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If you're looking for information on Java interview questions, you've come to the right place! This guide will provide you with a comprehensive list of common Java interview questions and answers.

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#	Question	Options	Answer
1	Which of those doesn’t have an index based structure?	List Set Map Queue	Set
2	java.util.Collections is a:	Class Interface Object None of the above	Class
3	Methods such as reverse, shuffle are offered in:	Object Collection Collections Apache Commons Collections	Collections
4	Which of those allows duplicate elements?	Set List All None of the above	List
5	Which allows the storage of a null key and null values?	Hashtable HashMap Set None of the above	HashMap
6	Which interface should be implemented for sorting on basis of many criteria’s?	Comparator Comparable Serializable None of the above	Comparator
7	What guarantees type-safety in a collection?	Generics Abstract classes Interfaces Collection	Generics
8	The most used interfaces from the collection framework are?	List Map Set Queue	Map
9	The root interface of Java collection framework hierarchy is –	Collection Root Collections List/Set	List/Set
10	Which of those is synchronized?	ArrayList LinkedList Vector None of the above	Vector
11	ArrayList implements that of the following?	List RandomAccess Cloneable All of these	All of these
12	Which of those permits the storage of the many null values?	Set List None of these All of these	All of these
13	Which doesn’t permit to store a null value?	TreeSet LinkedHashSet HashSet None	TreeSet
14	TreeMap implements?	Dictionary HashMap AbstractMap Navigable Map	Navigable Map
15	Which of these standard collection classes implements a dynamic array?	LinkedList AbstractSet AbstractList ArrayList	ArrayList
16	Which of these method of ArrayList class is used to obtain present size of an object?	capacity() index() size() length()	size()
17	Which of the below does not implement Map interface?	HashMap Hashtable Vector EnumMap	Vector
18	How to externally synchronize hashmap?	HashMap.synchronize(HashMap a); Collections.synchronizedMap(new HashMap()); HashMap a = new HashMap(); Collections.synchronize(new HashMap());	Collections.synchronizedMap(new HashMap());
19	How can we remove an object from ArrayList?	remove() method and using Iterator delete() method using Iterator remove() method	remove() method and using Iterator
20	Which class provides thread safe implementation of List?	ArrayList List HashList CopyOnWriteArrayList	CopyOnWriteArrayList
21	What is the relation between hashset and hashmap?	HashMap is the interface; HashSet is the concrete class HashMap internally implements HashSet HashSet internally implements HashMap HashSet is the interface; HashMap is the concrete class	HashSet internally implements HashMap
22	Which of these object stores association between keys and values?	Map Array Hash table String	Map
23	Which of these classes provide implementation of map interface?	LinkedList ArrayList HashMap DynamicList	HashMap
24	Which of these methods can be used to obtain set of all keys in a map?	keyall() getAll() getKeys() keySet()	keySet()
25	Which of these are legacy classes?	Vector All of the mentioned Stack Hashtable	All of the mentioned
26	Which of the following is not OOPS concept in Java?	Inheritance Encapsulation Polymorphism Compilation	Compilation
27	When does method overloading is determined?	At run time At compile time At coding time At execution time	At compile time
28	When Overloading does not occur?	More than one method with same name but different method signature and different number or type of parameters. More than one method with same name, same signature but different number of signature. More than one method with same name, same signature, same number of parameters but different type More than one method with same name, same number of parameters and type but different signature	More than one method with same name, same number of parameters and type but different signature
29	Which concept of Java is a way of converting real world objects in terms of class?	Polymorphism Encapsulation Abstraction Inheritance	Abstraction
30	Which concept of Java is achieved by combining methods and attribute into a class?	Encapsulation Inheritance Polymorphism Abstraction	Encapsulation
31	What is it called where child object gets killed if parent object is killed?	Aggregation Composition Encapsulation Association	Composition
32	Which component is used to compile, debug and execute java program?	JVM JDK JIT JRE	JDK
33	Which component is responsible for converting bytecode into machine specific code?	JVM JDK JIT JRE	JVM
34	Which component is responsible to run java program?	JVM JDK JIT JRE	JRE
35	Which component is responsible to optimize bytecode to machine code?	JVM JDK JIT JRE	JIT
36	Which of the below is invalid identifier with the main method?	public static private final	private
37	What is use of interpreter?	They convert bytecode to machine language code They read high level code and execute them They are intermediated between JIT and JVM It is a synonym for JIT	They read high level code and execute them
38	Which of the following is a valid declaration of an object of class Box?	Box obj = new Box(); Box obj = new Box; obj = new Box(); new Box obj;	Box obj = new Box();
39	Which of these operators is used to allocate memory for an object?	malloc alloc new give	new
40	Which of the following statements is correct?	Public method is accessible to all other classes in the hierarchy Public method is accessible only to subclasses of its parent class Public method can only be called by object of its class Public method can be accessed by calling object of the public class	Public method is accessible to all other classes in the hierarchy
41	What is the process of defining more than one method in a class differentiated by method signature?	Method overriding Method overloading Method doubling None of the mentioned	Method overloading
42	Which of the following is a method having same name as that of it’s class?	finalize delete class constructor	constructor
43	Which method can be defined only once in a program?	main method finalize method static method private method	main method
44	Which keyword is used by the method to refer to the object that invoked it?	import catch abstract this	this
45	Which function is used to perform some action when the object is to be destroyed?	finalize() delete() main() none of the mentioned	finalize()
46	What is false about constructor?	Constructors cannot be synchronized in Java Java does not provide default copy constructor Constructor can have a return type “this” and “super” can be used in a constructor	Constructor can have a return type
47	Which of these access specifier must be used for class so that it can be inherited by another subclass?	public private protected none of the mentioned	public
