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.
