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Core Java - Interview Questions and Answers for 'Operator' - 30 question(s) found - Order By Newest

Very frequently asked. Among first few questions in almost all interviews. Among Top 5 frequently asked questions. Frequently asked in Indian service companies (HCL,TCS,Infosys,Capgemini etc based on multiple feedback )
  Q1. Difference between == and .equals() ?Core Java
Anonymous
Ans. "equals" is the method of object class which is supposed to be overridden to check object equality, whereas "==" operator evaluate to see if the object handlers on the left and right are pointing to the same object in memory.

x.equals(y) means the references x and y are holding objects that are equal. x==y means that the references x and y have same object.

Sample code:

String x = new String("str");
String y = new String("str");

System.out.println(x == y); // prints false
System.out.println(x.equals(y)); // prints true

  Sample Code for equals

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Try 6 Question(s) Test


Frequently asked in Infosys and HCL Technologies ( Based on 2 feedback )
 Q2. What are different ways of object creation in Java ?Core Java
Admin
info@buggybread.com
Ans. Using new operator - new xyzClass()

Using factory methods - xyzFactory.getInstance( )

Using newInstance( ) method - (Class.forName(xyzClass))emp.newInstance( )

By cloning an already available object - (xyzClass)obj1.clone( )

  Sample Code for object initialization using clone

  Sample Code for object initialization using getInstance

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   Like      Discuss      Correct / Improve     java   oops   object creation   new operator   class.forname   cloning   ebay     Intelligrape  Infosys  Polaris  British Telecom (BT)  Vyom Labs  Deutsche Bank  HCL Technologies   Genpact  Thomson Reuters      expert


 Q3. What is the difference between the following two code lines ?

1. new OuterClass().new InnerClass();

2. new OuterClass.InnerClass();
Core Java2016-06-30 14:45:37

Ans. In first case we are trying to initialize Inner class object using the instance of Outer Class whereas in second case we are trying to initialize the Inner class object directly using the Outer class name.

In second case , Inner class is "static inner class" as we cannot access "non static inner class" using Classname alone.

In first case, the inner class could be either "static inner class" or "non static inner class".

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   Like      Discuss      Correct / Improve     inner classes  inner class   static inner class   new operator


Usually asked in relation to casting and ClassCastException.
 Q4. What is instanceOf operator ? Explain it's use ?Core Java2017-06-12 07:58:22

Ans. The operator instanceOf is used to verify if the specified object is the instance of specified class or interface.

Syntax if(x instanceOf ABC)

where x is an object reference and ABC could be a class name or interface name. The above statement will be true if x holds an object that is an instance of ABC or any of the child class of ABC or if x holds an object that implements ABC.

instanceOf operator is used to verify in case of downcasting. For ex -

DerivedClass extends BaseClass

x is the reference of BaseClass but holds DerivedClass object ( Polymorphism )

There is an operation that is defined in Derived Class, let's say derivedClassMethod()

We cannot call derivedClassMethod() directly using x as x is reference of BaseClass and not DerivedClass and hence can only access methods that are defined in BaseClass and overridden in derived class.

Though we can cast it to DerivedClass as following
((DerivedClass)x).derivedClassMethod();

But it may throw ClassCastException in case x doesn't hold an instance of DerivedClass at that point.

So before casting it to DerivedClass we may like to make sure that it is an instance of DerivedClass and hence won't throw ClassCastException.

So we make a check for it

if(x instanceOf DerivedClass) {
((DerivedClass)x).derivedClassMethod();
}

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   Like      Discuss      Correct / Improve     instanceOf  instanceOf operator  Why we need instanceOf operator  use of instanceOf operator     Trimax IT Infrastructure & Services   ultramain      Intermediate        frequent


 Q5. According to Java Operator precedence, which operator is considered to be with highest precedence?Core Java
Admin
info@buggybread.com
Ans. Postfix operators i.e () [] . is at the highest precedence.

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   Like      Discuss      Correct / Improve     java   operators   operator precedence     Palpap Ichinichi  Veritas


 Q6. Difference between new operator and Class.forName().newInstance() ?
Admin
info@buggybread.com
Ans. new operator is used to statically create an instance of object. newInstance() is used to create an object dynamically ( like if the class name needs to be picked from configuration file ). If you know what class needs to be initialized , new is the optimized way of instantiating Class.

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   Like      Discuss      Correct / Improve     java   oops   object instantiation   object creation   class.forname   newinstance   new operator   difference between   advanced      intermediate


 Q7. How to find whether a given integer is odd or even without use of modulus operator in java?Core Java
Admin
info@buggybread.com
Ans. public static void main(String ar[])
{
int n=5;
if((n/2)*2==n)
{
System.out.println("Even Number ");
}
else
{
System.out.println("Odd Number ");
}
}

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 Q8. Difference between Class#getInstance() and new operator ?
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info@buggybread.com
Ans. Class.getInstance doesn't call the constructor whereas if we create an object using new operator , we need to have a matching constructor or copiler should provide a default constructor.