48	What is the process by which we can control what parts of a program can access the members of a class?	Polymorphism Abstraction Encapsulation Recursion	Encapsulation
49	Which of these is used as default for a member of a class if no access specifier is used for it?	public public, within its own package protected private	private
50	What is use of interpreter?	They are intermediated between JIT and JVM It is a synonym for JIT They convert bytecode to machine language code They read high level code and execute them	They read high level code and execute them
51	What is the extension of compiled java classes?	.txt .class .js .java	.class
52	Which of the below is invalid identifier with main method?	private final static public	private
53	Which of these package is used for text formatting in Java programming language?	java.awt java.awt.text java.io java.text	java.text
54	Which environment variable is used to set java path?	CLASSPATH JAVA_HOME MAVEN_HOME JAVA	JAVA_HOME
55	Which of these can not be used for a variable name in Java?	identifier identifier & keyword keyword None of these	keyword
56	Literals in java must be appended by which of these?	L L and I D l	L and I
57	What is true of final class?	Final class cannot be instantiated Final class cannot be inherited Final class cause compilation failure Final class cause runtime failure	Final class cannot be inherited
58	All the variables of interface should be ?	default and static default and final protect, static and final public,static and final	public,static and final
59	How can a protected modifier be accessed?	accessible by all accessible only within package accessible only within the class accessible within package and outside the package but through inheritance only	accessible within package and outside the package but through inheritance only
60	Which of the following modifier means a particular variable cannot be accessed within the package?	protected default private public	private
61	All the variables of class should be ideally declared as ?	default private public protected	private
62	Which one of the following is not an access modifier?	Void Protected Private Public	Void
63	Which of the following is not a valid flow control statement?	continue break return exit()	exit()
64	What is true about do statement?	do statement executes the code more than once always do statement executes the code of a loop at least once do statement does not get execute if condition is not matched in the first iteration do statement checks the condition at the beginning of the loop	do statement executes the code of a loop at least once
65	Which of the following loops will execute the body of loop even when condition controlling the loop is initially false?	while for if do-while	do-while
66	Which of these method of class StringBuffer is used to find the length of current character sequence?	Length() capacity() Capacity() length()	length()
67	Which of these method of class String is used to remove leading and trailing whitespaces?	Trim() doTrim() startsWith() trim()	trim()
68	Which of this method of class String is used to extract a substring from a String object?	Substring() tostring() substring() SubString()	substring()
69	Which of these method of class String is used to compare two String objects for their equality?	Isequal() isequal() Equals() equals()	equals()
70	Which of these is an incorrect statement?	String objects are mutable, they cannot be changed StringBuffer class is used to store string in a buffer for later use String object can point to some other reference of String variable String objects are immutable, they cannot be changed	StringBuffer class is used to store string in a buffer for later use
71	Which of this method of class String is used to obtain a length of String object?	Sizeof() length() get() lengthof()	length()
72	Which of these methods can be used to search an element in a list?	get() binaryserach() sort() find()	binaryserach()
73	Which of these cannot be declared static?	variable method class object	object
74	Which of these keywords is used to prevent content of a variable from being modified?	last final constant static	final
75	Arrays in Java are implemented as?	object class variable method	object
76	Where is array stored in memory?	first generation memory stack space heap space and stack space heap space	heap space
77	Can you make an array volatile?	No Not possible True False	True
78	Which of these is an incorrect Statement?	Array can be initialized when they are declared. Array can be initialized using comma separated expressions surrounded by curly braces. It is necessary to use new operator to initialize an array. None of these	It is necessary to use new operator to initialize an array.
79	Which of these classes is super class of Exception class?	Class RunTime Throwable System	Throwable
80	Which of these methods return description of an exception?	obtainException() obtainDescription() getMessage() getException()	getMessage()
81	Which of these statements is incorrect?	try can be followed by both catch and finally block try need not to be followed by anything try block need not to be followed by catch block try block can be followed by finally block instead of catch block	try need not to be followed by anything
82	Which of these keywords are used for generating an exception manually?	check try catch throw	throw
83	Which of these keywords are used for the block to handle the exceptions generated by try block?	check throw try catch	catch
84	Which of these keywords are used for the block to be examined for exceptions?	try catch throw check	try
85	What is the use of try and catch?	It allows to fix errors It prevents automatic terminating of the program in cases when an exception occurs It allows us to manually handle the exception All of Above	All of Above
86	Which of these exceptions will occur if we try to access the index of an array beyond its length?	ArrayIndexException ArithmeticException ArrayIndexOutOfBoundsException ArrayException	ArrayIndexOutOfBoundsException
87	A single try block must be followed by which of these?	try finally catch finally & catch	finally & catch
88	Which of these clause will be executed even if no exceptions are found?	catch throw finally throws	finally
89	Which of these class is related to all the exceptions that are explicitly thrown?	Exception Throw Error Throwable	Throwable
90	Which of these keywords is used to generate an exception explicitly?	catch throw finally try	throw
91	What exception thrown by parseInt() method?	NullPointerException NumberFormatException ArithmeticException ClassNotFoundException	NumberFormatException
92	Which of these handles the exception when no catch is used?	throw handler Java run time system Default handler finally	Default handler
93	Which of these class is related to all the exceptions that cannot be caught?	Exception RuntimeExecption Error All of above	Error
94	Which part of code gets executed whether exception is caught or not?	throw try finally catch	finally
95	Which of the following keywords is used for throwing exception manually?	catch throw try finally	throw
