InstanceOfJava: Core java Interview Questions

How to read a file in java with example program

Posted by: Instanceofjava Posted date: August 27, 2016 / comment : 0 Core java Interview Questions , java programming interview questions

We can read java file using buffered reader class in java
We need to import java.io.BufferedReader in order to read java text file.
Create object of java.io.BufferedReader class by passing new FileReader("C:\\Sample.txt") object to the constructor.
In order to read line by line call readLine() method of BufferedReader class which returns current line. Initially first line of java text file

Program #1: Write a java program to read a file line by line using BufferedReader class

package com.instanceofjava.javareadfile;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
public class ReadFileBufferedReader {
/**
* @Website: www.instanceofjava.com
* @category: How to read java read file line by line using buffered reader
*/
public static void main(String[] args) {
BufferedReader breader = null;
try {
String CurrentLine;
breader = new BufferedReader(new FileReader("E://Sample.txt"));
while ((CurrentLine = breader.readLine()) != null) {
System.out.println(CurrentLine);
}
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if (breader != null)
breader.close();
} catch (IOException ex) {
ex.printStackTrace();
}
}
}
}

Output:

Java open and read file
Read file line by line in java
Example java program to read a file line by line
java read file line by line example

Program #2: Write a java program to read a file line by line using BufferedReader class using Eclipse

Can an abstract class have a constructor in Java

Posted by: Instanceofjava Posted date: August 26, 2016 / comment : 0 Core java Interview Questions , java programming interview questions

Yes we can define a constructor in abstract class in java.

Then next question will come like when we can not create object of abstract class then why to define constructor for abstract class.
It is not possible to create object of abstract class directly but we can create object of abstract class from sub class which is actually extending abstract class.
When we define a abstract class a class must extend that abstract class then only there will be use of that class
Then when we create object of class which extends abstract class constructor of sub class will be called from that abstract class constructor will be called and memory will be created for all non static members.
If we are not defining any constructor default constructor will be executed.
So we can define any number of constructor in abstract class.
And it is recommended to define constructor as protected. Because there is only one scenario which we can create object is from subclass so define abstract class constructor as protected always.

Order of execution of constructor in Abstract class and its sub class.

When we create object of class which is extending abstract class then it will call abstract class constructor through sub class constructor.
Lest see a java example program on abstract class constructor in java

Program #1: Does abstract class have constructor???

package com.instanceofjava.abstractclassconstructor;
public abstract class AbstractDemo {
AbstractDemo(){
System.out.println("No argument constructor of abstract class");
}
}

package com.instanceofjava.abstractclassconstructor;
public class Test extends AbstractDemo{
Test(){
System.out.println("Test class constructor");
}
public static void main(String[] args) {
Test obj = new Test();
}
}

Output:

No argument constructor of abstract class
Test class constructor

Can we define parameterized constructor in abstract class?

Yes we can define parameterized constructor in abstract class.
But we need to make sure that the class which is extending abstract class have a constructor and it should call super class parameterized constructor
We can call super class parameterized constructor in sub class by using super() call
For example: Super(2) ;
What will happen if we are not placing super call in sub class constructor?
Compiler time error will come.

Program #2: Can we define parameterized constructor in abstract class in java?

package com.instanceofjava.abstractclassconstructor;
public abstract class AbstractDemo {
AbstractDemo( int x){
System.out.println("No argument constructor of abstract class x="+x);
}
}

package com.instanceofjava.abstractclassconstructor;
public class Test extends AbstractDemo{
Test(){
super(10);
System.out.println("Test class constructor");
}
public static void main(String[] args) {
Test obj = new Test();
}
}

Output:

No argument constructor of abstract class x=10
Test class constructor

Program #3: What will happen if we are not placing super call in sub class constructor?

does abstract class have constructor in java

Static method vs final static method in java with example programs

Posted by: Instanceofjava Posted date: August 21, 2016 / comment : 4 Core java Interview Questions , java programming interview questions

Static methods are class level so there are not part of object.
So we can not override static methods but we can call super class static method using subclass name or instance also.
If we are trying to override static methods in sub class from super class then it will be method hiding not method overriding.

