Java – List All Prime Numbers Between 1 to N

Write a Java program to find all prime number between 1 to N. Where N is a number entered by the user at runtime.

Before writing this program you must know What is a prime number? and how to check if a number is prime or not.

import java.util.Scanner;

public class PrimeNumber1ToN {

    private static Scanner scanner = new Scanner( System.in );

    public static void main(String[] args) {

        System.out.println("Enter max number: ");

        String input = scanner.nextLine();
        int maxNumber = Integer.parseInt( input );

        System.out.println("List of the prime number between 1 - " + maxNumber);

        for (int num = 2; num <= maxNumber; num++)
        {
            boolean isPrime = true;
            for (int i=2; i <= num/2; i++)
            {
                if ( num % i == 0)
                {
                    isPrime = false;
                    break;
                }
            }
			
            if ( isPrime == true )
                System.out.println(num);
        }
    }
}

import java.util.Scanner;

public class PrimeNumber1ToN {

private static Scanner scanner = new Scanner( System.in );

public static void main(String[] args) {

System.out.println("Enter max number: ");

String input = scanner.nextLine();

int maxNumber = Integer.parseInt( input );

System.out.println("List of the prime number between 1 - " + maxNumber);

for (int num = 2; num <= maxNumber; num++)

{

boolean isPrime = true;

for (int i=2; i <= num/2; i++)

{

if ( num % i == 0)

{

isPrime = false;

break;

}

if ( isPrime == true )

System.out.println(num);

}

Compile and run the program

javac PrimeNumber1ToN.java
java PrimeNumber1ToN

Output:

Enter max number:
100
List of the prime number between 1 - 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