96	What would be the result if a class extends two interfaces and both have a method with same name and signature?	Code runs successfully First called method is executed successfully Runtime error Compile time error	Compile time error
97	Which of the following is used for implementing inheritance through class?	implements inherited using extends	extends
98	Which of the following is used for implementing inheritance through an interface?	extends inherited implements using	implements
99	Static members are not inherited to subclass.	return 0 return values False True	False
100	If super class and subclass have same variable name, which keyword should be used to use super class?	this classname super upper	super
101	In order to restrict a variable of a class from inheriting to subclass, how variable should be declared?	Protected Public Static Private	Private
102	All classes in Java are inherited from which class?	java.class.object java.lang.class java.lang.Object java.class.inherited	java.lang.Object
103	Using which of the following, multiple inheritance in Java can be implemented?	Multithreading Private methods Interfaces Protected methods	Interfaces
104	Which of this keyword must be used to inherit a class?	extends extent this super	extends
105	Which of these is supported by method overriding in Java?	class Polymorphism Encapsulation Abstraction	Polymorphism
106	If a class inheriting an abstract class does not define all of its function then it will be known as?	A simple class interface Abstract Static class	Abstract
107	Which of these is not abstract?	Queue List AbstractList Thread	Thread
108	Which of this package is used for handling security related issues in a program?	java.lang.security java.awt.image java.security java.io.security	java.security
109	Which of these methods can randomize all elements in a list?	randomize() rand() ambiguous() shuffle()	shuffle()
110	Which of these must contain a unique element?	List Set Collection Array	Set
111	Which of these interface handle sequences?	Collection Comparator List Set	List
112	Which of these is a method of ListIterator used to obtain index of previous element?	back() previous() goBack() previousIndex()	previousIndex()
113	Which of these methods can be used to move to next element in a collection?	hasNext() shuffle() move() next()	next()
114	Which of these return type of hasNext() method of an iterator?	Boolean Double Integer Collections Object	Boolean
115	What is Collection in Java?	A group of classes A group of interfaces A group of objects All of above	A group of objects
116	Which of these methods deletes all the elements from invoking collection?	refresh() delete() reset() clear()	clear()
117	Which of these classes is not part of Java’s collection framework?	Stack Queue Array Maps	Maps
118	Which of these packages contain all the collection classes?	java.net java.lang java.util java.awt	java.util
119	Which of these methods is used to retrieve the elements in properties object at specific location?	ElementAt() get() getProperty() Elementat()	getProperty()
120	Which of these method is used to insert value and its key?	addElement() insertElement() put() set()	put()
121	Which of these class object uses the key to store value?	Hashtable Dictionary Map All of above	All of above
122	Which of these methods is used to add elements in vector at specific location?	set() add() addElement() AddElement()	addElement()
123	Which of these are legacy classes?	Vector Stack Hashtable All of Above	All of Above
124	Which of these methods can be used to obtain set of all keys in a map?	keyall() keySet() getAll() getKeys()	keySet()
125	Which of these method is used to remove all keys/values pair from the invoking map?	removeAll() clear() remove() delete()	remove()
126	Which of the following is not OOPS concept in Java?	Inheritance Encapsulation Polymorphism Compilation	Compilation
127	Which of the following is a type of polymorphism in Java?	Compile time polymorphism Execution time polymorphism Multiple polymorphism Multilevel polymorphism	Compile time polymorphism
128	When does method overloading is determined?	At run time At compile time At coding time At execution time	At compile time
129	When Overloading does not occur?	More than one method with same name but different method signature and different number or type of parameters More than one method with same name, same signature but different number of signature More than one method with same name, same signature, same number of parameters but different type More than one method with same name, same number of parameters and type but different signature	More than one method with same name, same number of parameters and type but different signature
130	Which concept of Java is a way of converting real world objects in terms of class?	Polymorphism Encapsulation Abstraction Inheritance	Abstraction
131	Which concept of Java is achieved by combining methods and attribute into a class?	Encapsulation Inheritance Polymorphism Abstraction	Encapsulation
132	What is it called if an object has its own lifecycle and there is no owner?	Aggregation Composition Encapsulation Association	Association
133	What is it called where child object gets killed if parent object is killed?	Aggregation Composition Encapsulation Association	Composition
134	What is it called where object has its own lifecycle and child object cannot belong to another parent object?	Aggregation Composition Encapsulation Association	Aggregation
135	Method overriding is combination of inheritance and polymorphism?	True False None All of the above	True
136	What is the stored in the object obj in following lines of Java code? -> box obj;	Memory address of allocated memory of object NULL Any arbitrary pointer Garbage	NULL
137	Which of these keywords is used to make a class?	class struct int none of the mentioned	class
138	Which of the following is a valid declaration of an object of class Box?	Box obj = new Box(); Box obj = new Box; obj = new Box(); new Box obj;	Box obj = new Box();
139	Which of these statement is incorrect?	Every class must contain a main() method Applets do not require a main() method at all There can be only one main() method in a program main() method must be made public	Every class must contain a main() method
140	Which of the following statements is correct?	Public method is accessible to all other classes in the hierarchy Public method is accessible only to subclasses of its parent class Public method can only be called by object of its class Public method can be accessed by calling object of the public class	Public method is accessible to all other classes in the hierarchy
141	What is the return type of a method that does not return any value?	int float void double	void
142	Which of the following is a method having same name as that of it’s class?	finalize delete class constructor	constructor
143	Which method can be defined only once in a program?	main method finalize method static method private method	main method
