Would You Like to Run the Program Again Java Methods

In computer programming, loops are used to repeat a block of code. For example, if yous want to show a message 100 times, then you can use a loop. It's just a simple example; you can achieve much more than with loops.

In the previous tutorial, you learned about Coffee for loop. Hither, you are going to learn about while and do...while loops.

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Coffee while loop

Java while loop is used to run a specific code until a sure condition is met. The syntax of the while loop is:

          while (testExpression) {     // body of loop }        

Here,

1. A while loop evaluates the textExpression inside the parenthesis ().
2. If the textExpression evaluates to true, the code inside the while loop is executed.
3. The textExpression is evaluated again.
4. This process continues until the textExpression is false.
5. When the textExpression evaluates to false, the loop stops.

To learn more virtually the weather, visit Java relational and logical operators.

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Flowchart of while loop

Flowchart of Java while loop

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Instance i: Display Numbers from 1 to v

          // Program to display numbers from 1 to 5  form Master {   public static void main(String[] args) {      // declare variables     int i = 1, n = 5;      // while loop from 1 to v     while(i <= n) {       System.out.println(i);       i++;     }   } }        

Output

          i 2 three four 5        

Here is how this program works.

Iteration	Variable	Condition: i <= due north	Action
1st	i = i n = v	truthful	1 is printed. i is increased to 2.
2d	i = 2 n = 5	true	2 is printed. i is increased to iii.
3rd	i = 3 n = 5	true	3 is printed. i is increased to 4.
4th	i = 4 n = 5	true	4 is printed. i is increased to five.
5th	i = 5 n = five	true	5 is printed. i is increased to 6.
6th	i = 6 n = 5	false	The loop is terminated

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Example ii: Sum of Positive Numbers Only

          // Java program to find the sum of positive numbers import java.util.Scanner;  class Main {   public static void main(String[] args) {            int sum = 0;      // create an object of Scanner class     Scanner input = new Scanner(Arrangement.in);      // accept integer input from the user     System.out.println("Enter a number");     int number = input.nextInt(); 	        // while loop continues      // until entered number is positive     while (number >= 0) {       // add merely positive numbers       sum += number;        System.out.println("Enter a number");       number = input.nextInt();     } 	        System.out.println("Sum = " + sum);     input.shut();   } }        

Output

          Enter a number 25 Enter a number ix Enter a number 5 Enter a number -3 Sum = 39        

In the above program, we have used the Scanner grade to take input from the user. Hither, nextInt() takes integer input from the user.

The while loop continues until the user enters a negative number. During each iteration, the number entered past the user is added to the sum variable.

When the user enters a negative number, the loop terminates. Finally, the total sum is displayed.

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Java do...while loop

The practise...while loop is similar to while loop. Still, the body of do...while loop is executed once before the examination expression is checked. For case,

          do {     // body of loop } while(textExpression);        

Hither,

1. The body of the loop is executed at first. And so the textExpression is evaluated.
2. If the textExpression evaluates to truthful, the body of the loop inside the do statement is executed again.
3. The textExpression is evaluated in one case once again.
4. If the textExpression evaluates to truthful, the torso of the loop inside the do statement is executed again.
5. This procedure continues until the textExpression evaluates to false. And then the loop stops.

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Flowchart of practise...while loop

Flowchart of Coffee do while loop

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Let'due south run into the working of do...while loop.

Instance iii: Display Numbers from 1 to 5

          // Java Program to brandish numbers from 1 to 5  import coffee.util.Scanner;  // Program to find the sum of natural numbers from 1 to 100.  form Main {   public static void main(String[] args) {      int i = 1, n = five;      // do...while loop from i to 5     exercise {       System.out.println(i);       i++;     } while(i <= north);   } }        

Output

          1 2 3 four 5        

Here is how this programme works.

Iteration	Variable	Condition: i <= n	Action
	i = 1 n = 5	not checked	1 is printed. i is increased to 2.
1st	i = 2 n = 5	truthful	2 is printed. i is increased to three.
2nd	i = 3 northward = 5	true	3 is printed. i is increased to 4.
3rd	i = 4 northward = 5	true	four is printed. i is increased to 5.
4th	i = 5 n = v	truthful	half dozen is printed. i is increased to 6.
5th	i = 6 n = v	false	The loop is terminated

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Example 4: Sum of Positive Numbers

          // Java program to find the sum of positive numbers import java.util.Scanner;  class Primary {   public static void main(String[] args) {            int sum = 0;     int number = 0;      // create an object of Scanner class     Scanner input = new Scanner(System.in); 	        // do...while loop continues      // until entered number is positive     practise {       // add only positive numbers       sum += number;       Organization.out.println("Enter a number");       number = input.nextInt();     } while(number >= 0);  	        Organization.out.println("Sum = " + sum);     input.close();   } }        

Output 1

          Enter a number 25 Enter a number 9 Enter a number 5 Enter a number -3 Sum = 39        

Hither, the user enters a positive number, that number is added to the sum variable. And this procedure continues until the number is negative. When the number is negative, the loop terminates and displays the sum without calculation the negative number.

Output 2

          Enter a number -8 Sum is 0        

Here, the user enters a negative number. The test status volition be false but the code inside of the loop executes once.

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Infinite while loop

If the condition of a loop is e'er true, the loop runs for infinite times (until the retentivity is total). For instance,

          // infinite while loop while(true){     // torso of loop }        

Here is an case of an infinite do...while loop.

          // space do...while loop int count = 1; exercise {    // body of loop } while(count == 1)        

In the above programs, the textExpression is e'er truthful. Hence, the loop trunk will run for infinite times.

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for and while loops

The for loop is used when the number of iterations is known. For case,

          for (permit i = ane; i <=5; ++i) {    // trunk of loop }        

And while and do...while loops are generally used when the number of iterations is unknown. For example,

          while (condition) {     // body of loop }        

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Source: https://www.programiz.com/java-programming/do-while-loop

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