{"id":1168,"date":"2022-02-24T19:26:08","date_gmt":"2022-02-24T19:26:08","guid":{"rendered":"https:\/\/mdr.foobrdigital.com\/?p=1168"},"modified":"2022-02-24T19:26:08","modified_gmt":"2022-02-24T19:26:08","slug":"while-and-do-while-loop","status":"publish","type":"post","link":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/2022\/02\/24\/while-and-do-while-loop\/","title":{"rendered":"while and do…while Loop"},"content":{"rendered":"\n

In this tutorial, we will learn how to use while and do while loop in Java with the help of examples.<\/p>\n\n\n\n

In computer programming, loops are used to repeat a block of code. For example, if you want to show a message 100 times, then you can use a loop. It’s just a simple example; you can achieve much more with loops.<\/p>\n\n\n\n

In the previous tutorial, you learned about\u00a0Java for loop. Here, you are going to learn about\u00a0while<\/code>\u00a0and\u00a0do...while<\/code>\u00a0loops.<\/p>\n\n\n\n

\n\n\n\n

Java while loop<\/h2>\n\n\n\n

Java while<\/code> loop is used to run a specific code until a certain condition is met. The syntax of the while<\/code> loop is:<\/p>\n\n\n\n

while (testExpression) {\n    \/\/ body of loop\n}<\/code><\/pre>\n\n\n\n
Here,<\/p>\n\n\n\n
  1. A while<\/code> loop evaluates the textExpression<\/strong> inside the parenthesis ()<\/code>.<\/li>
  2. If the textExpression<\/strong> evaluates to true<\/code>, the code inside the while<\/code> loop is executed.<\/li>
  3. The textExpression<\/strong> is evaluated again.<\/li>
  4. This process continues until the textExpression<\/strong> is false<\/code>.<\/li>
  5. When the textExpression<\/strong> evaluates to false<\/code>, the loop stops.<\/li><\/ol>\n\n\n\n
    <\/p>\n\n\n\n
    \n\n\n\n
    Flowchart of while loop<\/h2>\n\n\n\n
    \"Flowchart
    Flowchart of Java while loop<\/figcaption><\/figure>\n\n\n\n
    \n\n\n\n
    Example 1: Display Numbers from 1 to 5<\/h3>\n\n\n\n
    \/\/ Program to display numbers from 1 to 5\n\nclass Main {\n  public static void main(String[] args) {\n\n    \/\/ declare variables\n    int i = 1, n = 5;\n\n    \/\/ while loop from 1 to 5\n    while(i <= n) {\n      System.out.println(i);\n      i++;\n    }\n  }\n}<\/code><\/pre>\n\n\n\n
    Output<\/strong><\/p>\n\n\n\n
    1\n2\n3\n4\n5<\/samp><\/code><\/pre>\n\n\n\n
    Here is how this program works.<\/p>\n\n\n\n
    Iteration<\/th>Variable<\/th>Condition: i <= n<\/th>Action<\/th><\/tr><\/thead>
    1st<\/td>i = 1<\/code>
    n = 5<\/code><\/td>    		true<\/code><\/td>1<\/samp> is printed.
    i<\/var> is increased to 2<\/strong>.<\/td><\/tr>
    2nd<\/td>i = 2<\/code>
    n = 5<\/code><\/td>    		true<\/code><\/td>2<\/samp> is printed.
    i<\/var> is increased to 3<\/strong>.<\/td><\/tr>
    3rd<\/td>i = 3<\/code>
    n = 5<\/code><\/td>    		true<\/code><\/td>3<\/samp> is printed.
    i<\/var> is increased to 4<\/strong>.<\/td><\/tr>
    4th<\/td>i = 4<\/code>
    n = 5<\/code><\/td>    		true<\/code><\/td>4<\/samp> is printed.
    i<\/var> is increased to 5<\/strong>.<\/td><\/tr>
    5th<\/td>i = 5<\/code>
    n = 5<\/code><\/td>    		true<\/code><\/td>5<\/samp> is printed.
    i<\/var> is increased to 6<\/strong>.<\/td><\/tr>
    6th<\/td>i = 6<\/code>
    n = 5<\/code><\/td>    		false<\/code><\/td>The loop is terminated<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
    \n\n\n\n
    Example 2: Sum of Positive Numbers Only<\/h3>\n\n\n\n
