loops in Java

There are 4 types of looping statements in Java.

  1. for – 2 variations
  2. while
  3. do ….while
  4. foreach method in Java 8 – used to iterate through collection type of class

Do while in Java

For loop in Java

Below example will illustrate looping statements in Java.

package loops;

import java.util.ArrayList;

/**
 * Created by Sagar on 16-04-2016.
 */
public class Loops {

    public static void main(String [] args){
        //for loop
        for(int i=1;i<=3;i++){
            System.out.println("Value of i in for loop -> " + i);
        }

        //another for loop
        ArrayList<String> a = new ArrayList<>();
        a.add("Brisbane");
        a.add("Mumbai");
        a.add("London");

        for(String s : a){
            //Print each element in ArrayList
            System.out.println("In other for loop -> " + s);
        }

        //do loop
        int i = 1;
        do{
            System.out.println("Value of i in do loop -> " + i++);
        }while(i<=4);

        //while loop
        i = 1;
        while(i<=4){
            System.out.println("Value of i in While loop -> " + i++);
        }

        //foreach using lambda expression
        a.forEach((s)->System.out.println("Inside foreach loop -> " + s));

    }
}

Here is the output of above Java example

Value of i in for loop -> 1
Value of i in for loop -> 2
Value of i in for loop -> 3
In other for loop -> Brisbane
In other for loop -> Mumbai
In other for loop -> London
Value of i in do loop -> 1
Value of i in do loop -> 2
Value of i in do loop -> 3
Value of i in do loop -> 4
Value of i in While loop -> 1
Value of i in While loop -> 2
Value of i in While loop -> 3
Value of i in While loop -> 4
Inside foreach loop -> Brisbane
Inside foreach loop -> Mumbai
Inside foreach loop -> London

break and continue keyword in Java

break keyword is used to come out of loop. continue keyword is used to jump to next iteration in a loop. These keywords can be used in for loop, while loop, do…while loop

Below example illustrates the use of break and continue keywords.

package loops;

/**
 * Created by Sagar on 19-04-2016.
 */
public class BreakContinue {


    public static void main(String [] args){

        System.out.println("break keyword");
        //break keyword breaks out of loop and executes next statement
        for (int i=1;i<10;i++){
            if (i==5)
                break;
            System.out.println("value of i is -> " + i);
        }

        System.out.println("continue keyword");
        for (int i=1;i<10;i++){

            //continue keyword takes control to the beginning of loop
            //It does not execute statements that follow
            if (i==5)
                continue;
            System.out.println("value of i is -> " + i);
        }

        int [] a = {1,2,3};
        for(int v:a){
            System.out.println(v);
            break;
        }

    }
}

Here is the output of above example.
break keyword
value of i is -> 1
value of i is -> 2
value of i is -> 3
value of i is -> 4
continue keyword
value of i is -> 1
value of i is -> 2
value of i is -> 3
value of i is -> 4
value of i is -> 6
value of i is -> 7
value of i is -> 8
value of i is -> 9
1

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