Java programming interview questions and answers for experienced

Posted by: Instanceofjava Posted date: July 16, 2016 / comment : 1 ,

  • Here some of the java programming interview questions and answers for experienced on different topics.
  • Java interview programs and answers for experienced.
  • Java Coding interview Questions
  • Java tricky interview programs to practice.




 Program #1: what will happen if we try to print null using system.out.println

  1. package interviewprograms.instanceofjava;
  2. public class InterviewProgram {
  3.  
  4.     /**
  5.      * @java programming interview questions and answers for freshers and experienced
  6.      */
  7.     public static void main(String[] args) {
  8.         
  9.         System.out.println(null);
  10.  
  11.     }
  12.  
  13. }






Program #2: Java Interview program :Can we create object for abstract class in same class

  1. package interviewprograms.instanceofjava;
  2. public abstract class AbstractDemo {
  3.  
  4. public static void main(String args[]){
  5.         
  6.         AbstractDemo obj = new AbstractDemo();
  7.         
  8.  }
  9.  
  10. }





Program #3: Java Interview program : what will be the output of below java program


Java programming interview questions and answers for experienced





 Program #4: Guess the order of execution of constructors

  1. package interviewprograms.instanceofjava;
  2. public class ConstructorDemo {
  3.  
  4. ConstructorDemo(){
  5.         this(1);
  6.         System.out.println("Zero argument constructor");
  7. }
  8.     
  9. ConstructorDemo(int a){
  10.         this("Hi",1);
  11.         System.out.println("One argument constructor");
  12. }
  13.  
  14. ConstructorDemo(String str, int x){
  15.     
  16.         System.out.println("Two argument constructor");
  17. }
  18.  
  19. public static void main(String[] args) {
  20.  
  21.         ConstructorDemo obj =new ConstructorDemo();
  22.  
  23.     }
  24.  
  25. }





How to find Biggest Substring in between specified character or String

Posted by: Instanceofjava Posted date: February 09, 2016 / comment : 3 ,

1. Java Program to find biggest substring in between specified character or string

String: i am rajesh kumar ravi

in between: 'a'

 

  1. package com.instaceofjava;
  2.  
  3. public class BiggestSubString{
  4.  
  5. public static void main(String[] args) {
  6.  
  7. String str="i am rajesh kumar ravi";
  8.  
  9.  String longest="";
  10.  int maxlength=0;
  11.  
  12.  String arr[]=str.split("a");
  13.  
  14. for (int i = 1; i < arr.length-1; i++) {
  15.  
  16.    System.out.println(arr[i]); // printing substrings
  17.  
  18.           if(arr[i].length() > maxlength){
  19.                maxlength = arr[i].length();
  20.                 longest = arr[i];
  21.             }   
  22.  
  23.    }      
  24.   
  25. System.out.println("Longest substring is: "+longest);
  26.  
  27. }
  28. }


Output:

  1. m r
  2. jesh kum
  3. r r
  4. Longest substring is: jesh kum


Java Basic Interview Programming Questions on Constructors

Posted by: Instanceofjava Posted date: February 07, 2016 / comment : 6 ,

  • Below programs are the basic programs frequently asking in java quizzes  try to test your java programming skills by answering the questions. if you are having any doubts feel free to ask us.
  • Java Coding Questions on constructors.
1.What will be the Output of this program.

  1. public class Test1{
  2.  
  3. Test1(int i){
  4.  
  5. System.out.println("Test1 Constructor "+i);
  6.  
  7.  } 
  8. }

  1. public class Test2{
  2.  
  3. Test1 t1= new Test1(10);
  4.  
  5. Test2(int i){
  6.  
  7.  System.out.println("Test2 Constructor "+i);
  8.  
  9. } 

  11. public static void main(String[] args) {
  12.  
  13.         Test2 t2= new Test2(5);
  14.  
  15.     }
  16. }







 2.What will be the Output of this program.

  1. public class A{
  2.  
  3. A(){
  4.  
  5.   System.out.println("A Class Constructor ");
  6.  
  7. }
  8.  
  9. }

  1. public class B extends A{
  2.  
  3. B(){
  4.  
  5.   System.out.println("B Class Constructor ");
  6.  
  7. }
  8. public static void main(String[] args) {
  9.  
  10.         B ob= new B();
  11.  
  12.     }
  13. }







 3.What will be the Output of this program.