Means whenever we call the static method on super class will call super class static method and if we are calling method using sub class it will call sub class method.
So it is clear that static methods are hidden not overridden and they are part of class means class level not object level.
Now the question is can a method be static and final together?
For non static methods if we declare it as final then we are preventing that method from overriding so it can not be overridden in sub class.
When we declare static method as final its prevents from method hiding.
When we declare final static method and override in sub class then compiler shows an error
Compile time error: Cannot override the final method from Super
Lets see an example program to understand this better.

Static methods in java

Program #1: Java example program to explain about static method in java

package inheritanceInterviewPrograms;
/*
* @website: www.instanceofjava.com
* @category: Deference between staic and final static methods in java
*/
public class Super {
static void method(){
System.out.println("Super class method");
}
}

package inheritanceInterviewPrograms;
// www.instanceofjava.com
public class Sub extends Super {
static void method(){
System.out.println("Sub class method");
}
public static void main (String args[]) {
Super.method();
Sub.method();
}
}

Output:

Super class method
Sub class method

When we override static methods its not overriding it is method hiding and whenever we call method on class name it will call corresponding class method.
If we call methods using objects it will call same methods.

Program #2: Java example program to explain about calling super class static method using sub class in java

package inheritanceInterviewPrograms;
/*
* @website: www.instanceofjava.com
* @category: Deference between staic and final static methods in java
*/
public class Super {
static void method(){
System.out.println("Super class method");
}
}

package inheritanceInterviewPrograms;
// www.instanceofjava.com
public class Sub extends Super {
public static void main (String args[]) {
Super.method();
Sub.method();
}
}

Output:

Super class method
Super class method

We can call super class static methods using sub class object or sub class name also.
Now lets see what will happen in final static methods

Final static methods in java:

Can a method be static and final together in java?
When we declare a method as final we can not override that method in sub class.
In the same way when we declare a static method as final we can not hide it in sub class means we can not create same method in sub class.
If we try to create same static method in sub class compiler will throw an error.
Lets see a java example program on final static methods in inheritance.

Program #3: Java example program to explain about final static method in java

package inheritanceInterviewPrograms;
/*
* @website: www.instanceofjava.com
* @category: Deference between staic and final static methods in java
*/
public class Super {
final static void method(){
System.out.println("Super class method");
}
}

package inheritanceInterviewPrograms;
// www.instanceofjava.com
public class Sub extends Super {
static void method(){ // compiler time error:
System.out.println("Sub class method");
}
public static void main (String args[]) {
Super.method();
Sub.method();
}
}

Output:

difference between static method and final method in java

How to take input from user in java using scanner

Posted by: Instanceofjava Posted date: August 19, 2016 / comment : 0 Core java Interview Questions , java programming interview questions

We are having special classes to take input from the user. One of the most commonly used class is java.util.Scanner.
We can read input from the console using scanner class.
Java.util.Scanner class provides lot of methods to take different typed of data from the user as input.
Scanner class is final class in java like String class.
Scanner class implements Iterator and Closeable interfaces.

Scanner class in Java

public final class Scanner
extends Object
implements Iterator<String>, Closeable

In order to read or take input from user we need to create object of Scanner class by using its constructor which takes System.in as an argument.
By using methods of System class we can take different type of data like string , int and float etc.
scannerObject.nextInt() will accepts integer value as an input .
scannerObject.nextLong() will accepts long value as an input from user.
We also take different type of data by using some delimiters
Using useDelimiter() method we can give data by using delimiters.
Lets see what are the different methods in java.util.scanner class.

Java.util.Scanner class methods:

Scanner class in java programming:

Lets see some simple java programs to get input from user
How to take integer input from user in java?
How to take input from user in java using scanner ?
How to take string input in java using scanner class?

