Algorithm

  1. Start.
  2. Initialize a variable num with the given number.
  3. If num is less than 2, print "Not Prime" and exit.
  4. Iterate from i equals 2 to the square root of num. a. If num is divisible evenly by i, print "Not Prime" and exit.
  5. If no divisor is found in the loop, print "Prime."
  6. End.

 

Code Examples

#1 Code Example- Program to Check Prime Number using a for loop

Code - Java Programming

public class Main {

  public static void main(String[] args) {

    int num = 29;
    boolean flag = false;
    for (int i = 2; i  < = num / 2; ++i) {
      // condition for nonprime number
      if (num % i == 0) {
        flag = true;
        break;
      }
    }

    if (!flag)
      System.out.println(num + " is a prime number.");
    else
      System.out.println(num + " is not a prime number.");
  }
}
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Output

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–
+
cmd
29 is a prime number.

#2 Code Example- Program to Check Prime Number using a while loop

Code - Java Programming

public class Main {

  public static void main(String[] args) {

    int num = 33, i = 2;
    boolean flag = false;
    while (i  < = num / 2) {
      // condition for nonprime number
      if (num % i == 0) {
        flag = true;
        break;
      }

      ++i;
    }

    if (!flag)
      System.out.println(num + " is a prime number.");
    else
      System.out.println(num + " is not a prime number.");
  }
}
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Output

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+
cmd
33 is not a prime number.
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Demonstration

Java Programing Example to Check Whether a Number is Prime or Not-DevsEnv