1.what is a transient variable?
Atransient variable is a variable that may not be serialized.
2.whichcontainers use a border Layout as their default layout?
Thewindow, Frame and Dialog classes use a border layout as their default layout.
3.Whydo threads block on I/O?
Threadsblock on i/o (that is enters the waiting state) so that other threads mayexecute
whilethe i/o
Operationis performed.
4.How are Observer and Observable used?
Objectsthat subclass the Observable class maintain a list of observers. When an
Observableobject is
updatedit invokes the update() method of each of its observers to notify the observers
thatit has changed
state.The Observer interface is implemented by objects that observe Observableobjects.
5.What is synchronization and why is it important?
Withrespect to multithreading, synchronization is the capability to control theaccess of
multiplethreads to
sharedresources. Without synchronization, it is possible for one thread to modify a
sharedobject while
anotherthread is in the process of using or updating that object's value. This oftenleads
tosignificant
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 Classobject.
7.What's new with the stop(), suspend() and resume() methods in JDK 1.2?
Thestop(), suspend() and resume() methods have been deprecated in JDK 1.2.
8.Is null a keyword?
Thenull value is not a keyword.
9.What is the preferred size of a component?
Thepreferred size of a component is the minimum component size that will allow the
componentto display
normally.
10.What method is used to specify a container's layout?
ThesetLayout() method is used to specify a container's layout.
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11.Which containers use a FlowLayout as their default layout?
ThePanel and Applet classes use the FlowLayout as their default layout.
12.What state does a thread enter when it terminates its processing?
Whena thread terminates its processing, it enters the dead state.
13.What is the Collections API?
TheCollections API is a set of classes and interfaces that support operations on
collectionsof objects.
14.Which characters may be used as the second character of an identifier, but not
asthe first
characterof an identifier?
Thedigits 0 through 9 may not be used as the first character of an identifier butthey may
beused after the
firstcharacter of an identifier.
15.What is the List interface?
TheList interface provides support for ordered collections of objects.
16.How does Java handle integer overflows and underflows?
Ituses those low order bytes of the result that can fit into the size of the typeallowed by
theoperation.
17.What is the Vector class?
TheVector 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?
TheIterator 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
beenshifted out.
21.Which method of the Component class is used to set the position and size of a
component?
setBounds()
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22.How many bits are used to represent Unicode, ASCII, UTF-16, and UTF-8
characters?
Unicoderequires 16 bits and ASCII require 7 bits. Although the ASCII character setuses
only7 bits, it is
usuallyrepresented as 8 bits. UTF-8 represents characters using 8, 16, and 18 bitpatterns.
UTF-16uses 16-
bitand larger bit patterns.
23Whatis the difference between yielding and sleeping?
Whena task invokes its yield() method, it returns to the ready state. When a taskinvokes
itssleep()
method,it returns to the waiting state.
24.Which java.util classes and interfaces support event handling?
TheEventObject class and the EventListener interface support event processing.
25.Is sizeof a keyword?
Thesizeof operator is not a keyword.
26.What are wrapped classes?
Wrappedclasses are classes that allow primitive types to be accessed as objects.
27.Does garbage collection guarantee that a program will not run out of memory?
Garbagecollection does not guarantee that a program will not run out of memory. It is
possiblefor
programsto use up memory resources faster than they are garbage collected. It is also
possiblefor
programsto create objects that are not subject to garbage collection
28.What restrictions are placed on the location of a package statement within a
sourcecode file?
Apackage statement must appear as the first line in a source code file(excluding blank
linesand
comments).
29.Can an object's finalize() method be invoked while it is reachable?
Anobject's finalize() method cannot be invoked by the garbage collector while theobject
isstill reachable.
However,an object's finalize() method may be invoked by other objects.
30.What is the immediate superclass of the Applet class?
Panel
31.What is the difference between preemptive scheduling and time slicing?
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Underpreemptive scheduling, the highest priority task executes until it enters thewaiting
ordead states or
ahigher priority task comes into existence. Under time slicing, a task executesfor a
predefinedslice of
timeand then reenters the pool of ready tasks. The scheduler then determines whichtask
shouldexecute
next,based on priority and other factors.
