Interview Questions and Answers for 'Java' | Search Interview Question

Interview Questions and Answers - Order By Newest

Q1041. what is the use of Null is Java ?

Ans. whenever a reference is created in Java without assigning the object

like

String str;

It get's assigned to null. So null provides a temporary memory location which any reference can point to till an appropriate object is assigned. Moreover it denotes that nothing has been assigned yet and hence provides a check in many cases.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve null}

Q1042. Does assigning null and assigning empty object same in Java ?

Core Java

Ans. Null means nothing and hence means it's being assigned something till anything can be assigned to the reference. Null is a common memory location that get's assigned to any object reference till an actual object is assigned.

Empty object may not have a programmer initialized state but still a separate object in memory that has been assigned the placeholders.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve null}

Q1043. Doesn't it make sense to necessarily initialize references to some object to avoid NullPointerExceptions ? Can this be done ?

Core Java

Ans. We can declare the reference as final to avoid reassignment but again we can always initialize the final reference to null. Even if there was any such facility available , it would have meant poor use of resources by assigning a new object in memory to each reference that's created. Many a times references are just meant to refer to other objects which already have a reference i.e sharing object by multiple references.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve null NullPointerException}

Q1044. Can an object be assigned to multiple references ?

Core Java

Ans. Yes we can assign an object to multiple references like following

String str1 = new String("Hello World");
String str2 = str1;

Now both str1 and str2 points to "Hello World" in memory.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve}

Q1045. What does 'canonical representation' in Java mean ?

Core Java

^{This question is still unanswered. Can you please provide an answer.}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve}

Q1046. Can a constructor have a private access specifier ?

Core Java

Ans. Yes, declaring a constructor private means disabling the creation of object that way using new operator.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve constructor private constructor}

Q1047. Difference between int and short data types ?

Core Java

Ans. Both holds numeric values. short is a 16-bit signed two's complement integer whereas int is a 32-bit signed two's complement integer.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve data types short vs int}

Q1048. Does Java allows inter thread communication ?

Core Java

Ans. Yes. Using wait and notify methods.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve}

Q1049. What is a gobbler class ?

Core Java

Ans. A gobbler class take care of reading from a stream and optionally write out to another stream. Allows for non blocking reads when invoking a process through Runtime.exec(). Moreover the user can specify a callback that is called whenever anything is read from the stream.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve gobbler stream}

Q1050. Why do we need Garbage collection ?

Core Java

Ans. Garbage collection mechanism frees up the memory that is no longer needed. In languages like C / C++ the deallocation needs to be done explicitly by the programmer and hence any leniency may result in memory leak. Garbage collection in java ensures that all unused memory is reclaimed and hence there are no memory leaks.Moreover it relieves the programmer from the hassle of carefully releasing all memory.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Garbage Collection memory management Asked in 2 Companies}

Q1051. Is array an object in Java ? How can you prove that ?

Core Java

Ans. Yes.

There are 2 ways this can be confirmed

1. Accessing object class methods using array reference.

2. Checking if the array is an instance of Object class

if (arrayRef instanceof Object)

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve arrays}

Q1052. What was the need of creating an abstract class in Java when we cannot instantiate an object of it ?

Core Java

Ans. The objective of an abstract class is to provide an interface as well as code reuse. Though we cannot instantiate an instance of abstract class but we can reuse the code by extending such a class. Moreover abstract class provides interfacing to outside components just like interfaces.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve abstract class}

Q1053. If we don't provide any argument to the executed program, What arguments will be passed to the main method ? Will the String array argument be null ?

Core Java

Ans. No. It won't be null but an empty array with size 0

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve main method}

Q1054. What will we get if we try to print local variable that hasn't been initialized ?

Core Java

Ans. It will print the garbage value as compiler doesn't provide a default value to local variables.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve local variable default values basic}

Q1055. What is the use of constructors in Java ?

Core Java

Ans. Constructors are used to initialize the state of an object. If there are no constructor , objects won't have any initialized state and hence it's elements may contain garbage values. If the memory were used as is, the behavior of the object would also be unpredictable.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve constructor Asked in 5 Companies}

Q1056. What is synchronization ?

Core Java

^{This question was recently asked at 'ABS'.This question is still unanswered. Can you please provide an answer.}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Asked in 1 Companies}

Q1057. What is JVM ?

