 Checking the existence of a file

8 Renaming of a file

9 Checking whether the file is writable

1o Checking whether the file is readable