32.Name three Component subclasses that support painting.
TheCanvas, Frame, Panel, and Applet classes support painting.
33.What value does readLine() return when it has reached the end of a file?
ThereadLine() method returns null when it has reached the end of a file.
34.What is the immediate superclass of the Dialog class?
Window
35.What is clipping?
Clippingis the process of confining paint operations to a limited area or shape.
36.What is a native method?
Anative 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:
for(;;);
38.What are order of precedence and associativity, and how are they used?
Orderof precedence determines the order in which operators are evaluated in
expressions.Associatity
determineswhether an expression is evaluated left-to-right or right-to-left
39.When a thread blocks on I/O, what state does it enter?
Athread enters the waiting state when it blocks on I/O.
40.To what value is a variable of the String type automatically initialized?
Thedefault value of an String type is null.
41.What is the catch or declare rule for method declarations?
Ifa checked exception may be thrown within the body of a method, the method must
eithercatch the
exceptionor declare it in its throws clause.
42.What is the difference between a MenuItem and a CheckboxMenuItem?
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TheCheckboxMenuItem class extends the MenuItem class to support a menu item that
maybe checked or
unchecked.
43.What is a task's priority and how is it used in scheduling?
Atask's priority is an integer value that identifies the relative order in whichit should be
executedwith
respectto other tasks. The scheduler attempts to schedule higher priority tasks before
lowerpriority tasks.
44.What class is the top of the AWT event hierarchy?
Thejava.awt.AWTEvent class is the highest-level class in the AWT event-class
hierarchy.
45.When a thread is created and started, what is its initial state?
Athread is in the ready state after it has been created and started.
46.Can an anonymous class be declared as implementing an interface and
extendinga class?
Ananonymous class may implement an interface or extend a superclass, but may notbe
declaredto do
both.
47.What is the range of the short type?
Therange of the short type is -(2^15) to 2^15 - 1.
48.What is the range of the char type?
Therange 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
modeldefined?
Mostof the AWT-related events of the event-delegation model are defined in the
java.awt.eventpackage.
TheAWTEvent class is defined in the java.awt package.
50.What is the immediate superclass of Menu?
MenuItem
51.What is the purpose of finalization?
Thepurpose of finalization is to give an unreachable object the opportunity toperform
anycleanup
processingbefore the object is garbage collected.
52.Which class is the immediate superclass of the MenuComponent class.
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Object
53.What invokes a thread's run() method?
Aftera thread is started, via its start() method or that of the Thread class, theJVM
invokesthe thread's
run()method when the thread is initially executed.
54.What is the difference between the Boolean & operator and the &&operator?
Ifan expression involving the Boolean & operator is evaluated, both operandsare
evaluated.Then the &
operatoris applied to the operand. When an expression involving the && operatoris
evaluated,the first
operandis evaluated. If the first operand returns a value of true then the secondoperand
isevaluated. The
&&operator is then applied to the first and second operands. If the first operand
evaluatesto false, the
evaluationof the second operand is skipped.
55.Name three subclasses of the Component class.
Box.Filler,Button, Canvas, Checkbox, Choice, Container, Label, List, Scrollbar, or
TextComponent
56.What is the GregorianCalendar class?
TheGregorianCalendar provides support for traditional Western calendars.
57.Which Container method is used to cause a container to be laid out and
redisplayed?
validate()
58.What is the purpose of the Runtime class?
Thepurpose of the Runtime class is to provide access to the Java runtime system.
59.How many times may an object's finalize() method be invoked by the garbage
collector?
Anobject'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?
Thefinally clause is used to provide the capability to execute code no matterwhether or
notan exception is
thrownor caught.
61.What is the argument type of a program's main() method?
Aprogram's main() method takes an argument of the String[] type.
62.Which Java operator is right associative?
The= operator is right associative.
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63.What is the Locale class?
TheLocale class is used to tailor program output to the conventions of aparticular
geographic,political, or
culturalregion.
