Java program to print prime numbers below 100

Any whole number which is greater than 1 and has only two factors i.e. 1 and the number itself, is called a prime number. Other than these two number it has no positive divisor. In this article, we will explain Java programs to print prime numbers between 1 to 100.

Few examples of prime numbers are ? 2, 3, 5, 7, 11 etc.

Steps to Print Prime numbers below 100

Follow the steps below to print prime numbers below 100 in Java ?

• Take integer variable, let's say "A"
• Divide the variable A with (A-1 to 2)
• If A is not divisible by any value (A-1 to 2), then it is a prime number.
• Repeat this for all the numbers starting from 2 to the required limit.

Example 1

The following Java program prints the prime number below 100.

public class First100Primes {
   public static void main(String args[]){

      for(int i = 2; i<=100;){
         int prime = 1;
         for(int loop = 2; loop <=i; loop++) {
            if((i % loop) == 0 && loop!=i) {
               prime = 0;
            }
         }
         if (prime != 0){
            System.out.println(i +" is a prime number");
            i++;
         }
         else
         i++;
      }
   }
}

Output

2 is a prime number
3 is a prime number
5 is a prime number
7 is a prime number
11 is a prime number
13 is a prime number
17 is a prime number
19 is a prime number
23 is a prime number
29 is a prime number
31 is a prime number
37 is a prime number
41 is a prime number
43 is a prime number
47 is a prime number
53 is a prime number
59 is a prime number
61 is a prime number
67 is a prime number
71 is a prime number
73 is a prime number
79 is a prime number
83 is a prime number
89 is a prime number
97 is a prime number

Example 2

The is another Java program that prints the prime numbers below 100.

public class First100Primes {
   public static void main(String[] args) {
      boolean[] prime = new boolean[100];
      for (int i = 2; i < 100; i++) {
         prime[i] = true;
      }
      // finding non-prime numbers
      for (int i = 2; i * i < 100; i++) {
         if (prime[i]) {
            for (int j = i * i; j < 100; j += i) {
               prime[j] = false;
            }
         }
      }
      System.out.println("Prime numbers below 100: ");
      // printing prime numbers
      for (int i = 2; i < 100; i++) {
         if (prime[i]) {
            System.out.print(i + " ");
         }
      }
   }
}

Output

Prime numbers below 100: 
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