Program #1: Write a java example program to read integer type of data as an input from the user from console using scanner class

package com.scannerjava;
import java.util.Scanner;
public class TakeInputUsingScanner {
/**
* @wesite:www.instanceofJava.com
* @category: Java program to take input from user using scanner
*/
public static void main(String[] args) {
Scanner sc= new Scanner(System.in);
System.out.println("Please enter any integer value as input");
int x=sc.nextInt();
System.out.println("Entered integer value is "+x);
}
}

Output:

Please enter any integer value as input
33
Entered integer value is 33

Program #2: Write a java example program to read String type of data as an input from the user from console using scanner class

package com.scannerjava;
import java.util.Scanner;
public class TakeInputUsingScanner {
/**
* @wesite:www.instanceofJava.com
* @category: Java program to take input from user using scanner
*/
public static void main(String[] args) {
Scanner sc= new Scanner(System.in);
System.out.println("Please enter any Sting value as input");
String str=sc.next();
System.out.println("Entered String value is "+str);
}
}

Output:

Please enter any String value as input
instanceofjava
Entered String value is instanceofjava

Program #3: Write a java example program to read data as an input from the user from console using scanner class with delimiters

package com.scannerjava;
import java.util.Scanner;
public class TakeInputUsingScanner {
/**
* @wesite:www.instanceofJava.com
* @category: Java program to take input from user using scanner
*/
public static void main(String[] args) {
String input = "top 10 java interview questions on scanner class";
Scanner sc = new Scanner(input).useDelimiter("\\s");
System.out.println(sc.next());
System.out.println(sc.nextInt());
System.out.println(sc.next());
System.out.println(sc.next());
System.out.println(sc.next());
System.out.println(sc.next());
System.out.println(sc.next());
System.out.println(sc.next());
}
}

Output:

top
10
java
interview
questions
on
scanner
class

Program #4: Write a java example program to read all type of data as an input from the user from console using scanner class

package com.scannerjava;
import java.util.Scanner;
public class TakeInputUsingScanner {
/**
* @wesite:www.instanceofJava.com
* @category: Java program to take input from user using scanner
*/
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.println("Enter an integer value");
System.out.println(sc.nextInt());
System.out.println("Enter a float value");
System.out.println(sc.nextFloat());
System.out.println("Enter a Double value");
System.out.println(sc.nextDouble());
System.out.println("Enter a Byte value");
System.out.println(sc.nextByte());
System.out.println("Enter a Long value");
System.out.println(sc.nextLong());
}
}

Output:

Enter an integer value
12
12
Enter a float value
12.34
12.34
Enter a Double value
12.3456789
12.3456789
Enter a Byte value
2
2
Enter a Long value
9876636363536
9876636363536

Program #5: Write a java example program how to read input from console in java eclipse all type of data as an input from the user from console using scanner class.

Quicksort algorithm in java with example program

Posted by: Instanceofjava Posted date: August 16, 2016 / comment : 1 Core java Interview Questions , java programming interview questions , java sorting algorithms

Quick sort uses divide and conquer algorithm.
First will be divided in to two parts based on some pivot element. All elements which are less than pivot element will be placed left and and all elements which are greater than pivot will be in right part.

So now pivot element is exactly in middle. if we sort left and right side elements all elements will be sorted. Here recursive quick sort will take place in order to sort all elements.
Quick sort will be sorting these elements without using extra space that is the reason it is called in place sorting algorithm.
Using the first or middle elements as an pivot element. it splits the arrays by re arranging the elements like every thing that is less than pivot will come left side and all elements greater than or equal to pivot will come right side.
Now pivot is in middle and correct place it left and right arrays sorted then entire array will be sorted.
Quick sort exactly will do the same it will sort left and right recursively.
If size of input is very less merge sort will be time consuming.
For smaller inputs quick sort is faster than merge sort.
Time complexity of Quicksort default case is O(n log n).
Worst case Time complexity of Quicksort is O(n²).

Steps to implement quick sort algorithm:

Create a array with some elements. Choose pivot element as middle element. we can choose first or last also.
After choosing pivot element arrange the elements like all elements which are less than pivot value comes left side and elements greater than equal to pivot come right side of pivot.
And then apply same to both sides. until it becomes one. then all elements in array will be sorted.