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?
Abreak statement results in the termination of the statement to which it applies(switch,
for,do, or while).
Acontinue statement is used to end the current loop iteration and return controlto the
loopstatement.
66.What must a class do to implement an interface?
Itmust provide all of the methods in the interface and identify the interface inits
implementsclause.
67.What method is invoked to cause an object to begin executing as a separate
thread?
Thestart() method of the Thread class is invoked to cause an object to beginexecuting as
aseparate thread.
68.Name two subclasses of the TextComponent class.
TextFieldand TextArea
69.What is the advantage of the event-delegation model over the earliereventinheritance
model?
Theevent-delegation model has two advantages over the event-inheritance model.First,
itenables event
handlingto be handled by objects other than the ones that generate the events (or their
containers).This
allowsa clean separation between a component's design and its use. The otheradvantage
ofthe eventdelegation
modelis that it performs much better in applications where many events are
generated.This
performanceimprovement is due to the fact that the event-delegation model does not
haveto repeatedly
processunhandled events, as is the case of the event-inheritance model.
70.Which containers may have a MenuBar?
Frame
71.How are commas used in the initialization and iteration parts of a forstatement?
Commasare used to separate multiple statements within the initialization anditeration
partsof a for
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statement.
72.What is the purpose of the wait(), notify(), and notifyAll() methods?
Thewait(),notify(), and notifyAll() methods are used to provide an efficient wayfor
threadsto wait for a
sharedresource. When a thread executes an object's wait() method, it enters thewaiting
state.It only enters
theready state after another thread invokes the object's notify() or notifyAll()methods.
73.What is an abstract method?
Anabstract method is a method whose implementation is deferred to a subclass.
74.How are Java source code files named?
AJava source code file takes the name of a public class or interface that isdefined within
thefile. A source
codefile may contain at most one public class or interface. If a public class orinterface is
definedwithin a
sourcecode file, then the source code file must take the name of the public class or
interface.If no public
classor interface is defined within a source code file, then the file must take on aname
thatis different than
itsclasses and interfaces. Source code files use the .java extension.
75.What is the relationship between the Canvas class and the Graphics class?
ACanvas object provides access to a Graphics object via its paint() method.
76.What are the high-level thread states?
Thehigh-level thread states are ready, running, waiting, and dead.
77.What value does read() return when it has reached the end of a file?
Theread() 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?
Anon-static inner class may have object instances that are associated withinstances of
theclass's outer
class.A static inner class does not have any object instances.
80.What is the difference between the String and StringBuffer classes?
Stringobjects are constants. StringBuffer objects are not.
81.If a variable is declared as private, where may the variable be accessed?
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Aprivate variable may only be accessed within the class in which it is declared.
82.What is an object's lock and which object's have locks?
Anobject's lock is a mechanism that is used by multiple threads to obtainsynchronized
accessto the object.
Athread may execute a synchronized method of an object only after it hasacquired the
object'slock. All
objectsand classes have locks. A class's lock is acquired on the class's Class object.
83.What is the Dictionary class?
TheDictionary class provides the capability to store key-value pairs.
84.How are the elements of a BorderLayout organized?
Theelements of a BorderLayout are organized at the borders (North, South, East,and
West)and the center
ofa container.
85.What is the % operator?
Itis referred to as the modulo or remainder operator. It returns the remainder ofdividing
thefirst operand
bythe second operand.
86.When can an object reference be cast to an interface reference?
Anobject reference be cast to an interface reference when the object implementsthe
referencedinterface.
87.What is the difference between a Window and a Frame?
TheFrame class extends Window to define a main application window that can have a
menubar.
88.Which class is extended by all other classes?
TheObject class is extended by all other classes.
89.Can an object be garbage collected while it is still reachable?
Areachable object cannot be garbage collected. Only unreachable objects may be
garbagecollected..
90.Is the ternary operator written x : y ? z or x ? y : z ?
Itis written x ? y : z.
91.What is the difference between the Font and FontMetrics classes?
