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

Interview Questions and Answers - Order By Newest

Q1651. What is the difference between double and float variables in Java?

Ans. In java, float takes 4 bytes in memory while Double takes 8 bytes in memory. Float is single precision floating point decimal number while Double is double precision decimal number.

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Q1652. What are Loops in Java? What are three types of loops?

Core Java

Ans. Looping is used in programming to execute a statement or a block of statement repeatedly. There are three types of loops in Java:
1) For Loops
For loops are used in java to execute statements repeatedly for a given number of times. For loops are used when number of times to execute the statements is known to programmer.
2) While Loops
While loop is used when certain statements need to be executed repeatedly until a condition is fulfilled. In while loops, condition is checked first before execution of statements.
3) Do While Loops
Do While Loop is same as While loop with only difference that condition is checked after execution of block of statements. Hence in case of do while loop, statements are executed at least once.

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Q1653. What are the different ways of creating threads in java?

Core Java

Ans. There are two ways to create the threads in java
a) By extending java.lang.Thread class.
b) By implementing java.lang.Runnable interface.

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Q1654. What are the differences between static and non-static methods?

Core Java

Ans. Static method is common to all instances of a class. Static methods are stored in the class memory. Whereas non-static methods are stored in the object memory. Each instance of a class will have their own copy of non-static methods.

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Q1655. How can print the whole object state in the console in javascript ?

Javascript

Ans. We can JSON.stringify

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Q1656. What do you mean by inheritance in java?

Core Java

Ans. Inheritance is one of the key principle of object oriented programming. Through inheritance, one class can inherit the properties of another class. The class from which properties are inherited is called super class and the class to which properties are inherited is called sub class.

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Q1657. What are the fundamental principles of object oriented programming? / What are the OOPs concepts?

Core Java

Ans. a) Inheritance
b) Abstraction
c) Polymorphism
d) Encapsulation

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Q1658. What are the main features of Java?

Core Java

Ans. a) Object Oriented
b) Simple
c) Platform Independent
d) Secured
e) Robust
f) Portable
g) Multithreaded
h) Distributed

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Q1659. How can you trim all strings in an array ?

Ans. array.map(s => s.trim())

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Q1660. Is it safe to use session storage ?

Javascript

Ans. Session storage can be accessed from XSS (Cross site Scripting) attacks but cookies (if set with "HttpOnly" and "Secure" flags) are more safer against these attacks.

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Q1661. Can we initialize final fields within the constructor ? Why ?

Core Java

Ans. Yes, Because final fields needs to be initialized before the construction of the object completes. Not necessarily at the time of class loading.

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Q1662. What is Array.Map function ? What will be output of following ?

const myArray = [1, 4, 9, 16];
const result = myArray.map(x => x * 2);

Javascript

Ans. It will create an array with each value as x*2

[2, 8, 18, 32]

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Q1663. When String literals are compared using ==, they always returns true if the string values are same because .. Reference

Core Java

a. of overridden compareTo method

b. of overridden compare method

c. of String Pool

d. == means that the object contents are equal

Ans.c. of String Pool

Q1664. Which of the following is true ?

Core Java

a. Composition is Tightly Bound

b. Inheritance is Tightly Bound

c. Object can only hold reference of only one other object

d. A Class cannot be extended by multiple classes

Ans.b. Inheritance is Tightly Bound

Q1665. In case of String Literals .. Reference

Core Java

a. x==y on all literals always returns false

b. x.equals(y) on all literals always returns false

c. if x.equals(y) returns true, x==y returns true too

d. if x.equals(y) returns false, x==y returns true

Ans.c. if x.equals(y) returns true, x==y returns true too

Q1666. What is a default constructor ? Reference

Core Java

a. Constructor without parameters declared by user

b. Constructor provided by Java if no constructor is declared

c. Constructor with empty body

d. All of the above

Ans.b. Constructor provided by Java if no constructor is declared

Q1667. How can we create objects if we make the constructor private ?

Core Java

a. We can't create objects if constructor is private

b. We can only create objects if we follow singleton pattern

c. We can only create one object

d. We can create new object through static method or static block

Ans.d. We can create new object through static method or static block

Q1668. 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

Q1669. 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

Q1670. What will be the output of following code ?

String str1 = "String1";
String str2 = "String2";
str1.concat("String3");
System.out.print(str1);
System.out.print(str2);

Core Java

a. String1String2

b. String1String3String3

c. String1String3String1String3

d. String1String1

Ans.a. String1String2

Q1671. What will be the output of following code ?

String str1 = "String1";
String str2 = "String2";
str1=str1.concat("String3");
System.out.print(str1);
System.out.print(str2);

Core Java

a. String1String2

b. String1String3String2

c. String1String2String3

d. String1Stringg3String1

Ans.b. String1String3String2

Q1672. Which method needs to be implemented if a class is implementing comparable interface ?

Core Java

a. comp

b. compare

c. compareTo

d. compareEquals