    \/\/ Java program to find the sum of positive numbers\nimport java.util.Scanner;\n\nclass Main {\n  public static void main(String[] args) {\n      \n    int sum = 0;\n\n    \/\/ create an object of Scanner class\n    Scanner input = new Scanner(System.in);\n\n    \/\/ take integer input from the user\n    System.out.println(\"Enter a number\");\n    int number = input.nextInt();\n\t   \n    \/\/ while loop continues \n    \/\/ until entered number is positive\n    while (number >= 0) {\n      \/\/ add only positive numbers\n      sum += number;\n\n      System.out.println(\"Enter a number\");\n      number = input.nextInt();\n    }\n\t   \n    System.out.println(\"Sum = \" + sum);\n    input.close();\n  }\n}<\/code><\/pre>\n\n\n\n
    Output<\/strong><\/p>\n\n\n\n
    Enter a number\n25\nEnter a number\n9\nEnter a number\n5\nEnter a number\n-3\nSum = 39<\/samp><\/code><\/pre>\n\n\n\n
    In the above program, we have used the\u00a0Scanner class\u00a0to take input from the user. Here,\u00a0nextInt()<\/code>\u00a0takes integer input from the user.<\/p>\n\n\n\n
    The while<\/code> loop continues until the user enters a negative number. During each iteration, the number entered by the user is added to the sum<\/code> variable.<\/p>\n\n\n\n
    When the user enters a negative number, the loop terminates. Finally, the total sum is displayed.<\/p>\n\n\n\n
    \n\n\n\n
    Java do…while loop<\/h2>\n\n\n\n
    The do...while<\/code> loop is similar to while loop. However, the body of do...while<\/code> loop is executed once before the test expression is checked. For example,<\/p>\n\n\n\n
    do {\n    \/\/ body of loop\n} while(textExpression);<\/code><\/pre>\n\n\n\n
    Here,<\/p>\n\n\n\n
    1. The body of the loop is executed at first. Then the textExpression<\/strong> is evaluated.<\/li>
    2. If the textExpression<\/strong> evaluates to true<\/code>, the body of the loop inside the do<\/code> statement is executed again.<\/li>
    3. The textExpression<\/strong> is evaluated once again.<\/li>
    4. If the textExpression<\/strong> evaluates to true<\/code>, the body of the loop inside the do<\/code> statement is executed again.<\/li>
    5. This process continues until the textExpression<\/strong> evaluates to false<\/code>. Then the loop stops.<\/li><\/ol>\n\n\n\n
      \n\n\n\n
      Flowchart of do…while loop<\/h3>\n\n\n\n
      \"Flowchart
      Flowchart of Java do while loop<\/figcaption><\/figure>\n\n\n\n
      \n\n\n\n
      Let’s see the working of do...while<\/code> loop.<\/p>\n\n\n\n
      Example 3: Display Numbers from 1 to 5<\/h3>\n\n\n\n
      \/\/ Java Program to display numbers from 1 to 5\n\nimport java.util.Scanner;\n\n\/\/ Program to find the sum of natural numbers from 1 to 100.\n\nclass Main {\n  public static void main(String[] args) {\n\n    int i = 1, n = 5;\n\n    \/\/ do...while loop from 1 to 5\n    do {\n      System.out.println(i);\n      i++;\n    } while(i <= n);\n  }\n}<\/code><\/pre>\n\n\n\n
      Output<\/strong><\/p>\n\n\n\n
      1\n2\n3\n4\n5<\/samp><\/code><\/pre>\n\n\n\n
      Here is how this program works.<\/p>\n\n\n\n
      Iteration<\/th>Variable<\/th>Condition: i <= n<\/th>Action<\/th><\/tr><\/thead>
       <\/td>i = 1<\/code>
      n = 5<\/code><\/td>      		not checked<\/td>1<\/samp> is printed.
      i<\/var> is increased to 2<\/strong>.<\/td><\/tr>
      1st<\/td>i = 2<\/code>
      n = 5<\/code><\/td>      		true<\/code><\/td>2<\/samp> is printed.
      i<\/var> is increased to 3<\/strong>.<\/td><\/tr>
      2nd<\/td>i = 3<\/code>
      n = 5<\/code><\/td>      		true<\/code><\/td>3<\/samp> is printed.
      i<\/var> is increased to 4<\/strong>.<\/td><\/tr>
      3rd<\/td>i = 4<\/code>
      n = 5<\/code><\/td>      		true<\/code><\/td>4<\/samp> is printed.
      i<\/var> is increased to 5<\/strong>.<\/td><\/tr>
      4th<\/td>i = 5<\/code>
      n = 5<\/code><\/td>      		true<\/code><\/td>6<\/samp> is printed.