TheFontMetrics class is used to define implementation-specific properties, such as
ascentand descent, of a
Fontobject.
92.How is rounding performed under integer division?
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Thefractional part of the result is truncated. This is known as rounding towardzero.
93.What happens when a thread cannot acquire a lock on an object?
Ifa thread attempts to execute a synchronized method or synchronized statementand is
unableto acquire
anobject'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/
OutputStreamclass hierarchy?
TheReader/Writer class hierarchy is character-oriented, and the
InputStream/OutputStreamclass hierarchy
isbyte-oriented.
95.What classes of exceptions may be caught by a catch clause?
Acatch clause can catch any exception that may be assigned to the Throwabletype. This
includesthe Error
andException types.
96.If a class is declared without any access modifiers, where may the class be
accessed?
Aclass that is declared without any access modifiers is said to have packageaccess. This
meansthat the
classcan only be accessed by other classes and interfaces that are defined withinthe
samepackage.
97.What is the SimpleTimeZone class?
TheSimpleTimeZone class provides support for a Gregorian calendar.
98.What is the Map interface?
TheMap interface replaces the JDK 1.1 Dictionary class and is used associate keyswith
values.
99.Does a class inherit the constructors of its superclass?
Aclass does not inherit constructors from any of its superclasses.
100.For which statements does it make sense to use a label?
Theonly statements for which it makes sense to use a label are those statementsthat can
enclosea break or
continuestatement.
101.What is the purpose of the System class?
Thepurpose of the System class is to provide access to system resources.
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102.Which TextComponent method is used to set a TextComponent to the readonly
state?
setEditable()
103.How are the elements of a CardLayout organized?
Theelements of a CardLayout are stacked, one on top of the other, like a deck ofcards.
104.Is &&= a valid Java operator?
No,it is not.
105.Name the eight primitive Java types.
Theeight primitive types are byte, char, short, int, long, float, double, andboolean.
106.Which class should you use to obtain design information about an object?
TheClass class is used to obtain information about an object's design.
107.What is the relationship between clipping and repainting?
Whena window is repainted by the AWT painting thread, it sets the clipping regionsto
thearea of the
windowthat requires repainting.
108.Is "abc" a primitive value?
TheString literal "abc" is not a primitive value. It is a String object.
109.What is the relationship between an event-listener interface and aneventadapter
class?
Anevent-listener interface defines the methods that must be implemented by anevent
handlerfor a
particularkind of event. An event adapter provides a default implementation of aneventlistener
interface.
110.What restrictions are placed on the values of each case of a switch statement?
Duringcompilation, the values of each case of a switch statement must evaluate to a
valuethat can be
promotedto an int value.
111.What modifiers may be used with an interface declaration?
Aninterface may be declared as public or abstract.
112.Is a class a subclass of itself?
Aclass is a subclass of itself.
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113.What is the highest-level event class of the event-delegation model?
Thejava.util.EventObject class is the highest-level class in the event-delegationclass
hierarchy.
114.What event results from the clicking of a button?
TheActionEvent event is generated as the result of the clicking of a button.
115.How can a GUI component handle its own events?
Acomponent can handle its own events by implementing the required event-listener
interfaceand adding
itselfas its own event listener.
116.What is the difference between a while statement and a do statement?
Awhile statement checks at the beginning of a loop to see whether the next loopiteration
shouldoccur. A
dostatement checks at the end of a loop to see whether the next iteration of aloop should
occur.The do
statementwill always execute the body of a loop at least once.
117.How are the elements of a GridBagLayout organized?
Theelements of a GridBagLayout are organized according to a grid. However, the
elementsare of different
sizesand may occupy more than one row or column of the grid. In addition, the rowsand
columnsmay
havedifferent sizes.
118.What advantage do Java's layout managers provide over traditional windowing
systems?
Javauses layout managers to lay out components in a consistent manner across all
windowingplatforms.
SinceJava's layout managers aren't tied to absolute sizing and positioning, they areable
toaccomodate
platform-specificdifferences among windowing systems.
119.What is the Collection interface?