Program #1: Java Example program to sort elements of array using quick sort algorithm:

package quicksortjava;
public class QuickSort {
private int array[];
private int length;
public void sortElements(int[] arrayvalues) {
if (arrayvalues == null || arrayvalues.length == 0) {
return;
}
this.array = arrayvalues;
length = arrayvalues.length;
doQuickSort(0, length - 1);
}
private void doQuickSort(int lowIndex, int highIndex) {
int i = lowIndex;
int j = highIndex;
int pivot = array[lowIndex+(highIndex-lowIndex)/2];
// now Divide the array into two arrays(actually we are maintaining single array only)
while (i <= j) {
while (array[i] < pivot) {
i++;
}
while (array[j] > pivot) {
j--;
}
if (i <= j) {
swapElements(i, j);
//move index to next position on both sides
i++;
j--;
}
}
// call quickSort() method recursively
if (lowIndex < j){
doQuickSort(lowIndex, j);
}
if (i < highIndex){
doQuickSort(i, highIndex);
}
}
private void swapElements(int i, int j) {
int temp = array[i];
array[i] = array[j];
array[j] = temp;
}
public static void main(String a[]){
QuickSort quicksort = new QuickSort();
int[] inputarray = {32,1,23,14,43,7,6,65};
System.out.println("Before sorting");
for(int i:inputarray){
System.out.print(i);
System.out.print(" ");
}
quicksort.sortElements(inputarray);
System.out.println("After sorting");
for(int i:inputarray){
System.out.print(i);
System.out.print(" ");
}
}
}

Output:

Before sorting
32 1 23 14 43 7 6 65
After sorting
1 6 7 14 23 32 43 65

Execution flow explanation of quick sort algorithm

quick sort program in java using recursion program

Creating array of objects in java example program

Posted by: Instanceofjava Posted date: August 15, 2016 / comment : 0 Core java Interview Questions , java programming interview questions , Java Programs

Array is collection of similar data types.
Arrays can hold collection of data with indexes
We already know that we can hold group of primitive variables
Arrays can hold referenced variables also like Strings and objects
So we can say it is possible to store or create array of objects in java

Declaring arrays in java:

One dimensional array can be created like
int[] singlearray;
Two dimensional array can be created like
int[][] intdoubleArray;
double[][] doubleArray;

Instantiation and Initialization of Arrays

Program #1: Java example program to store string object in array

package arraysofobjectsinjava;
public class ArrayOfObjects {
/**
* @www.instanceofjava.com
* creating and assigning values to arrays in java
*/
public static void main(String[] args) {
int[] a= new int[2];
a[0]=1;
a[1]=2;
System.out.println(a[0]);
System.out.println(a[1]);
int[] var= {1,2,3,4,5};
for (int i = 0; i < var.length; i++) {
System.out.println(var[i]);
}
int[][] array=new int[2][2];
array[0][0]=1;
array[0][1]=2;
array[1][0]=3;
array[1][1]=4;
for(int i=0; i<array.length; i++) {
for(int j=0; j<array[1].length; j++)
System.out.print(array[i][j] + " ");
System.out.println();
}
}
}

Output:

Array of objects in java:

Program #2: Java example program to store string object in array

package arraysofobjectsinjava;
public class ArrayofStringObjects {
/**
* @www.instanceofjava.com
* Storing String objects in String array
*/
public static void main(String[] args) {
String a[]= new String[5];
a[0]="array of objects";
a[1]="object array in java";
a[2]="array of objects in java example program";
a[3]="array of objects in java tutorial";
a[4]="how to make array of objects in java";
for (int i = 0; i < a.length; i++) {
System.out.println(a[i]);
}
}
}

Output:

array of objects
object array in java
array of objects in java example program
array of objects in java tutorial
how to make array of objects in java

Creating custom array of objects in java

We can also store custom objects in arrays .
Create a employee class.
Create multiple objects of employee class and assign employee objects to array.
Arrays can store objects but we need to instantiate each and every object and array can store it

Program#3: java example program to create custom objects and store in array

Employee.java

package arraysofobjectsinjava;
public class Employee {
String name;
int id;
Employee(String name, int id){
this.name=name;
this.id=id;
}
}

Tower of hanoi recursive solution using Java

Posted by: Instanceofjava Posted date: August 15, 2016 / comment : 0 Core java Interview Questions , java programming interview questions , Java Programs

Towers of Hanoi is a famous game.
In this game there are three poles and N number of disks placed one over another in increasing in size from top to bottom.

