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

Interview Questions and Answers - Order By Newest

Q701. Is array an object in Java ? How can you prove that ?

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}

Q702. 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}

Q703. 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}

Q704. 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}

Q705. 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}

Q706. 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}

Q707. 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}

Q708. 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}

Q709. 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}

Q710. 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}

Q711. 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}

Q712. 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}

Q713. 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}

Q714. 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}

Q715. 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}

Q716. 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}

Q717. 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}

Q718. 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}

Q719. 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}

Q720. 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}

Q721. Can we use true and false as identifiers in java ? Are they keywords in Java ?

Core Java

Ans. true and false are literals in java. No we cannot use them as identifiers.

Sample Code for literal

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

_{Like Discuss Correct / Improve identifiers keywords literals}

Q722. What are the some literals in java that are reserved and hence cannot be used as identifiers ?

Core Java

Ans. true , false and null

Sample Code for literals

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

_{Like Discuss Correct / Improve literals}

Q723. What is the use of java.util.concurrent package in Java ?

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 java.util.concurrent}

Q724. How is garbage collection in Java 8 different from Java 7 ?

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 memory management garbage collection}

Q725. How can you extract integers from string values and add (sum it up) all the extracted integers? e.g "James34long4island322in3rdAvenue" ---> 34 4 322 3 = 363

Core Java

^{This question was recently asked at 'Horizon Solutions'.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 coding code Asked in 1 Companies}

Q726. Which of the two - compile time and run time polymorphism - requires signature of the method to be different ?

Core Java

Ans. runtime polymorphism or method overriding doesn't require method name and signature to be different whereas compile time polymorphism or method overloading requires method name to be same but the signature to be different.

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

_{Like Discuss Correct / Improve polymorphism object oriented programming (oops) oops concepts overloading overriding basic}

Q727. Write a class and override the equals and hashcode method ?

Core Java

Ans. class Student
{
///
///
///
private int id;
private String name;

///
///
///
public Student(int id, String name)
{
this.name = name;
this.id = id;

}// Student

///
///
///
public int getId()
{
return id;

}// getId

///
///
///
public void setId(int id)
{
this.id = id;

}// setId

///
///
///
public String getName()
{
return name;

}// getName

///
///
///
public void setName(String name)
{
this.name = name;

}// setName

@Override
public boolean equals(Object obj)
{
if (obj == null) return false;
if (!(obj instanceof Student))
return false;
if (obj == this)
return true;

return this.getId() == ((Student) obj).getId();

}// equals

///
///
///
@Override
public int hashCode()
{
return this.getId();

}// hashCode

}// Student

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

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

Q728. Write a Program to convert a binary to number ?

Core Java

Ans. int convert(int binaryInt) {
int sumValue=0;
int multiple = 1;
while(binaryInt > 0) {
binaryDigit = binaryInt;
binaryInt = binaryInt /10;
sumValue = sumValue (binaryDigit * multiple);
multiple = multiple * 2;
}

return sumValue;
}

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

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

Q729. What is the use of Annotations in Java ?

Core Java

Ans. Annotations are used to specify meta information about the code.

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

_{Like Discuss Correct / Improve Annotations}

Q730. Are Annotations better than using XML configs ?

Core Java

Ans. Yes , as both code and its meta information reside in the same file, it promotes better readability and maintenability.

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

_{Like Discuss Correct / Improve Annotations}

Search Interview Questions

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