TheCollection interface provides support for the implementation of a mathematicalbag -
anunordered
collectionof objects that may contain duplicates.
120.What modifiers can be used with a local inner class?
Alocal inner class may be final or abstract.
121.What is the difference between static and non-static variables?
Astatic variable is associated with the class as a whole rather than withspecific instances
ofa class. Nonstatic
variablestake on unique values with each object instance.
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122.What is the difference between the paint() and repaint() methods?
Thepaint() method supports painting via a Graphics object. The repaint() method isused
tocause paint() to
beinvoked by the AWT painting thread.
123.What is the purpose of the File class?
TheFile class is used to create objects that provide access to the files anddirectories of a
localfile 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?
Theabs() method is used to calculate absolute values.
126.How does multithreading take place on a computer with a single CPU?
Theoperating system's task scheduler allocates execution time to multiple tasks.By
quicklyswitching
betweenexecuting tasks, it creates the impression that tasks execute sequentially.
127.When does the compiler supply a default constructor for a class?
Thecompiler supplies a default constructor for a class if no other constructorsare
provided.
128.When is the finally clause of a try-catch-finally statement executed?
Thefinally clause of the try-catch-finally statement is always executed unless thethread
ofexecution
terminatesor an exception occurs within the execution of the finally clause.
129.Which class is the immediate superclass of the Container class?
Component
130.If a method is declared as protected, where may the method be accessed?
Aprotected method may only be accessed by classes or interfaces of the samepackage or
bysubclasses of
theclass in which it is declared.
131.How can the Checkbox class be used to create a radio button?
Byassociating Checkbox objects with a CheckboxGroup.
132.Which non-Unicode letter characters may be used as the first character of an
identifier?
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Thenon-Unicode letter characters $ and _ may appear as the first character of an
identifier
133.What restrictions are placed on method overloading?
Twomethods may not have the same name and argument list but different returntypes.
134.What happens when you invoke a thread's interrupt method while it is
sleepingor waiting?
Whena task's interrupt() method is executed, the task enters the ready state. Thenext
timethe task enters
therunning state, an InterruptedException is thrown.
135.What is casting?
Thereare two types of casting, casting between primitive numeric types and casting
betweenobject
references.Casting between numeric types is used to convert larger values, such as
doublevalues, to
smallervalues, such as byte values. Casting between object references is used to referto
anobject by a
compatibleclass, interface, or array type reference.
136.What is the return type of a program's main() method?
Aprogram'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?
AChoice is displayed in a compact form that requires you to pull it down to seethe list
ofavailable
choices.Only one item may be selected from a Choice. A List may be displayed in such a
waythat several
Listitems 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?
TheJava runtime system generates RuntimeException and Error exceptions.
140.What class allows you to read objects directly from a stream?
TheObjectInputStream class supports the reading of objects from input streams.
141.What is the difference between a field variable and a local variable?
Afield variable is a variable that is declared as a member of a class. A localvariable is a
variablethat is
declaredlocal to a method.
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142.Under what conditions is an object's finalize() method invoked by the garbage
collector?
Thegarbage collector invokes an object's finalize() method when it detects thatthe object
hasbecome
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
superclassconstructor.
144.What is the relationship between a method's throws clause and the exceptions
thatcan be
thrownduring the method's execution?
Amethod's throws clause must declare any checked exceptions that are not caughtwithin
thebody of the
method.
145.What is the difference between the JDK 1.02 event model and the eventdelegation
model
introducedwith JDK 1.1?
TheJDK 1.02 event model uses an event inheritance or bubbling approach. In thismodel,
componentsare
requiredto handle their own events. If they do not handle a particular event, the eventis
inheritedby (or
bubbledup to) the component's container. The container then either handles the eventor
itis bubbled up to
itscontainer and so on, until the highest-level container has been tried.
Inthe event-delegation model, specific objects are designated as event handlersfor GUI
components.
Theseobjects implement event-listener interfaces. The event-delegation model is more
efficientthan the
event-inheritancemodel because it eliminates the processing required to support the
bubblingof unhandled
events.
