Program to Print Prime Number From 1 to 100 in Java

Details

What is a Prime Number?

A Prime Number is a number that is only divisible by one or itself. It is a natural number greater than one that is not a product of two smaller natural numbers. For example, 11 is only divisible by one or itself. Other Prime numbers 2, 3, 5, 7, 11, 13, 17, etc.

Note: 0 and 1 are not prime numbers. 2 is the only even prime number.

How to Print Prime Numbers Between 1 to 100 Program in Java

Below is the Java program to print prime numbers from 1 to 100:

Program Logic:

  • The main method of prime number program in Java contains a loop to check prime numbers between 1 to 100 in Java one by one.
  • The main method calls the method CheckPrime to determine whether a number is prime number in Java or not.
  • We need to divide an input number, say 17 from values 2 to 17 and check the remainder. If the remainder is 0 number is not prime.
  • No number is divisible by more than half of itself. So, we need to loop through just numberToCheck/2. If the input is 17, half is 8.5, and the loop will iterate through values 2 to 8
  • If numberToCheck is entirely divisible by another number, we return false, and loop is broken.
  • If numberToCheck is prime, we return true.
  • In the main method for prime numbers 1 to 100 in Java, check isPrime is TRUE and add to primeNumbersFound String
  • Lastly, print prime numbers from 1 to 100 in Java
    • public class primeNumbersFoundber {

    public static void main(String[] args) {

        int i;
        int num = 0;
        int maxCheck = 100; // maxCheck limit till which you want to find prime numbers
        boolean isPrime = true;

        //Empty String
        String primeNumbersFound = "";

        //Start loop 2 to maxCheck
        for (i = 2; i <= maxCheck; i++) {
            isPrime = CheckPrime(i);
            if (isPrime) {
                primeNumbersFound = primeNumbersFound + i + " ";
            }
        }
        System.out.println("Prime numbers from 1 to " + maxCheck + " are:");
        // Print prime numbers from 1 to maxCheck
        System.out.println(primeNumbersFound);
    }
    public static boolean CheckPrime(int numberToCheck) {
        int remainder;
        for (int i = 2; i <= numberToCheck / 2; i++) {
            remainder = numberToCheck % i;
            //if remainder is 0 than numberToCheckber is not prime and break loop. Else continue loop
            if (remainder == 0) {
                return false;
            }
        }
        return true;

    }

}

    Output:

    The output of the prime number between 1 to 100 in Java program will be: 

    Prime numbers from 1 to 100 are:
2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97

    Check our program to Find Prime Numbers from Any Input Number