In Java How to Start a Program Over Again

In computer programming, loops are used to repeat a cake of code. For example, if yous desire to show a bulletin 100 times, then you can use a loop. It's just a unproblematic example; yous can reach much more than with loops.

In the previous tutorial, you learned almost Coffee for loop. Here, y'all are going to learn about while and do...while loops.

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Java while loop

Coffee while loop is used to run a specific lawmaking until a certain condition is met. The syntax of the while loop is:

          while (testExpression) {     // body of loop }        

Hither,

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 about the conditions, visit Java relational and logical operators.

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Flowchart of while loop

Flowchart of Coffee while loop

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Instance 1: Brandish Numbers from ane to five

          // Program to display numbers from ane to 5  class Main {   public static void principal(Cord[] args) {      // declare variables     int i = ane, due north = 5;      // while loop from 1 to v     while(i <= n) {       System.out.println(i);       i++;     }   } }        

Output

          ane 2 3 4 v        

Here is how this program works.

Iteration	Variable	Condition: i <= n	Action
1st	i = i n = 5	true	ane is printed. i is increased to 2.
2d	i = 2 n = 5	true	2 is printed. i is increased to 3.
tertiary	i = 3 n = 5	true	iii is printed. i is increased to 4.
fourth	i = 4 n = 5	truthful	4 is printed. i is increased to 5.
5th	i = 5 n = five	true	5 is printed. i is increased to 6.
6th	i = half dozen n = 5	fake	The loop is terminated

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Instance 2: Sum of Positive Numbers Merely

          // 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 course     Scanner input = new Scanner(Organisation.in);      // accept integer input from the user     Arrangement.out.println("Enter a number");     int number = input.nextInt(); 	        // while loop continues      // until entered number is positive     while (number >= 0) {       // add together only positive numbers       sum += number;        System.out.println("Enter a number");       number = input.nextInt();     } 	        System.out.println("Sum = " + sum);     input.close();   } }        

Output

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

In the above program, we accept used the Scanner class 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 exercise...while loop

The do...while loop is similar to while loop. However, the body of do...while loop is executed once before the test expression is checked. For example,

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

Here,

1. The body of the loop is executed at first. And then the textExpression is evaluated.
2. If the textExpression evaluates to true, the body of the loop inside the do statement is executed again.
3. The textExpression is evaluated one time once again.
4. If the textExpression evaluates to true, the body of the loop within the do statement is executed again.
5. This process continues until the textExpression evaluates to simulated. Then the loop stops.

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Flowchart of exercise...while loop

Flowchart of Coffee do while loop

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Let's run into the working of do...while loop.

Case 3: Display Numbers from 1 to 5

          // Java Program to display numbers from 1 to v  import coffee.util.Scanner;  // Program to find the sum of natural numbers from 1 to 100.  class Master {   public static void principal(String[] args) {      int i = 1, n = 5;      // do...while loop from 1 to 5     do {       System.out.println(i);       i++;     } while(i <= n);   } }        

Output

          1 2 3 4 5        

Here is how this program works.

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

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Example 4: Sum of Positive Numbers

          // Java plan to detect the sum of positive numbers import coffee.util.Scanner;  class Principal {   public static void primary(String[] args) {            int sum = 0;     int number = 0;      // create an object of Scanner class     Scanner input = new Scanner(Organisation.in); 	        // practise...while loop continues      // until entered number is positive     exercise {       // add only positive numbers       sum += number;       System.out.println("Enter a number");       number = input.nextInt();     } while(number >= 0);  	        System.out.println("Sum = " + sum);     input.close();   } }        

Output i

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

Here, the user enters a positive number, that number is added to the sum variable. And this process 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 examination condition will be simulated merely the code within of the loop executes once.

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Space while loop

If the condition of a loop is always true, the loop runs for infinite times (until the memory is total). For example,

          // space while loop while(true){     // body of loop }        

Here is an case of an space practice...while loop.

          // infinite do...while loop int count = 1; practice {    // trunk of loop } while(count == 1)        

In the above programs, the textExpression is e'er true. 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 instance,

          for (let i = 1; i <=5; ++i) {    // body of loop }        

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

          while (condition) {     // torso of loop }        

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

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