144	Which of this statement is incorrect?	All object of a class are allotted memory for the all the variables defined in the class If a function is defined public it can be accessed by object of other class by inheritance main() method must be made public All object of a class are allotted memory for the methods defined in the class	All object of a class are allotted memory for the methods defined in the class
145	What is the return type of Constructors?	int float void none of the mentioned	none of the mentioned
146	Which keyword is used by the method to refer to the object that invoked it?	import catch abstract this	this
147	Which operator is used by Java run time implementations to free the memory of an object when it is no longer needed?	delete free new none of the mentioned	none of the mentioned
148	Which function is used to perform some action when the object is to be destroyed?	finalize() delete() main() none of the mentioned	finalize()
149	Which of the following statements are incorrect?	default constructor is called at the time of object declaration constructor can be parameterized finalize() method is called when a object goes out of scope and is no longer needed finalize() method must be declared protected	finalize() method is called when a object goes out of scope and is no longer needed
150	What is true about private constructor?	Private constructor ensures only one instance of a class exist at any point of time Private constructor ensures multiple instances of a class exist at any point of time Private constructor eases the instantiation of a class Private constructor allows creating objects in other classes	Private constructor ensures only one instance of a class exist at any point of time
151	What would be the behaviour if this() and super() used in a method?	Runtime error Throws exception compile time error Runs successfully	compile time error
152	What is false about constructor?	Constructors cannot be synchronized in Java Java does not provide default copy constructor Constructor can have a return type this and super can be used in a constructor	Constructor can have a return type
153	What is true about Class.getInstance()?	Class.getInstance calls the constructor Class.getInstance is same as new operator Class.getInstance needs to have matching constructor Class.getInstance creates object if class does not have any constructor	Class.getInstance creates object if class does not have any constructor
154	What is true about protected constructor?	Protected constructor can be called directly Protected constructor can only be called using super() Protected constructor can be used outside package protected constructor can be instantiated even if child is in a different package	Protected constructor can only be called using super()
155	What is not the use of this keyword in Java?	Passing itself to another method Calling another constructor in constructor chaining Referring to the instance variable when local variable has the same name Passing itself to method of the same class	Passing itself to method of the same class
156	What would be the behaviour if one parameterized constructor is explicitly defined?	Compilation error Compilation succeeds Runtime error Compilation succeeds but at the time of creating object using default constructor, it throws compilation error	Compilation succeeds but at the time of creating object using default constructor, it throws compilation error
157	What would be behaviour if the constructor has a return type?	Compilation error Runtime error Compilation and runs successfully Only String return type is allowed	Compilation error
158	What is the process of defining two or more methods within same class that have same name but different parameters declaration?	method overloading method overriding method hiding none of the mentioned	method overloading
159	Which of these can be overloaded?	Methods Constructors All of the mentioned None of the mentioned	All of the mentioned
160	Which of these is correct about passing an argument by call-by-value process?	Copy of argument is made into the formal parameter of the subroutine Reference to original argument is passed to formal parameter of the subroutine Copy of argument is made into the formal parameter of the subroutine and changes made on parameters of subroutine have effect on original argument Reference to original argument is passed to formal parameter of the subroutine and changes made on parameters of subroutine have effect on original argument	Copy of argument is made into the formal parameter of the subroutine
161	What is the process of defining a method in terms of itself, that is a method that calls itself?	Polymorphism Abstraction Encapsulation Recursion	Recursion
162	Which of these access specifiers must be used for main() method?	private public protected none of the mentioned	public
163	Which of these is used to access a member of class before object of that class is created?	public private static protected	static
164	Which of these is used as a default for a member of a class if no access specifier is used for it?	private public public, within its own package protected	private
165	What is the process by which we can control what parts of a program can access the members of a class?	Polymorphism Abstraction Encapsulation Recursion	Encapsulation
166	Which of the following statements are incorrect?	public members of class can be accessed by any code in the program private members of class can only be accessed by other members of the class private members of class can be inherited by a subclass, and become protected members in subclass protected members of a class can be inherited by a subclass, and become private members of the subclass	private members of class can be inherited by a subclass, and become protected members in subclass
167	Which of these access specifier must be used for class so that it can be inherited by another subclass?	public private protected none of the mentioned	public
168	Which one of the following is not an access modifier?	Public Private Protected Void	Void
169	All the variables of class should be ideally declared as?	private public protected default	private
170	Which of the following modifier means a particular variable cannot be accessed within the package?	private public protected default	private
171	How can a protected modifier be accessed?	accessible only within the class accessible only within package accessible within package and outside the package but through inheritance only accessible by all	accessible within package and outside the package but through inheritance only
172	What happens if constructor of class A is made private?	Any class can instantiate objects of class A Objects of class A can be instantiated only within the class where it is declared Inherited class can instantiate objects of class A classes within the same package as class A can instantiate objects of class A	Objects of class A can be instantiated only within the class where it is declared