  1. public class  A{
  2.  
  3. A(){

  5. this(0);
  6. System.out.println("Hi ");
  7.  
  8. } 
  9.  
  10. A(int x){

  12. this(0,0);
  13. System.out.println("Hello");
  14.  
  15. }
  16.   
  17. A(int x, int y){
  18.  
  19. System.out.println("How are you");
  20.  
  21. }
  22. public static void main(String[] args) {
  23.  
  24.         A ob= new A();
  25.  
  26.     }
  27. }




Bubble sort algorithm in java with example

Posted by: Instanceofjava Posted date: December 28, 2015 / comment : 0 ,

  Java Program to sort array using bubble sort

  1. package com.instaceofjava; 

  3. public class BubbleSortExample{
  4.   
  5. int[] array={4,2,5,6,9,1};
  6.  
  7. int n = array.length;
  8. int k;
  9.  
  10. for (int m = n; m>= 0; m--) {
  11.  
  12. for (int j = 0; j < n-1; j++) {
  13.  
  14.    k = j + 1;
  15.  
  16.  if (array[j] > array[k]) {
  17.  
  18.        int temp;
  19.        temp = array[j];
  20.        array[j] = array[k];
  21.        array[k] = temp;
  22.  
  23. }
  24. }
  25.            
  26. for (int x = 0; x < array.length; x++) {
  27.  
  28. System.out.print(array[x] + ", ");
  29.  
  30.  }
  31.  
  32. System.out.println();
  33. }  
  34.  
  35. }
  36.  
  37. }



Output:

  1. 2, 4, 5, 6, 1, 9, 
  2. 2, 4, 5, 1, 6, 9, 
  3. 2, 4, 1, 5, 6, 9, 
  4. 2, 1, 4, 5, 6, 9, 
  5. 1, 2, 4, 5, 6, 9, 
  6. 1, 2, 4, 5, 6, 9, 
  7. 1, 2, 4, 5, 6, 9,



AtomicInteger in Java

Posted by: Instanceofjava Posted date: December 26, 2015 / comment : 0


  • Java.util.concurrent.atomic package provides very useful classes that support lock free and thread safe programming.
  • The main use of this class is an int value that may be updated automatically.
  • AtomicInteger has some useful methods. Before that lets see the some points about this class.
  • Commonly we will use this AtomicInteger to handle the counter that is accessible by different threads simultaneously.

Java.util.concurrent.atomic.AtomicInteger:

  1. public class AtomicInteger
  2. extends Number
  3. implements Serializable

AtomicInteger Class Constructors:


  • public AtomicInteger(): Creates a new AtomicInteger object with default value 0.
  1. AtomicInteger atomicInteger = new AtomicInteger();
  • public AtomicInteger(int initialValue): Creates a new AtomicInteger object with given initial  value.
  1. AtomicInteger atomicInteger = new AtomicInteger(10);


 AtomicInteger Class Methods:


 1.public final void set(int newValue):
  •  Sets given value to the object.

  Java Program to create AtomicInteger class object and sets some value.

  1. package com.instaceofjava;
  2.  
  3. import java.util.concurrent.atomic.AtomicInteger;
  4.  
  5. public class AtomicIntegerExample{
  6.  
  7. public static void main(String[] args) {
  8.  
  9. AtomicInteger atomicInteger = new AtomicInteger();
  10.  
  11.   System.out.println(atomicInteger);
  12.   atomicInteger.set(10);
  13.   System.out.println(atomicInteger);
  14.  
  15. }
  16.  
  17. }

Output:

  1. 0
  2. 10

2, public final void get():

  • Used to get current value.

Java Program to create AtomicInteger class object and sets some value and get.

  1. package com.instaceofjava;
  2.  
  3. import java.util.concurrent.atomic.AtomicInteger;
  4.  
  5. public class AtomicIntegerExample{
  6.  
  7. public static void main(String[] args) {
  8.  
  9. AtomicInteger atomicInteger = new AtomicInteger();
  10.  
  11.   System.out.println(atomicInteger.get());
  12.   atomicInteger.set(10);
  13.   System.out.println(atomicInteger.get());
  14.  
  15. }
  16.  
  17. }

Output:

  1. 0
  2. 10
3.public final int getAndSet(int newValue):
  • Automatically sets the given value and returns old value.

  Java Program which explains getAndSet(int x) method of AtomicInteger class

  1. package com.instaceofjava;
  2.  
  3. import java.util.concurrent.atomic.AtomicInteger;
  4.  
  5. public class AtomicIntegerExample{
  6.  
  7. public static void main(String[] args) {
  8.  
  9. AtomicInteger atomicInteger = new AtomicInteger();
  10.  
  11.    System.out.println(atomicInteger.get());
  12.  
  13.    atomicInteger.set(10);
  14.  
  15.    System.out.println(atomicInteger.get());
  16.  
  17.    System.out.println(atomicInteger.getAndSet(12));
  18.  
  19.    System.out.println(atomicInteger.get());
  20.  
  21. }
  22.  
  23. }

Output:

  1. 0
  2. 10
  3. 10
  4. 12



4.public final int incrementAndGet()
  • Automatically increments the value one and returns updated value

