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
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
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
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 value 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
18. What modifiers may be used with an inner class that is a member of an outer
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
22. How many bits are used to represent Unicode, ASCII, UTF-16, and UTF-8
Unicode requires 16 bits and ASCII require 7 bits. Although the ASCII character
set uses only 7 bits, it is usually represented as 8 bits. UTF-8 represents
characters using 8, 16, and 18 bit patterns. UTF-16 uses 16-bit and larger bit
23 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.
24. Which java.util classes and interfaces support event handling?
The EventObject class and the EventListener interface support event processing.
25. Is sizeof a keyword?
The sizeof operator is not a keyword.
26. What are wrapper classes?
Wrapper classes are classes that allow primitive types to be accessed as
27. 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.
28. 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).
29. 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.
30. What is the immediate superclass of the Applet class?
31. What is the difference between preemptive scheduling and time slicing?
Under preemptive 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 reenters
the pool of ready tasks. The scheduler then determines which task should execute
next, based on priority and other factors.
32. Name three Component subclasses that support painting.
The Canvas, Frame, Panel, and Applet classes support painting.
33. 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.
34. What is the immediate superclass of the Dialog class?
35. What is clipping?
Clipping is the process of confining paint operations to a limited area or
36. What is a native method?
A native method is a method that is implemented in a language other than Java.
37. Can a for statement loop indefinitely?
Yes, a for statement can loop indefinitely. For example, consider the following:
38. 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. Associatity determines whether an expression is evaluated
left-to-right or right-to-left
39. When a thread blocks on I/O, what state does it enter?
A thread enters the waiting state when it blocks on I/O.
40. To what value is a variable of the String type automatically initialized?
The default value of a String type is null.
41. 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.
42. 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.
43. 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.
44. 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
45. 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.
46. 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.
47. What is the range of the short type?
The range of the short type is -(2^15) to 2^15 - 1.
48. What is the range of the char type?
The range of the char type is 0 to 2^16 - 1.
49. In which package are most of the AWT events that support the
event-delegation model defined?
Most of the AWT-related events of the event-delegation model are defined in the
java.awt.event package. The AWTEvent class is defined in the java.awt package.
50. What is the immediate superclass of Menu?
51. 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.
52. Which class is the immediate superclass of the MenuComponent class.
53. 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.
54. 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.
55. Name three subclasses of the Component class.
Box.Filler, Button, Canvas, Checkbox, Choice, Container, Label, List, Scrollbar,
56. What is the GregorianCalendar class?
The GregorianCalendar provides support for traditional Western calendars.
57. Which Container method is used to cause a container to be laid out and
58. What is the purpose of the Runtime class?
The purpose of the Runtime class is to provide access to the Java runtime
59. How many times may an object's finalize() method be invoked by the
An object's finalize() method may only be invoked once by the garbage collector.
60. 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.
61. What is the argument type of a program's main() method?
A program's main() method takes an argument of the String type.
62. Which Java operator is right associative?
The = operator is right associative.
63. What is the Locale class?
The Locale class is used to tailor program output to the conventions of a
particular geographic, political, or cultural region.64. Can a double value be
cast to a byte?
Yes, a double value can be cast to a byte.
65. What is the difference between a break statement and a continue statement?
A break statement results in the termination of the statement to which it
applies (switch, for, do, or while). A continue statement is used to end the
current loop iteration and return control to the loop statement.
66. 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.
67. What method is invoked to cause an object to begin executing as a separate
The start() method of the Thread class is invoked to cause an object to begin
executing as a separate thread.
68. Name two subclasses of the TextComponent class.
TextField and TextArea
69. What is the advantage of the event-delegation model over the earlier
The event-delegation model has two advantages over the event-inheritance model.
First, it enables event handling to be handled by objects other than the ones
that generate the events (or their containers). This allows a clean separation
between a component's design and its use. The other advantage of the
event-delegation model is that it performs much better in applications where
many events are generated. This performance improvement is due to the fact that
the event-delegation model does not have to repeatedly process unhandled events,
as is the case of the event-inheritance
70. Which containers may have a MenuBar?
71. How are commas used in the initialization and iteration parts of a for
Commas are used to separate multiple statements within the initialization and
iteration parts of a for statement.
72. 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.
73. What is an abstract method?
An abstract method is a method whose implementation is deferred to a subclass.
74. 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.
75. 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.
76. What are the high-level thread states?
The high-level thread states are ready, running, waiting, and dead.
77. 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.
78. Can a Byte object be cast to a double value?
No, an object cannot be cast to a primitive value.
79. 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
80. What is the difference between the String and StringBuffer classes?
String objects are constants. StringBuffer objects are not.
81. 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
82. What is an object's lock and which objects 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.
83. What is the Dictionary class?
The Dictionary class provides the capability to store key-value pairs.
84. 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.
85. 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.
86. 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.
87. 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.
88. Which class is extended by all other classes?
The Object class is extended by all other classes.
89. Can an object be garbage collected while it is still reachable?
A reachable object cannot be garbage collected. Only unreachable objects may be
90. Is the ternary operator written x : y ? z or x ? y : z ?
It is written x ? y : z.
91. 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.
92. How is rounding performed under integer division?
The fractional part of the result is truncated. This is known as rounding toward
93. 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.
94. 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.
95. 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.
96. If a class is declared without any access modifiers, where may the class be
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.
97. What is the SimpleTimeZone class?
The SimpleTimeZone class provides support for a Gregorian calendar.
98. What is the Map interface?
The Map interface replaces the JDK 1.1 Dictionary class and is used associate
keys with values.99. Does a class inherit the constructors of its superclass?