Core Java

Ans. JVM (Java Virtual Machine) is an abstract machine. It is a specification that provides runtime environment in which java bytecode can be executed.JVMs are available for many hardware and software platforms (i.e. JVM is platform dependent).Runtime Instance Whenever you write java command on the command prompt to run the java class, an instance of JVM is createdThe JVM performs following operation:Loads codeVerifies codeExecutes codeProvides runtime environment

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve memory management jvm Asked in 3 Companies basic frequent}

Q1058. What are the counter controlled repetitions in java ?

Core Java

Ans. Counter controlled repetitions are the loops that are controlled with the use of counters or the loops where the number of repetitions are known in advance. for loop in java is the counter controlled repetition.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve for loop control statements loop statement}

Q1059. What is recursion in Java ?

Core Java

Ans. It's a programming technique wherein the method can call itself. The method call usually involves a different set of parameters as otherwise it would lead to an infinite loop. There is usually a termination check and statement to finally return the control out of all function calls.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Asked in 1 Companies Basic}

Q1060. What will happen if we don't have termination statement in recursion ?

Core Java

Ans. It would result in endless function calls and hence eventually would result in stackoverflow exception.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve recursion stackoverflowexception Basic frequent}

Q1061. Explain OOPS.

Core Java

^{This question was recently asked at 'Acute Informatics,General Atomics'.This question is still unanswered. Can you please provide an answer.}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Asked in 2 Companies}

Q1062. Difference between void and return ? Can we have return statement in the void method ?

Core Java

Ans. void is a declaration that states that the method declared void is not expected to return anything.

return is a statement within the method that returns the control out of the method.

Yes, we can have return statement in the void method but without any argument.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve}

Q1063. In Java, if object A contains same the same data of object B, are they equal?

Core Java

Ans. it depends on the implementation of equals method of the respective class. If no definition is provided and it uses the default definition of the object class, two references are equal only if they point to the same object.

We can have such an equality defined for a particular class objects if we provide appropriate implementation of equals method comparing all those fields.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve equals equals method}

Q1064. Is synchronized a keyword , modifier, identifier? what is it ?

Core Java

Ans. synchronized is a keyword and a modifier. The synchronized keyword is used to indicate that a method can be accessed exclusively by one thread at a time.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve synchronization synchronized modifier identifier Asked in 2 Companies}

Q1065. What are access and non access modifiers ?

Core Java

Ans. Access modifiers are the java reserved keywords that changes the access privileges on a class , method , element etc. For example - public , private and protected.

Non Access modifiers are the java modifiers other than access modifiers. For example - static , final, abstract, synchronized, transient, volatile etc.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve access modifiers Asked in 2 Companies}

Q1066. Which of the following applies to Final ?

It is a keyword
It is a modifier
It is an access modifier

Core Java

Ans. It is a keyword and a modifier but not an access modifier.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve keyword modifier}

Q1067. Which of the following applies to "private"?

It is a keyword
It is a modifier
It is an access modifier

Core Java

Ans. Yes, all of them applies to private keyword. It is an access modifier.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve keyword modifier}

Q1068. What is a difference between Identifier and keyword ?

Core Java

Ans. Keyword is a reserved word that has a pre defined meaning for the compiler and hence cannot be used as an identifier, for example - final, private , for etc.

Identifier is the name given by the programmer to a programming construct, for example - class and method names etc.

java Keywords cannot be used as an identifier in java.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve identifier keyword}

Q1069. Can we use java keywords as identifiers ?

Core Java

Ans. No, keyword has pre defined meaning for compiler and hence cannot be used as identifiers.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve keywords identifier}

Q1070. What is the importance of Abstract Class ?

Core Java

Ans. Abstract classes provide a mechanism of interfacing ( using abstract method ) as well as code reuse through inheritance ( extending abstract class )

Comparing to concrete class they have an advantage of providing interface which a concrete class doesn't provide.

Comparing to interfaces they have an advantage of providing code reuse through inheritance which interfaces dont provide.

Sample Code for abstract class

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve abstract class importance of abstract class Basic frequent}

Search Interview Questions

Help us and Others Improve. Please let us know the questions asked in any of your previous interview.