146.How is it possible for two String objects with identical values not to be equal
underthe ==
operator?
The== operator compares two objects to determine if they are the same object in
memory.It is possible for
twoString objects to have the same value, but located indifferent areas of memory.
147.Why are the methods of the Math class static?
Sothey can be invoked as if they are a mathematical code library.
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148.What Checkbox method allows you to tell if a Checkbox is checked?
getState()
149.What state is a thread in when it is executing?
Anexecuting thread is in the running state.
150.What are the legal operands of the instanceof operator?
Theleft operand is an object reference or null value and the right operand is aclass,
interface,or array type.
151.How are the elements of a GridLayout organized?
Theelements of a GridBad layout are of equal size and are laid out using thesquares of a
grid.
152.What an I/O filter?
AnI/O filter is an object that reads from one stream and writes to another,usually
alteringthe data in some
wayas it is passed from one stream to another.
153.If an object is garbage collected, can it become reachable again?
Oncean object is garbage collected, it ceases to exist. It can no longer becomereachable
again.
154.What is the Set interface?
TheSet interface provides methods for accessing the elements of a finitemathematical
set.Sets do not
allowduplicate elements.
155.What classes of exceptions may be thrown by a throw statement?
Athrow statement may throw any expression that may be assigned to the Throwable
type.
156.What are E and PI?
Eis the base of the natural logarithm and PI is mathematical value pi.
157.Are true and false keywords?
Thevalues true and false are not keywords.
158.What is a void return type?
Avoid return type indicates that a method does not return a value.
159.What is the purpose of the enableEvents() method?
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TheenableEvents() method is used to enable an event for a particular object.Normally,
anevent is enabled
whena listener is added to an object for a particular event. The enableEvents()method is
usedby objects
thathandle events by overriding their event-dispatch methods.
160.What is the difference between the File and RandomAccessFile classes?
TheFile class encapsulates the files and directories of the local file system. The
RandomAccessFileclass
providesthe 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?
Theresult is a String object.
162.What is your platform's default character encoding?
Ifyou are running Java on English Windows platforms, it is probably Cp1252. Ifyou are
runningJava on
EnglishSolaris platforms, it is most likely 8859_1..
163.Which package is always imported by default?
Thejava.lang package is always imported by default.
164.What interface must an object implement before it can be written to a stream
asan object?
Anobject must implement the Serializable or Externalizable interface before itcan be
writtento a stream as
anobject.
165.How are this and super used?
thisis used to refer to the current object instance. super is used to refer to thevariables
andmethods of the
superclassof the current object instance.
166.What is the purpose of garbage collection?
Thepurpose of garbage collection is to identify and discard objects that are nolonger
neededby a program
sothat their resources may be reclaimed and reused.
167.What is a compilation unit?
Acompilation unit is a Java source code file.
168.What interface is extended by AWT event listeners?
AllAWT event listeners extend the java.util.EventListener interface.
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169.What restrictions are placed on method overriding?
Overriddenmethods must have the same name, argument list, and return type. The
overridingmethod may
notlimit the access of the method it overrides. The overriding method may notthrow
anyexceptions that
maynot be thrown by the overridden method.
170.How can a dead thread be restarted?
Adead thread cannot be restarted.
171.What happens if an exception is not caught?
Anuncaught exception results in the uncaughtException() method of the thread's
ThreadGroupbeing
invoked,which eventually results in the termination of the program in which it isthrown.
172.What is a layout manager?
Alayout manager is an object that is used to organize components in a container.
173.Which arithmetic operations can result in the throwing of an
ArithmeticException?
Integer/ and % can result in the throwing of an ArithmeticException.
174.What are three ways in which a thread can enter the waiting state?
Athread can enter the waiting state by invoking its sleep() method, by blockingon I/O,
byunsuccessfully
attemptingto acquire an object's lock, or by invoking an object's wait() method. It can
alsoenter the
waitingstate by invoking its (deprecated) suspend() method.
175.Can an abstract class be final?
Anabstract class may not be declared as final.
176.What is the ResourceBundle class?
