Here is a Java program to print all prime numbers between 1 to 100 using for loop. In this java program, we have to print all prime numbers between 1 to 100. There are various methods of primality testing but here we will use a basic method of repetitive division.

A **Prime number** is a whole number greater than 1 that is only divisible by either 1 or itself. All numbers other than prime numbers are known as composite numbers. Composite numbers will have factors other than 1 or itself. There are infinitely many prime numbers, here is the list of first few prime numbers

2 3 5 7 11 13 17 19 23 29....

**Algorithm to check prime number or not**

Let, N be a positive number.

- For every number i, between 2 to N/2(2<= i <= N/2) check whether i divides N completely(check If i is a factor of N).
- if (N % i == 0), then N cannot be a Prime number.
- If none of the number between 2 to N/2 divides N completely then N is a prime number.

## Java program to print all prime numbers between 1 to 100

In this java program, we iterate from 2 to 100 and for every number "i" we check whether "i" is prime number or not. If it is prime number then we print it on screen otherwise continue.

package com.tcc.java.programs; import java.util.Scanner; public class PrintPrimeNumbers { public static void main(String[] args) { int i, j, isPrime, n; System.out.println("All Prime Numbers Between 1 to 100"); // For every number between 2 to 100, check // whether it is prime number or not for (i = 2; i <= 100; i++) { isPrime = 0; // Check whether i is prime or not for (j = 2; j <= i / 2; j++) { // If any number between 2 to i/2 divides i // completely then i cannot be prime number if (i % j == 0) { isPrime = 1; break; } } if (isPrime == 0) System.out.print(i + " "); } } }Output

All Prime Numbers Between 1 to 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

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