173	All the variables of interface should be?	default and final default and static public, static and final protect, static and final	public, static and final
174	What is true of final class?	Final class cause compilation failure Final class cannot be instantiated Final class cause runtime failure Final class cannot be inherited	Final class cannot be inherited
175	How many copies of static and class variables are created when 10 objects are created of a class?	1, 10 10, 10 10, 1 1, 1	1, 10
176	Which is the modifier when there is none mentioned explicitly?	protected private public default	default
177	String in Java is a?	class object variable character array	class
178	Which of these method of String class is used to obtain character at specified index?	char() Charat() charat() charAt()	charAt()
179	Which of these keywords is used to refer to member of base class from a subclass?	upper super this none of the mentioned	super
180	Which of these method of String class can be used to test to strings for equality?	isequal() isequals() equal() equals()	equals()
181	Which of the following statements are incorrect?	String is a class Strings in java are mutable Every string is an object of class String Java defines a peer class of String, called StringBuffer, which allows string to be altered	Strings in java are mutable
182	Which of this keyword can be used in a subclass to call the constructor of superclass?	super this extent extends	super
183	What is the process of defining a method in a subclass having same name & type signature as a method in its superclass?	Method overloading Method overriding Method hiding None of the mentioned	Method overriding
184	Which of these keywords can be used to prevent Method overriding?	static constant protected final	final
185	Which of these is supported by method overriding in Java?	Abstraction Encapsulation Polymorphism None of the mentioned	Polymorphism
186	What is not type of inheritance?	Single inheritance Double inheritance Hierarchical inheritance Multiple inheritance	Double inheritance
187	Using which of the following, multiple inheritance in Java can be implemented?	Interfaces Multithreading Protected methods Private methods	Interfaces
188	All classes in Java are inherited from which class?	java.lang.class java.class.inherited java.class.object java.lang.Object	java.lang.Object
189	In order to restrict a variable of a class from inheriting to subclass, how variable should be declared?	Protected Private Public Static	Private
190	If super class and subclass have same variable name, which keyword should be used to use super class?	super this upper classname	super
191	Static members are not inherited to subclass.	True False Not Sure None	True
192	Which of the following is used for implementing inheritance through an interface?	inherited using extends implements	implements
193	Which of the following is used for implementing inheritance through class?	inherited using extends implements	extends
194	What would be the result if a class extends two interfaces and both have a method with same name and signature? Lets assume that the class is not implementing that method.	Runtime error Compile time error Code runs successfully First called method is executed successfully	Compile time error
195	Which of these class is superclass of every class in Java?	String class Object class Abstract class ArrayList class	Object class
196	Which of these method of Object class can clone an object?	Objectcopy() copy() Object clone() clone()	Object clone()
197	Which of these method of Object class is used to obtain class of an object at run time?	get() void getclass() Class getclass() None of the mentioned	Class getclass()
198	Which of these keywords can be used to prevent inheritance of a class?	super constant class final	final
199	Which of these keywords cannot be used for a class which has been declared final?	abstract extends abstract and extends none of the mentioned	abstract
200	Which of these class relies upon its subclasses for complete implementation of its methods?	Object class abstract class ArrayList class None of the mentioned	abstract class
201	Which of these keywords are used to define an abstract class?	abst abstract Abstract abstract class	abstract
202	Which of these is not abstract?	Thread AbstractList List None of the Mentioned	Thread
203	If a class inheriting an abstract class does not define all of its function then it will be known as?	Abstract A simple class Static class None of the mentioned	Abstract
204	Which of these is not a correct statement?	Every class containing abstract method must be declared abstract Abstract class defines only the structure of the class not its implementation Abstract class can be initiated by new operator Abstract class can be inherited	Abstract class can be initiated by new operator
205	Which of these packages contains abstract keyword?	java.lang java.util java.io java.system	java.lang
206	Which of these class is superclass of String and StringBuffer class?	java.util java.lang ArrayList None of the mentioned	java.lang
207	Which of these operators can be used to concatenate two or more String objects?	+ += & ||	+
208	Which of this method of class String is used to obtain a length of String object?	get() Sizeof() lengthof() length()	length()
209	Which of these constructors is used to create an empty String object?	String() String(void) String(0) None of the mentioned	String()
210	Which of these is an incorrect statement?	String objects are immutable, they cannot be changed String object can point to some other reference of String variable StringBuffer class is used to store string in a buffer for later use None of the mentioned	StringBuffer class is used to store string in a buffer for later use
211	Which of this method of class String is used to extract a substring from a String object?	substring() Substring() SubString() None of the mentioned	substring()
212	Which of these method of class String is used to remove leading and trailing whitespaces?	startsWith() trim() Trim() doTrim()	trim()
213	What is the value returned by function compareTo() if the invoking string is greater than the string compared?	zero value less than zero value greater than zero none of the mentioned	value greater than zero
214	Which of the following statement is correct?	replace() method replaces all occurrences of one character in invoking string with another character replace() method replaces only first occurrences of a character in invoking string with another character replace() method replaces all the characters in invoking string with another character replace() replace() method replaces last occurrence of a character in invoking string with another character	replace() method replaces all occurrences of one character in invoking string with another character
215	Which of these method of class String is used to compare two String objects for their equality?	equals() Equals() isequal() Isequal()	equals()