TheResourceBundle class is used to store locale-specific resources that can beloaded by
aprogram to
tailorthe 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
handlean
exceptionthat is thrown within the body of the try statement?
Theexception propagates up to the next higher level try-catch statement (if any)or
resultsin the program's
termination.
178.What is numeric promotion?
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Numericpromotion is the conversion of a smaller numeric type to a larger numeric type,
sothat integer and
floating-pointoperations may take place. In numerical promotion, byte, char, and short
valuesare
convertedto int values. The int values are also converted to long values, if necessary.
Thelong and float
valuesare converted to double values, as required.
179.What is the difference between a Scrollbar and a ScrollPane?
AScrollbar is a Component, but not a Container. A ScrollPane is a Container. A
ScrollPanehandles its
ownevents and performs its own scrolling.
180.What is the difference between a public and a non-public class?
Apublic class may be accessed outside of its package. A non-public class may notbe
accessedoutside of
itspackage.
181.To what value is a variable of the boolean type automatically initialized?
Thedefault value of the boolean type is false.
182.Can try statements be nested?
Trystatements may be tested.
183.What is the difference between the prefix and postfix forms of the ++ operator?
Theprefix form performs the increment operation and returns the value of theincrement
operation.The
postfixform returns the current value all of the expression and then performs the
incrementoperation on
thatvalue.
184.What is the purpose of a statement block?
Astatement block is used to organize a sequence of statements as a singlestatement
group.
185.What is a Java package and how is it used?
AJava package is a naming context for classes and interfaces. A package is usedto
createa separate name
spacefor groups of classes and interfaces. Packages are also used to organizerelated
classesand interfaces
intoa single API unit and to control accessibility to these classes and interfaces.
186.What modifiers may be used with a top-level class?
Atop-level class may be public, abstract, or final.
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187.What are the Object and Class classes used for?
TheObject class is the highest-level class in the Java class hierarchy. The Classclass is
usedto represent
theclasses and interfaces that are loaded by a Java program.
188.How does a try statement determine which catch clause should be used to
handlean exception?
Whenan exception is thrown within the body of a try statement, the catch clauses ofthe
trystatement are
examinedin the order in which they appear. The first catch clause that is capable of
handlingthe exception
isexecuted. The remaining catch clauses are ignored.
189.Can an unreachable object become reachable again?
Anunreachable object may become reachable again. This can happen when theobject's
finalize()method is
invokedand the object performs an operation which causes it to become accessible to
reachableobjects.
190.When is an object subject to garbage collection?
Anobject is subject to garbage collection when it becomes unreachable to theprogram in
whichit is used.
191.What method must be implemented by all threads?
Alltasks must implement the run() method, whether they are a subclass of Thread or
implementthe
Runnableinterface.
192.What methods are used to get and set the text label displayed by a Button
object?
getLabel()and setLabel()
193.Which Component subclass is used for drawing and painting?
Canvas
194.What are synchronized methods and synchronized statements?
Synchronizedmethods are methods that are used to control access to an object. A thread
onlyexecutes a
synchronizedmethod after it has acquired the lock for the method's object or class.
Synchronized
statementsare similar to synchronized methods. A synchronized statement can only be
executedafter a
threadhas acquired the lock for the object or class referenced in the synchronized
statement.
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195.What are the two basic ways in which classes that can be run as threads may be
defined?
Athread class may be declared as a subclass of Thread, or it may implement the
Runnableinterface.
196.What are the problems faced by Java programmers who don't use layout
managers?
Withoutlayout managers, Java programmers are faced with determining how their GUI
willbe displayed
acrossmultiple windowing systems and finding a common sizing and positioning that
willwork within the
constraintsimposed by each windowing system.
197.What is the difference between an if statement and a switch statement?
Theif statement is used to select among two alternatives. It uses a booleanexpression to
decidewhich
alternativeshould be executed. The switch statement is used to select among multiple
alternatives.It uses
anint expression to determine which alternative should be executed.
198.What is the List interface?
TheList interface provides support for ordered collections of objects.
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