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 Q9. What is the difference between >> and >>>?
Admin
info@buggybread.com
Ans. Both bitwise right shift operator ( >> ) and bitwise zero fill right shift operator ( >>> ) are used to shift the bits towards right. The difference is that >> will protect the sign bit whereas the >>> operator will not protect the sign bit. It always fills 0 in the sign bit.

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 Q10. Which Java operator is right associative?Core Java
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Ans. The = operator is right associative.

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 Q11. In which cases isn't instanceof operator a bad practice?Core Java
Admin
info@buggybread.com
Ans. To avoid ClassCastException.

Though the following code will compile fine but will result in ClassCastException during runtime.

Fruit fruit = new Apple();
Banana banana = Banana(fruit); // ClassCastException


This code will not give compile time error as Banana and Fruit are related as Banana either extends or implement Fruit, So downcasting is acceptable. With this code we assume that the Fruit handler will have the Apple object at that point, violating which the code will throw the exception.

This exception can be avoided by following code.

Fruit fruit = new Apple();
if(fruit instanceOf Banana){
Banana banana = Banana(fruit); // ClassCastException
}

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 Q12. Difference between prefix and postfix increment operator ?
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Ans. Prefix operator performs the increment and then assignment whereas its inverse for postfix operator.

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   Like      Discuss      Correct / Improve     prefix increment operator   postfix increment operator   operators   java      basic        frequent


 Q13. Write code to check if an integer is odd or even using ternary operator

Ans. http://javasearch.buggybread.com/CodeSnippets/searchCodeSamples.php?&category=code&searchOption&keyword=963

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 Q14. What is Associativity while evaluating a Java statement ?Core Java

Ans. Associativity determines whether an expression is evaluated left-right or right-left. When an expression has two operators with the same precedence, the expression is evaluated according to its associativity.

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 Q15. Is New Keyword a method Name ?Core Java2016-06-12 20:15:01

Ans. No, Its an Operator.

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Rarely asked as it was introduced with Java 8.
 Q16. What is the use of :: operator wef from Java 8 ?Core Java2016-07-25 13:27:57

Ans. We can refer to a function using this operator like System.out.println(intList.stream().reduce(Math::max).get());

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 Q17. What is the difference between = and == in Java ?Core Java2016-09-02 08:12:45

Ans. = is the assignment operator that assigns the result of the expression on the right to the variable on the left, whereas

== is the operator to check object equality to see if the reference on left and right are pointing to the same object. For primitive types, its used to check if both variables holds the same value.

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 Q18. How is == operator different for objects and primitive types ? Core Java2016-09-02 08:14:44

Ans. For objects or references, == operator check if the reference on left and right points to the same object.

For primitive types or variables, == operator check if the variable on left and right holds the same value.

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 Q19. Which operators in Java have highest precedence ?Core Java2017-01-07 17:00:43

Ans. Braces, i.e () and [] have the highest precedence

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 Q20. Does java supports operator overloading ?Core Java2017-01-09 09:40:40

Ans. No

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 Q21. Is there a way to know size of an object in Java ?Core Java2017-01-12 11:14:59

Ans. No, Java doesn't have a sizeOf operator. In C / C++ , its required to determine how much memory allocation is required which is not the case with Java. Java handles memory allocation and deallocation intrinsically.

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 Q22. Explain dot(.) operator ?Core Java2017-01-19 13:53:35

Ans. Its used to access the object properties using the object reference or class properties using the Class Name. Moreover its used to access the classes and Interfaces of a package.

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 Q23. What are the different operators in Java ?Core Java2017-01-28 15:15:36

Ans. && - AND
|| - OR
! - LOGICAL NOT

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 Q24. What is the difference between && and & in Java ?Core Java2017-02-03 08:30:47

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


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   Like      Discuss      Correct / Improve     operators  logical vs bitwise operator


 Q25. What is the precedence of operators in Java ?Core Java2017-03-01 09:42:52

Ans. http://introcs.cs.princeton.edu/java/11precedence/

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 Q26. Which of the following is valid greater than and equal to operator in Java ?

>=
=>
Core Java2017-05-20 16:23:47

Ans. >=

=> will result in error.

=> somewhat looks like lambda operator "->"

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 Q27. What is a ternary operator ?Database2017-06-18 16:46:34

Ans. Ternary operator , also called conditional operator is used to decide which value to assign to a variable based on a Boolean value evaluation. It is used as

condition ? value1 : value2

For example

int y = (x > 0) ? x:0; // assign x if it's greater than 0, else assign 0

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   Like      Discuss      Correct / Improve     operator  ternary operator      Basic


 Q28. Why doesn't java support operator overloading ?Core Java2017-06-23 08:15:18

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


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 Q29. Which of the following is true for == operator ?Core Java
a. For primitives, == checks if the variables on left and right have same data type
b. For primitives, == checks if the variables on left and right have same value
c. For Objects, == checks if the references on left and right have same data type
d. For Objects, == checks if the references on left and right have same value

Ans.b. For primitives, == checks if the variables on left and right have same value

 Q30. Which of the following is equivalent to following logic ?

Not X && Not Y
Core Java
a. x || Y
b. Not(X || Y)
c. Not(X && Y)
d. Not X && Y

Ans.b. Not(X || Y)



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