216	Which of these methods is used to compare a specific region inside a string with another specific region in another string?	regionMatch() match() RegionMatches() regionMatches()	regionMatches()
217	Which of these methods of class String is used to check whether a given object starts with a particular string literal?	startsWith() endsWith() Starts() ends()	startsWith()
218	What is the value returned by function compareTo() if the invoking string is less than the string compared?	zero value less than zero value greater than zero none of the mentioned	value less than zero
219	Which of these data type value is returned by equals() method of String class?	char int boolean all of the mentioned	boolean
220	Which of these class is used to create an object whose character sequence is mutable?	String() StringBuffer() String() & StringBuffer() None of the mentioned	StringBuffer()
221	Which of this method of class StringBuffer is used to concatenate the string representation to the end of invoking string?	concat() append() join() concatenate()	append()
222	Which of these method of class StringBuffer is used to find the length of current character sequence?	length() Length() capacity() Capacity()	length()
223	Which of the following statement is correct?	reverse() method reverses all characters reverseall() method reverses all characters replace() method replaces first occurrence of a character in invoking string with another character replace() method replaces last occurrence of a character in invoking string with another character	reverse() method reverses all characters
224	Which of these methods of class StringBuffer is used to extract a substring from a String object?	substring() Substring() SubString() None of the mentioned	substring()
225	Which of this method of class StringBuffer is used to reverse sequence of characters?	reverse() reverseall() Reverse() reverseAll()	reverse()
226	Which of this method of class StringBuffer is used to get the length of the sequence of characters?	length() capacity() Length() Capacity()	length()
227	Which of these is a process of writing the state of an object to a byte stream?	Serialization Externalization File Filtering All of the mentioned	Serialization
228	Which of these process occur automatically by the java runtime system?	Serialization Garbage collection File Filtering All of the mentioned	Serialization
229	Which of these is an interface for control over serialization and deserialization?	Serializable Externalization FileFilter ObjectInput	Externalization
230	Which of these interface extends DataOutput interface?	Serializable Externalization ObjectOutput ObjectInput	ObjectOutput
231	Which of these is a method of ObjectOutput interface used to finalize the output state so that any buffers are cleared?	clear() flush() fflush() close()	flush()
232	Which of these is method of ObjectOutput interface used to write the object to input or output stream as required?	write() Write() StreamWrite() writeObject()	writeObject()
233	Which of these is a process of extracting/removing the state of an object from a stream?	Serialization Externalization File Filtering Deserialization	Deserialization
234	Which of these process occur automatically by java run time system?	Serialization Memory allocation Deserialization All of the mentioned	All of the mentioned
235	Which of these interface extends DataInput interface?	Serializable Externalization ObjectOutput ObjectInput	ObjectInput
236	Which of these class extend InputStream class?	ObjectStream ObjectInputStream ObjectOutput ObjectInput	ObjectInputStream
237	How an object can become serializable?	If a class implements java.io.Serializable class If a class or any superclass implements java.io.Serializable interface Any object is serializable No object is serializable	If a class or any superclass implements java.io.Serializable interface
238	What is serialization?	Turning object in memory into stream of bytes Turning stream of bytes into an object in memory Turning object in memory into stream of bits Turning stream of bits into an object in memory	Turning object in memory into stream of bytes
239	What is deserialization?	Turning object in memory into stream of bytes Turning stream of bytes into an object in memory Turning object in memory into stream of bits Turning stream of bits into an object in memory	Turning stream of bytes into an object in memory
240	How many methods Serializable has?	1 2 3 0	0
241	What type of members are not serialized?	Private Protected Static Throwable	Static
242	If member does not implement serialization, which exception would be thrown?	RuntimeException SerializableException NotSerializableException UnSerializedException	NotSerializableException
243	Which of the following methods is used to avoid serialization of new class whose super class already implements Serialization?	writeObject() readWriteObject() writeReadObject() unSerializaedObject()	writeObject()
244	Which of the following methods is not used while Serialization and DeSerialization?	readObject() readExternal() readWriteObject() writeObject()	readWriteObject()
245	Which of these package contains classes and interfaces for networking?	java.io java.util java.net java.network	java.net
246	Which of these is a protocol for breaking and sending packets to an address across a network?	TCP/IP DNS Socket Proxy Server	TCP/IP
247	How many ports of TCP/IP are reserved for specific protocols?	10 1024 2048 512	1024
248	How many bits are in a single IP address?	8 16 32 64	32
249	Which of these is a full form of DNS?	Data Network Service Data Name Service Domain Network Service Domain Name Service	Domain Name Service
250	Which of these class is used to encapsulate IP address and DNS?	DatagramPacket URL InetAddress ContentHandler	InetAddress
251	Which of these interface abstractes the output of messages from httpd?	LogMessage LogResponse Httpdserver httpdResponse	LogMessage
252	Which of these class is used to create servers that listen for either local or remote client programs?	httpServer ServerSockets MimeHeader HttpResponse	ServerSockets
253	Which of these is a standard for communicating multimedia content over email?	http https Mime httpd	Mime
254	Which of these methods is used to make raw MIME formatted string?	parse() toString() getString() parseString()	parse()
255	Which of these class is used for operating on request from the client to the server?	http httpDecoder httpConnection httpd	httpd
256	Which of these method of MimeHeader is used to return the string equivalent of the values stores on MimeHeader?	string() toString() convertString() getString()	toString()
257	Which of these is an instance variable of class httpd?	port cache log All of the mentioned	All of the mentioned
258	Which of these methods of httpd class is used to read data from the stream?	getDta() GetResponse() getStream() getRawRequest()	getRawRequest()
259	Which of these method of httpd class is used to get report on each hit to HTTP server?	log() logEntry() logHttpd() logResponse()	logEntry()