Objective of this game is to move disks from first pole to last pole.
And the condition is we can not place bigger disk on top of smaller disk.
Initially all disks placed in first pole smaller disk will be on top and bigger disk will be on bottom.
We need to move all the disks from from first pole to last pole.

Rules of tower of Hanoi:

We can move only one disk at a time.
At any poi of time larger disk can not be placed on smaller disk.

In order to solve this problem we have given a second pole so we can use second pole and move disks from first pole to third pole.
We can solve this using rec recursive procedure.

Tower of Hanoi with Single disk: N=1

Three poles are A , B ,C
And a disk is present at A we need to move from A to C
As it its single disk we can directly move disk A - > C

Tower of Hanoi with Two disks : N=2

Three poles are A , B ,C
And two disks are placed in pole A, Disk 1 and Disk2 top to bottom.( assume Disk 2 is smaller and Disk 1 bigger)
Move Disk2 from A to B
Move Disk1 From A to C.
Move Disk2 from B to C.

tower of hanoi in data structure program

Tower of Hanoi with Three disks : N=3

Three poles are A , B ,C
And three disks are placed in pole A, Disk 1 top to bot, Disk2 and Disk 2 top bottom to .( assume Disk 3 is smaller and Disk 1 bigger)
In this firs we need to move two disk from A to B which we already done in above procedure
So we need to repeat that here.
Move Disk1 from A to C.
Now Moving two disks from B to C we have already seen in above procedure so its recursive.

Tower of Hanoi Recursive Algorithm:

N = number of disks

If N == 1

Move Single disk from A to C

If N >1

1.Move n-1 disks from start A to B TowersofHanoi(n-1,start, end , aux)
Move last Disk from A to C
Move n-1 disks from B to C. TowersofHanoi(n-1,start, aux, end )

Step 1 and 3 are recursive procedures.
Lets see hoe to write java recursive program for this towers of Hanoi problem
Here B as auxiliary pole.

Program #1: Java Example program on towers of Hanoi:

package towersofhanoi;
import java.util.Scanner;
public class TowersofHanoi {
public void TOH(int n, String start, String aux, String end) {
if (n == 1) {
System.out.println(start + " -> " + end);
} else {
TOH(n - 1, start, end, aux);
System.out.println(start + " -> " + end);
TOH(n - 1, aux, start, end);
}
}
public static void main(String[] args) {
TowersofHanoi towersOfHanoi = new TowersofHanoi();
System.out.print("Enter number of discs: ");
Scanner scanner = new Scanner(System.in);
int discs = scanner.nextInt();
towersOfHanoi.TOH(discs, "A", "B", "C");
}
}

Output:

Enter number of discs:
3
A -> C
A -> B
C -> B
A -> C
B -> A
B -> C
A -> C

8 different ways to convert int to String in java

Posted by: Instanceofjava Posted date: August 14, 2016 / comment : 0 Core java Interview Questions , java programming interview questions

How to convert string to int or integer to string in java?
When we are working on a project we will be having some scenarios of expecting a string from int or integer from string.
Now we will be discussing on how to convert Integer to String in java with example java programs.

8 different ways to convert int to String in java

1.Convert Integer to String using Integer.toString() method:
2.Convert Integer to String using String.valueOf() method.
3.Convert Integer to String / int to String using new Integer(int).toString()
4.Convert Integer to String / int to String using String.format() method
5.Convert Integer to String / int to String using DecimalFormat
6.Convert Integer to String/ int to String using StringBuffer / StringBuilder
7.Convert Integer to String / int to String directly by adding to ""
8.Convert Integer to String / int to String using Special radix.