A class does not inherit constructors from any of its super classes.
100. 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.
101. What is the purpose of the System class?
The purpose of the System class is to provide access to system resources.
102. Which TextComponent method is used to set a TextComponent to the read-only
103. How are the elements of a CardLayout organized?
The elements of a CardLayout are stacked, one on top of the other, like a deck
104. Is &&= a valid Java operator?
No, it is not.
105. Name the eight primitive Java types.
The eight primitive types are byte, char, short, int, long, float, double, and
106. 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.
107. 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.
108. Is "abc" a primitive value?
The String literal "abc" is not a primitive value. It is a String object.
109. What is the relationship between an event-listener interface and an
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.
110. What restrictions are placed on the values of each case of a switch
During compilation, the values of each case of a switch statement must evaluate
to a value that can be promoted to an int value.
111. What modifiers may be used with an interface declaration?
An interface may be declared as public or abstract.
112. Is a class a subclass of itself?
A class is a subclass of itself.
113. 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.
114. What event results from the clicking of a button?
The ActionEvent event is generated as the result of the clicking of a button.
115. 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.
116. What is the difference between a while statement and a do statement?
A while statement checks at the beginning of a loop to see whether the next loop
iteration should occur. A do statement checks at the end of a loop to see
whether the next iteration of a loop should occur. The do statement will always
execute the body of a loop at least once.
117. 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.
118. What advantage do Java's layout managers provide over traditional windowing
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 accommodate platform-specific
differences among windowing systems.
119. 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
120. What modifiers can be used with a local inner class?
A local inner class may be final or abstract.
121. 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.
122. 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.
123. 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.
124. Can an exception be rethrown?
Yes, an exception can be rethrown.
125. Which Math method is used to calculate the absolute value of a number?
The abs() method is used to calculate absolute values.
126. 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.
127. When does the compiler supply a default constructor for a class?
The compiler supplies a default constructor for a class if no other constructors
128. 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.
129. Which class is the immediate superclass of the Container class?
130. 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.
131. How can the Checkbox class be used to create a radio button?
By associating Checkbox objects with a CheckboxGroup.
132. Which non-Unicode letter characters may be used as the first character of
The non-Unicode letter characters $ and _ may appear as the first character of
133. What restrictions are placed on method overloading?
Two methods may not have the same name and argument list but different return
134. 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
135. 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.
136. What is the return type of a program's main() method?
A program's main() method has a void return type.
137. Name four Container classes.
Window, Frame, Dialog, FileDialog, Panel, Applet, or ScrollPane
138. 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.
139. What class of exceptions are generated by the Java run-time system?
The Java runtime system generates RuntimeException and Error exceptions.
140. What class allows you to read objects directly from a stream?
The ObjectInputStream class supports the reading of objects from input streams.
141. 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.
142. Under what conditions is an object's finalize() method invoked by the
The garbage collector invokes an object's finalize() method when it detects that
the object has become unreachable.
143. How are this () and super () used with constructors?
this() is used to invoke a constructor of the same class. super() is used to
invoke a superclass constructor.
144. 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.
145. 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
146. 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.
147. Why are the methods of the Math class static?
So they can be invoked as if they are a mathematical code library.
148. What Checkbox method allows you to tell if a Checkbox is checked?
149. What state is a thread in when it is executing?
An executing thread is in the running state.
150. 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.
151. How are the elements of a GridLayout organized?
The elements of a GridBad layout are of equal size and are laid out using the
squares of a grid.
152. 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
153. 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
154. 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.
155. 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
156. What are E and PI?
E is the base of the natural logarithm and PI is mathematical value pi.
157. Are true and false keywords?
The values true and false are not keywords.
158. What is a void return type?
A void return type indicates that a method does not return a value.
159. 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.
160. 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.
161. What happens when you add a double value to a String?
The result is a String object.162. What is your platform's default character
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..
163. Which package is always imported by default?
The java.lang package is always imported by default.
164. 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.
165. 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.
166. What is the purpose of garbage collection?
The purpose of garbage collection is to identify and discard objects that are no
longer needed by a program so that their resources may be reclaimed and
167. What is a compilation unit?
A compilation unit is a Java source code file.
168. What interface is extended by AWT event listeners?
All AWT event listeners extend the java.util.EventListener interface.
169. 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.
170. How can a dead thread be restarted?
A dead thread cannot be restarted.
171. 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.
172. What is a layout manager?
A layout manager is an object that is used to organize components in a
173. Which arithmetic operations can result in the throwing of an
Integer / and % can result in the throwing of an ArithmeticException.
174. 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.
175. Can an abstract class be final?
An abstract class may not be declared as final.176. What is the ResourceBundle
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.
177. 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.
178. 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.
179. 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.
180. 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.
181. To what value is a variable of the boolean type automatically initialized?
The default value of the boolean type is false.
182. Can try statements be nested?
Try statements may be tested.
183. What is the difference between the prefix and postfix forms of the ++
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.
184. What is the purpose of a statement block?
A statement block is used to organize a sequence of statements as a single
185. 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.
186. What modifiers may be used with a top-level class?
A top-level class may be public, abstract, or final.
187. 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
188. 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.
189. 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.190. 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.
191. 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.
192. What methods are used to get and set the text label displayed by a Button
getLabel() and setLabel()
193. Which Component subclass is used for drawing and painting?
194. 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 statement195. 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
196. What are the problems faced by Java programmers who don't use layout
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
197. What is the difference between an if statement and a switch statement?
The if statement is used to select among two alternatives. It uses a boolean
expression to decide which alternative should be executed. The switch statement
is used to select among multiple alternatives. It uses an int expression to
determine which alternative should be executed.