      i<\/var> is increased to 6<\/strong>.<\/td><\/tr>
      5th<\/td>i = 6<\/code>
      n = 5<\/code><\/td>      		false<\/code><\/td>The loop is terminated<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
      \n\n\n\n
      Example 4: Sum of Positive Numbers<\/h3>\n\n\n\n
      \/\/ Java program to find the sum of positive numbers\nimport java.util.Scanner;\n\nclass Main {\n  public static void main(String[] args) {\n      \n    int sum = 0;\n    int number = 0;\n\n    \/\/ create an object of Scanner class\n    Scanner input = new Scanner(System.in);\n\t   \n    \/\/ do...while loop continues \n    \/\/ until entered number is positive\n    do {\n      \/\/ add only positive numbers\n      sum += number;\n      System.out.println(\"Enter a number\");\n      number = input.nextInt();\n    } while(number >= 0); \n\t   \n    System.out.println(\"Sum = \" + sum);\n    input.close();\n  }\n}<\/code><\/pre>\n\n\n\n
      Output 1<\/strong><\/p>\n\n\n\n
      Enter a number\n25\nEnter a number\n9\nEnter a number\n5\nEnter a number\n-3\nSum = 39<\/samp><\/code><\/pre>\n\n\n\n
      Here, the user enters a positive number, that number is added to the sum<\/var> variable. And this process continues until the number is negative. When the number is negative, the loop terminates and displays the sum without adding the negative number.<\/p>\n\n\n\n
      Output 2<\/strong><\/p>\n\n\n\n
      Enter a number\n-8\nSum is 0<\/samp><\/code><\/pre>\n\n\n\n
      Here, the user enters a negative number. The test condition will be false<\/code> but the code inside of the loop executes once.<\/p>\n\n\n\n
      \n\n\n\n
      Infinite while loop<\/h3>\n\n\n\n
      If the condition<\/strong> of a loop is always true<\/code>, the loop runs for infinite times (until the memory is full). For example,<\/p>\n\n\n\n
      \/\/ infinite while loop\nwhile(true){\n    \/\/ body of loop\n}<\/code><\/pre>\n\n\n\n
      Here is an example of an infinite do...while<\/code> loop.<\/p>\n\n\n\n
      \/\/ infinite do...while loop\nint count = 1;\ndo {\n   \/\/ body of loop\n} while(count == 1)<\/code><\/pre>\n\n\n\n
      In the above programs, the textExpression<\/strong> is always true<\/code>. Hence, the loop body will run for infinite times.<\/p>\n\n\n\n
      \n\n\n\n
      for and while loops<\/h2>\n\n\n\n
      The for<\/code> loop is used when the number of iterations is known. For example,<\/p>\n\n\n\n
      for (let i = 1; i <=5; ++i) {\n   \/\/ body of loop\n}<\/code><\/pre>\n\n\n\n
      And while<\/code> and do...while<\/code> loops are generally used when the number of iterations is unknown. For example,<\/p>\n\n\n\n
      while (condition) {\n    \/\/ body of loop\n}<\/code><\/pre>\n","protected":false},"excerpt":{"rendered":"
      In this tutorial, we will learn how to use while and do while loop in Java with the help of examples. In computer programming, loops are used to repeat a block of code. For example, if you want to show a message 100 times, then you can use a loop. It’s just a simple example; […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[363],"tags":[],"_links":{"self":[{"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/posts\/1168"}],"collection":[{"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/comments?post=1168"}],"version-history":[{"count":0,"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/posts\/1168\/revisions"}],"wp:attachment":[{"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/media?parent=1168"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/categories?post=1168"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/tags?post=1168"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}