1.Convert Integer to String using Integer.toString() method:

Integer is a wrapper class in java which is mainly used to represent or convert primitive int value to object.
And Integer class having some predefined methods.
Integer class has special predefined method to convert integer value to string toString();
toString is a static method in Integer class so that by using class name itself we can call that method to convert Integer to corresponding string value.

Program #1: Java Example program to convert Integer to String by using toString() method:

Output:

package convertintegertostring.java;
public class IntegerToString {
/**
* @ website: www.InstanceOfJava.com
*/
public static void main(String[] args) {
Integer i = new Integer(64);
//converting integer to string by calling toString() method on integer object
String str= i.toString();
// also we can use like String str= Integer.toString(i);
System.out.println(str);
}
}

Output:

2.Convert Integer to String using String.valueOf() method.

Integer class have toString() method to convert integer to string value same way String class also has valueOf() method to convert int or integer to string.
String class has a static method valueOf() which takes int as argument and converts into string.

Program #2: Java Example program to convert int to string using valueOf() method.

package convertintegertostring.java;
public class IntegerToString {
/**
* @ website: www.InstanceOfJava.com
*/
public static void main(String[] args) {
Integer i = new Integer(64);
//converting integer to string by calling valueOf() method on String clas
String str= String.valueOf(i);
System.out.println(str);
int number=123;
String numberstr= String.valueOf(number);
System.out.println(numberstr);
}
}

Output:

3.Convert Integer / int to String using new Integer(int).toString()

And here by creating Integer object and directly calling tostring method.
We can convert into to string directly with one statement this will be done by using Integer(int).toString()

Program #3: Java Example program to convert int to string using new Integer(int ).toString()

package convertintegertostring.java;
public class IntegerToString {
/**
* @ website: www.InstanceOfJava.com
*/
public static void main(String[] args) {
int number=23;
String numberstr= new Integer(number).toString();
System.out.println(numberstr);
}
}

Output:

4.Convert Integer / int to String using String.format() method

Another alternative way to convert int t string is by calling String.format method.
String.format ("%d", number);

Program #4: Java Example program to convert int to string using String.format() method

package convertintegertostring.java;
public class IntegerToString {
/**
* @ website: www.InstanceOfJava.com
*/
public static void main(String[] args) {
int number=23;
String numberstr= String.format ("%d", number);
System.out.println(numberstr);
}
}

Output:

5.Convert Integer / int to String using DecimalFormat

Another alternative way to convert int t string is by java.text.DecimalFormat
DecimalFormat class mainly used to represent numbers in formats.
Decimal format class providing format() method to convert int to string with specified format.

Program #5: Java Example program to convert int to string using DecimalFormat class

package convertintegertostring.java;
public class IntegerToString {
/**
* @ website: www.InstanceOfJava.com
*/
public static void main(String[] args) {
int number=23;
DecimalFormat obj= new DecimalFormat("#");
String numberstr= obj.format(number);
System.out.println(numberstr);
DecimalFormat objct= new DecimalFormat("#,###");
String numberstr1= objct.format(3400);
System.out.println(numberstr1);
}
}

Output:

23
3,400

6.Convert Integer / int to String using StringBuffer / StringBuilder

StringBuffer and StringBuilder classes also providing toString() method to convert int to string

Program #6: Java Example program to convert int to string using StringBuffer and StringBuilder

package convertintegertostring.java;
public class IntegerToString {
/**
* @ website: www.InstanceOfJava.com
*/
public static void main(String[] args) {
int number=234;
StringBuffer sf=new StringBuffer();
sf.append(number);
String numberstr= sf.toString();
System.out.println(numberstr);
StringBuilder sb=new StringBuilder();
sb.append(number);
String nstr= sb.toString();
System.out.println(nstr);
}
}

Output:

7.Convert Integer / int to String directly by adding to ""

We can convert a number to string simply by concatenating to "".
But it is not recommended to use.