260	Which of these methods are used to find a URL from the cache of httpd?	findfromCache() findFromCache() serveFromCache() getFromCache()	serveFromCache()
261	Which of these variables stores the number of hits that are successfully served out of cache?	hits hitstocache hits_to_cache hits.to.cache	hits.to.cache
262	Which of these method of httpd class is used to write UrlCacheEntry object into local disk?	writeDiskCache() writetoDisk() writeCache() writeDiskEntry()	writeDiskCache()
263	Which of these method is used to start a server thread?	run() start() runThread() startThread()	run()
264	Which of these method is called when http daemon is acting like a normal web server?	Handle() HandleGet() handleGet() Handleget()	handleGet()
265	Which of these standard collection classes implements a dynamic array?	AbstractList LinkedList ArrayList AbstractSet	ArrayList
266	Which of these class can generate an array which can increase and decrease in size automatically?	ArrayList() DynamicList() LinkedList() MallocList()	ArrayList()
267	Which of these method of ArrayList class is used to obtain present size of an object?	size() length() index() capacity()	size()
268	Which of these methods can be used to obtain a static array from an ArrayList object?	Array() convertArray() toArray() convertoArray()	toArray()
269	Which of these method is used to reduce the capacity of an ArrayList object?	trim() trimSize() trimTosize() trimToSize()	trimToSize()
270	Map implements collection interface?	True False No idea All of the above	False
271	Which of the below does not implement Map interface?	HashMap Hashtable EnumMap Vector	Vector
272	What is the premise of equality for IdentityHashMap?	Reference equality Name equality Hashcode equality Length equality	Reference equality
273	What happens if we put a key object in a HashMap which exists?	The new object replaces the older object The new object is discarded The old object is removed from the map It throws an exception as the key already exists in the map	The new object replaces the older object
274	If two threads access the same hashmap at the same time, what would happen?	ConcurrentModificationException NullPointerException ClassNotFoundException RuntimeException	ConcurrentModificationException
275	If large number of items are stored in hash bucket, what happens to the internal structure?	The bucket will switch from LinkedList to BalancedTree The bucket will increase its size by a factor of load size defined The LinkedList will be replaced by another hashmap Any further addition throws Overflow exception	The bucket will switch from LinkedList to BalancedTree
276	How can we remove an object from ArrayList?	remove() method using Iterator remove() method and using Iterator delete() method	remove() method and using Iterator
277	How to sort elements of ArrayList?	Collection.sort(listObj); Collections.sort(listObj); listObj.sort(); Sorter.sortAsc(listObj);	Collections.sort(listObj);
278	When two threads access the same ArrayList object what is the outcome of the program?	Both are able to access the object ConcurrentModificationException is thrown One thread is able to access the object and second thread gets Null Pointer exception One thread is able to access the object and second thread will wait till control is passed to the second one	ConcurrentModificationException is thrown
279	How is Arrays.asList() different than the standard way of initialising List?	Both are same Arrays.asList() throws compilation error Arrays.asList() returns a fixed length list and doesn’t allow to add or remove elements We cannot access the list returned using Arrays.asList()	Arrays.asList() returns a fixed length list and doesn’t allow to add or remove elements
280	What is the difference between length() and size() of ArrayList?	length() and size() return the same value length() is not defined in ArrayList size() is not defined in ArrayList length() returns the capacity of ArrayList and size() returns the actual number of elements stored in the list	length() returns the capacity of ArrayList and size() returns the actual number of elements stored in the list
281	Which class provides thread safe implementation of List?	ArrayList CopyOnWriteArrayList HashList List	CopyOnWriteArrayList
282	Which of the below is not an implementation of List interface?	RoleUnresolvedList Stack AttibuteList SessionList	SessionList
283	What does Collections.emptySet() return?	Immutable Set Mutable Set The type of Set depends on the parameter passed to the emptySet() method Null object	Immutable Set
284	What is the relation between hashset and hashmap?	HashSet internally implements HashMap HashMap internally implements HashSet HashMap is the interface; HashSet is the concrete class HashSet is the interface; HashMap is the concrete class	HashSet internally implements HashMap
285	What is the difference between TreeSet and SortedSet?	TreeSet is more efficient than SortedSet SortedSet is more efficient than TreeSet TreeSet is an interface; SortedSet is a concrete class SortedSet is an interface; TreeSet is a concrete class	SortedSet is an interface; TreeSet is a concrete class
286	What happens if two threads simultaneously modify TreeSet?	ConcurrentModificationException is thrown Both threads can perform action successfully FailFastException is thrown IteratorModificationException is thrown	ConcurrentModificationException is thrown
287	What is the unique feature of LinkedHashSet?	It is not a valid class It maintains the insertion order and guarantees uniqueness It provides a way to store key values with uniqueness The elements in the collection are linked to each other	It maintains the insertion order and guarantees uniqueness
288	Which of these standard collection classes implements a linked list data structure?	AbstractList LinkedList HashSet AbstractSet	LinkedList
289	Which of these classes implements Set interface?	ArrayList HashSet LinkedList DynamicList	HashSet
290	Which of these method is used to add an element to the start of a LinkedList object?	add() first() AddFirst() addFirst()	addFirst()
291	Which of these method of HashSet class is used to add elements to its object?	add() Add() addFirst() insert()	add()
292	Which of these methods can be used to delete the last element in a LinkedList object?	remove() delete() removeLast() deleteLast()	removeLast()
293	Which of this method is used to change an element in a LinkedList Object?	change() set() redo() add()	set()
294	Which of these object stores association between keys and values?	Hash table Map Array String	Map
295	Which of these classes provide implementation of map interface?	ArrayList HashMap LinkedList DynamicList	HashMap
296	Which of these method is used to remove all keys/values pair from the invoking map?	delete() remove() clear() removeAll()	remove()
297	Which of these method Map class is used to obtain an element in the map having specified key?	search() get() set() look()	get()
298	Which of these methods can be used to obtain set of all keys in a map?	getAll() getKeys() keyall() keySet()	keySet()
