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Interview Questions and Answers for 'Equality' - 11 question(s) found - Order By Newest

Very Very frequently asked. Among the first few questions in almost all interviews.Among Top 5 frequently asked questions.
  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

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   Like      Discuss      Correct / Improve     java   string comparison   string   object class   ==    equals   object equality     Ebay  Cerner  GuideWire  Expeditors Associate  Revature  SAIC  ValueLabs  Realty Redefined  Bank Of America  Capgemini  HCL Technologies  Goldman Sachs  Symmetric Corp  Backstop Solutions  Frontier  IQOR   Science  Vanguard  eClinicalWorks  Experticity  Blue Cross and Blue Shield of Kansas  ComTrade  Banja Luka  Overstock.com  Intrasoft International  IBM  Apex Systems  infoview technologies      basic        frequent

Try 6 Question(s) Test


 Q2. Why is null == null returns true ?Core Java
Admin
info@buggybread.com
Ans. Any reference in java that doesn't point to any object , gets assigned null i.e is a reference to null. Two object references in java are treated equal if they point to the same memory. That's Why null == null results true.

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   Like      Discuss      Correct / Improve     java   null   equality   references


 Q3. What will be the output ?Integer a = 10, b =10;Integer c = 10, d = 1000;System.out.println(a == b);System.out.println(c ==d);Core Java
admin
info@buggybread.com
Ans. truefalse

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   Like      Discuss      Correct / Improve     java   coding   equality   object equality


 Q4. What will the following code print ?

Integer a = 100, b =100;
Integer c = 1000, d = 1000;
System.out.println(a == b);
System.out.println(c ==d);
Core Java

Ans. false
false

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   Like      Discuss      Correct / Improve     object equality  code  coding        frequent


 Q5. 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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   Like      Discuss      Correct / Improve     =  ==  assignment operator  object equality  difference between      Basic


 Q6. 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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   Like      Discuss      Correct / Improve     ==  object equality      Basic


 Q7. What will be the output of following code

Integer x = 1;
Integer y = 2;
System.out.println(x == y);

What if you change 1 to "1" and Integer to String?
Core Java2017-05-07 19:30:13

Ans. It will print "true" with integers as well as strings. The reason is "Integer constant pool" and "String pool"

String pool maintains pool of string literals. When a string literal is used for the first time, a new string object is created and is added to the pool. Upon it's subsequent usage , the reference for the same object is returned. Similarly java uses integer constant pool.

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   Like      Discuss      Correct / Improve     string pool  object equality  ==


 Q8. What will be the output of following code

class TestMain {
public static void main(String[] args) {
String s1 = "ravi";
String s2 = new String("ravi");
Integer i = 10;
Integer a1 = new Integer("10");
System.out.println(s1 == s1);
System.out.println(i == a1);
}
}
Core Java2017-07-17 08:07:19

Ans. false
false

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   Like      Discuss      Correct / Improve     object equality  ==  coding  code     XMSS


 Q9. What will be the output of following ?

String str1 = new String("String1");
String str2 = new String("String1");
System.out.print(str1 == str2);
System.out.print(str1.equals(str2));
str1 = str2;
System.out.print(str1 == str2);
Core Java
a. falsetruetrue
b. truetruetrue
c. truetruefalse
d. falsetruefalse

Ans.a. falsetruetrue

 Q10. What will be the output of following code ?

String str1 = "String1";
String str2 = "String1";
System.out.print(str1 == str2);
System.out.print(str1.equals(str2));
str1 = str2;
System.out.print(str1 == str2);
Core Java
a. falsetruetrue
b. falsefalsetrue
c. truetruetrue
d. falsefalsefalse

Ans.c. truetruetrue

 Q11. 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



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