There are several looping statements available in java. One of them is while loop in java.
While loop is used to execute some statements repeatedly until condition returns false. If number of iterations are not known beforehand, while loop is recommended.
The syntax for while loop in java:
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while(condition){ //block of statements } |
Let’s take a very simple example:
Print number from 1 to 10 using while loop
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public class WhileLoopMain { public static void main(String[] args) { int i=1; while(i<11) { System.out.print(" "+i); i++; } } } |
Output:
If you are still confused with above concept, let’s understand it with the help of flow diagram.
Let’s try to print only even numbers now.
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public class WhileLoopMain { public static void main(String[] args) { int i=1; while(i<11) { if(i%2==0) System.out.print(" "+i); i++; } } } |
Output:
Exercise:
If you are given an array of integer, you need to find an element in that array.
Input:
{32,45,53,65,43,23}
You need to write a program to search an element in the array.If element is found in the array, return “PRESENT” else return “NOT PRESENT”
I would recommend you to try it yourself and then look at below code.
Program:
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package org.arpit.java2blog; public class WhileLoopMain { public static void main(String[] args) { WhileLoopMain bse=new WhileLoopMain(); int arr[] ={32,45,53,65,43,23}; System.out.println(bse.findElementInArr(arr, 53)); } public String findElementInArr(int arr[],int elementTobeFound) { int i=0; while(i<arr.length) { if(arr[i]==elementTobeFound) { System.out.println(elementTobeFound+" is present in the array "); return "PRESENT"; } i++; } return "NOT PRESENT"; } } |
Output:
PRESENT
Infinite for loop:
You need to be careful with condition you provide in for loop otherwise, you may end up creating infinite for loop.
For example:
Let’s say you want to print number from 10 to 1 and you use below code:
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package org.arpit.java2blog; public class WhileLoopMain { public static void main(String[] args) { int i=10; while(i>0) { System.out.print(" "+i); i--; } } } |
Output:
Now in above code, instead of i–, you have put i++. In this code,loop will go into infinite loop.
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package org.arpit.java2blog; public class WhileLoopMain { public static void main(String[] args) { int i=10; while(i>0) { System.out.print(" "+i); i++; } } } |
Another example of infinite while loop in java is below code:
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package org.arpit.java2blog; package org.arpit.java2blog; public class WhileLoopMain { public static void main(String[] args) { while(true) { } } } |