  Java Program which explains incrementAndGet() method of AtomicInteger class

  1. package com.instaceofjava;
  2.  
  3. import java.util.concurrent.atomic.AtomicInteger;
  4.  
  5. public class AtomicIntegerExample{
  6.  
  7. public static void main(String[] args) {
  8.  
  9. AtomicInteger atomicInteger = new AtomicInteger();
  10.  
  11.    System.out.println(atomicInteger.get());
  12.  
  13.    atomicInteger.set(10);
  14.  
  15.    System.out.println(atomicInteger.get());
  16.  
  17.    System.out.println(atomicInteger.incrementAndGet());
  18.  
  19.  
  20. }
  21.  
  22. }

Output:

  1. 0
  2. 10
  3. 11


How to create immutable class in java

Posted by: Instanceofjava Posted date: December 24, 2015 / comment : 0

  • In Java String and all wrapper classes are immutable classes.
  • So how to create custom immutable class in java?
  • Lets see how to make a class object immutable.

  Immutable class:

  • Make class final so that it should not be inherited.
  • All the variables should be private so should not be accessible outside of class. 
  • Make all variables final so that value can not be changed.
  • A constructor to assign values to variables in class.
  • Do not add any setter methods.

1. Java Program to create custom immutable class object in java.

  1. package com.instaceofjava;

  3.  
  4. public final class ImmutableClass{
  5.   
  6. private final int a;
  7. private final int b;
  8.  
  9. ImmutableClass( int x, int y){
  10.  
  11.  a=x;
  12.  b=y; 

  14. } 
  15.  
  16. public getA(){
  17.  
  18.  return a;

  20. }
  21.  
  22. public getB(){
  23.  
  24.  return b;

  26. }
  27.  
  28. public static void main(String[] args) {
  29.  
  30. ImmutableClass obj= new ImmutableClass(10,20);
  31.  
  32. System.out.println("a="+obj.getA());
  33.  
  34. System.out.println("b="+obj.getB());
  35.  
  36. }
  37. }
Output:

  1. a=10
  2. b=20


String class in java: Immutable
  1. public final class String
  2.         implements java.io.Serializable, Comparable<String>, CharSequence
  3. {  
  4.   
  5. //String class variables

  7.   private final char value[];
  8.   private final int offset;
  9.   private final int count;
  10.   private int hash; // Default to 0
  11.   private static final ObjectStreamField[] serialPersistentFields =
  12.       new ObjectStreamField[0];
  13.   
  14. //String class constructor
  15. public String(String original) {
  16.  
  17.             int size = original.count;
  18.              char[] originalValue = original.value;
  19.              char[] v;
  20.              if (originalValue.length > size) {
  21.                 // The array representing the String is bigger than the new
  22.               // String itself.  Perhaps this constructor is being called
  23.                 // in order to trim the baggage, so make a copy of the array.
  24.                  int off = original.offset;
  25.                 v = Arrays.copyOfRange(originalValue, off, off+size);
  26.             } else {
  27.                  // The array representing the String is the same
  28.                  // size as the String, so no point in making a copy.
  29.                  v = originalValue;
  30.            }
  31.             this.offset = 0;
  32.              this.count = size;
  33.             this.value = v;
  34.         } 

  36. }



Java Program to find Sum of Digits

Posted by: Instanceofjava Posted date: December 20, 2015 / comment : 3


1. Java Program to find sum of digits without using recursion.

  1. package com.instaceofjava;
  2. import java.util.Scanner;
  3.  
  4. public class SumOfDigits {
  5.  
  6. public static void main(String[] args) {
  7.  
  8. int number;
  9. Scanner in = new Scanner(System.in);
  10.  
  11. System.out.println("Please Enter a number");
  12.  
  13. number=in.nextInt(); 
  14.  
  15. int sum=0 ;
  16.  
  17. while(number!=0){
  18.  
  19. sum=sum+(number%10);
  20. number=number/10;
  21. }
  22.  
  23. System.out.println("Sum of Digits ="+sum);
  24.  
  25. }
  26. }
Output:

  1. Please Enter a number
  2. 123
  3. Sum of Digits=6


2. Java Program to find sum of digits using recursion.

  1. package com.instaceofjava;
  2. import java.util.Scanner;
  3.  
  4. public class SumOfDigits {
  5.  
  6. int sum;

  8. public int CalRecSum(int n){
  9.  
  10. if(n==0){
  11. return sum;
  12. }
  13. else{
  14.  
  15.  sum+=n%10;
  16.  CalRecSum(n/10);
  17.  
  18. } 
  19.  
  20. return sum;
  21. }

  23. public static void main(String[] args) {
  24.  
  25. int number;
  26. Scanner in = new Scanner(System.in);
  27.  
  28. System.out.println("Please Enter a number");
  29.  
  30. number=in.nextInt(); 
  31.  
  32. SumOfDigits   ob= new SumOfDigits();
  33. System.out.println("Sum of Digits ="+ob.CalRecSum(number));
  34.  
  35. }
  36.  
  37. }


Output:

  1. Please Enter a number
  2. 326
  3. Sum of Digits=11

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