299	Which of these method is used add an element and corresponding key to a map?	put() set() redo() add()	put()
300	Which of these class object can be used to form a dynamic array?	ArrayList Map Vector ArrayList & Vector	ArrayList & Vector
301	Which of these are legacy classes?	Stack Hashtable Vector All of the mentioned	All of the mentioned
302	Which of these is the interface of legacy?	Map Enumeration HashMap Hashtable	Enumeration
303	What is the name of a data member of class Vector which is used to store a number of elements in the vector?	length elements elementCount capacity	elementCount
304	Which of these methods is used to add elements in vector at specific location?	add() set() AddElement() addElement()	addElement()
305	Which of these class object has an architecture similar to that of array?	Bitset Map Hashtable All of the mentioned	Bitset
306	Which of these method is used to make a bit zero specified by the index?	put() set() remove() clear()	clear()
307	Which of these method is used to calculate number of bits required to hold the BitSet object?	size() length() indexes() numberofBits()	length()
308	Which of these packages contain all the collection classes?	java.lang java.util java.net java.awt	java.util
309	Which of these classes is not part of Java’s collection framework?	Maps Array Stack Queue	Maps
310	Which of this interface is not a part of Java’s collection framework?	List Set SortedMap SortedList	SortedList
311	Which of these methods deletes all the elements from invoking collection?	clear() reset() delete() refresh()	clear()
312	What is Collection in Java?	A group of objects A group of classes A group of interfaces None of the mentioned	A group of objects
313	Which of these return type of hasNext() method of an iterator?	Integer Double Boolean Collections Object	Boolean
314	Which of these methods is used to obtain an iterator to the start of collection?	start() begin() iteratorSet() iterator()	iterator()
315	Which of these methods can be used to move to next element in a collection?	next() move() shuffle() hasNext()	next()
316	Which of these iterators can be used only with List?	Setiterator ListIterator Literator None of the mentioned	ListIterator
317	Which of these is a method of ListIterator used to obtain index of previous element?	previous() previousIndex() back() goBack()	previousIndex()
318	Which of these exceptions is thrown by remover() method?	IOException SystemException ObjectNotFoundExeception IllegalStateException	IllegalStateException
319	When does Exceptions in Java arises in code sequence?	Run Time Compilation Time Can Occur Any Time None of the mentioned	Run Time
320	Which of these keywords is not a part of exception handling?	try finally thrown catch	thrown
321	Which of these keywords must be used to monitor for exceptions?	try finally throw catch	try
322	Which of these keywords must be used to handle the exception thrown by try block in some rational manner?	try finally throw catch	catch
323	Which of these keywords is used to manually throw an exception?	try finally throw catch	throw
324	Which of the following keywords is used for throwing exception manually?	finally try throw catch	throw
325	Which of the following classes can catch all exceptions which cannot be caught?	RuntimeException Error Exception ParentException	Error
326	Which of the following is a super class of all exception type classes?	Catchable RuntimeExceptions String Throwable	Throwable
327	Which of the following operators is used to generate instance of an exception which can be thrown using throw?	thrown alloc malloc new	new
328	Which of the following keyword is used by calling function to handle exception thrown by called function?	throws throw try catch	throws
329	Which of the following handles the exception when a catch is not used?	finally throw handler default handler java run time system	default handler
330	Which part of code gets executed whether exception is caught or not?	finally try catch throw	finally
331	Which of the following should be true of the object thrown by a thrown statement?	Should be assignable to String type Should be assignable to Exception type Should be assignable to Throwable type Should be assignable to Error type	Should be assignable to Throwable type
332	Which of these is a super class of all exceptional type classes?	String RuntimeExceptions Throwable Cacheable	Throwable
333	Which of these class is related to all the exceptions that can be caught by using catch?	Error Exception Runtime Exception All of the mentioned	Exception
334	Which of these class is related to all the exceptions that cannot be caught?	Error Exception RuntimeExecption All of the mentioned	Error
335	Which of these handles the exception when no catch is used?	Default handler finally throw handler Java run time system	Default handler
336	What exception thrown by parseInt() method?	ArithmeticException ClassNotFoundException NullPointerException NumberFormatException	NumberFormatException
337	Which of these keywords is used to generate an exception explicitly?	try finally throw catch	throw
338	Which of these class is related to all the exceptions that are explicitly thrown?	Error Exception Throwable Throw	Throwable
339	Which of these operator is used to generate an instance of an exception than can be thrown by using throw?	new malloc alloc thrown	new
340	Which of these keywords is used to by the calling function to guard against the exception that is thrown by called function?	try throw throws catch	throws
341	Which of these clause will be executed even if no exceptions are found?	throws finally throw catch	finally
342	A single try block must be followed by which of these?	finally catch finally & catch none of the mentioned	finally & catch
343	Which of these exceptions handles the divide by zero error?	Arithmetic Exception Math Exception Illegal Access Exception illegal Exception	Arithmetic Exception
344	Which of these exceptions will occur if we try to access the index of an array beyond its length?	ArithmeticException ArrayException ArrayIndexException ArrayIndexOutOfBoundsException	ArrayIndexOutOfBoundsException
345	Which of these classes is used to define exceptions?	Exception Throwable Abstract System	Exception
346	Which of these methods return description of an exception?	getException() getMessage() obtainDescription() obtainException()	getMessage()
347	What is the use of try & catch?	It allows us to manually handle the exception It allows to fix errors It prevents automatic terminating of the program in cases when an exception occurs All of the mentioned	All of the mentioned
348	Which of these keywords are used for generating an exception manually?	try catch throw check	throw
349	Which of these statements is incorrect?	try block need not to be followed by catch block try block can be followed by finally block instead of catch block try can be followed by both catch and finally block try need not to be followed by anything	try need not to be followed by anything

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