Program #7: Java Example program to convert int to string by concat to ""

package convertintegertostring.java;
public class IntegerToString {
/**
* @ website: www.InstanceOfJava.com
*/
public static void main(String[] args) {
int number=8538;
String numberstr= ""+number;
System.out.println(numberstr);
}
}

Output:

8538

8.Convert Integer / int to String using Special radix.

Program #8: Java Example program to convert int to string using special radix

package convertintegertostring.java;
public class IntegerToString {
/**
* @ website: www.InstanceOfJava.com
*/
public static void main(String[] args) {
int number=536;
String binaryString = Integer.toBinaryString(number);
System.out.println(binaryString);
String octalString = Integer.toOctalString(number);
System.out.println(octalString);
String hexString = Integer.toHexString(number);
System.out.println(hexString);
String customString = Integer.toString(number, 7);
System.out.println(customString);
}
}

Output:

1000011000
1030
218
1364

8 different ways to convert int to string in java

Output:

64
64
536
536
3,400
536
536
1000011000

Shallow copy in java example program

Posted by: Instanceofjava Posted date: August 14, 2016 / comment : 0 Core java Interview Questions , java programming interview questions

We create exact copy of the object using Cloneable in java.
We need to override object class clone() method.
This is also called clone of the object.
So we can create copy of object using two different way
1. Shallow copy
2. Depp copy

Shallow copy / Shallow cloning in java

In Shallow copy object reference will be copied instead of copying whole data of the object.
So the newly created object will be another reference for existing with same data means shallow copy of the object.
Whenever we change data in the original object same changes made to new object also because both are pointing to same object.

Program #1: Java example program to demonstrate shallow copy / shallow cloning

Example:

package com.shallowcopyvsdeppcopy;
public class Example{
int a;
int b;
Example(int a, int b){
this.a=a;
this.b=b;
}
}

Empclone :

package com.shallowcopyvsdeppcopy;
public class Empclone implements Cloneable {
Example e;
int a;
Empclone (int a, Example es){
this.a=a;
this.e=e;
}
public Object clone()throws CloneNotSupportedException{
return super.clone();
}
public static void main(String[] args) {
Empclone a= new Empclone (2, new Example(3,3));
Empclone b=null;
try {
b=(Empclone )a.clone();
} catch (CloneNotSupportedException e) {
e.printStackTrace();
}
System.out.println(a.e.a);
System.out.println(b.e.a);
a.e.a=12;
System.out.println(a.e.a);
System.out.println(b.e.a);
}
}

Output:

Java interview questions to practice

Posted by: Instanceofjava Posted date: July 17, 2016 / comment : 0 Core java Interview Questions , java programming interview questions

We have provided some java interview programming questions for freshers and experienced candidates.
So please try to answer these java interview questions and practice.
If you have any doubt go through the given explanation link you can get the answer for that.
Still if you need any clarifications feel free to contact us. Skype/Gmail: instanceofjava

Program #1: what will happen if we try to interchange modifiers of main method

package interviewprograms.instanceofjava;
public class InterviewProgram {
/**
* @java interview programming questions and answers for freshers and experienced
*/
static public void main(String[] args) {
System.out.println("Hello world");
}
}

Program #2:Do you know about static in java . How static works?

java interview questions for experienced candidates

Program #3:Java Interview question on try catch block in java

package interviewprograms.instanceofjava;
public class InterviewProgram {
/**
* @java interview programming questions and answers for freshers and experienced
*/
public static void main(String[] args) {
try {
System.out.println("I am try block");
} finally {
System.out.println("I am finally block"); }
}
}

Program #4:Java Interview question on what happens when we print object

package interviewprograms.instanceofjava;
public class InterviewProgram {
/**
* @java interview programming questions and answers for freshers and experienced
*/
public static void main(String[] args) {
try {
System.out.println("I am try block");
} finally {
System.out.println("I am finally block"); }
}
}

Subscribe to: Comments ( Atom )