Java Program to Display All Prime Numbers from 1 to N

In this article, we will understand how to display all the prime numbers from 1 to N in Java. All possible positive numbers from 1 to infinity are called natural numbers. Prime numbers are special numbers who have only two factors 1 and itself and cannot be divided by any other number.

A number is a prime number if its only factors are 1 and itself. 11 is a prime number. Its factors are 1 and 11 itself. Some examples of prime numbers are 2, 3, 5, 7, 11, 13 and so on. 2 is the only even prime number. All other prime numbers are odd numbers.

Below is a demonstration of the same −

Input

Suppose our input is −

Enter the value of n :10

Output

The desired output would be −

2 3 5 7

Algorithm

Step1- Start
Step 2- Declare an integer : n
Step 3- Prompt the user to enter an integer value/ Hardcode the integer
Step 4- Read the values
Step 5- Using a while loop from 1 to n, check if the 'i' value is divisible by any number from 2 to i.
Step 6- If yes, check the next number
Step 7- If no, store the number as a prime number
Step 8- Display the 'i' value as LCM of the two numbers
Step 9- Stop

Example 1

Here, the input is being entered by the user based on a prompt. You can try this example live in ourcoding ground tool .

import java.util.Scanner;
public class PrimeNumbers{
   public static void main(String arg[]){
      int i,n,counter, j;
      Scanner scanner = new Scanner(System.in);
      System.out.println("Required packages have been imported");
      System.out.println("A reader object has been defined ");
      System.out.print("Enter the n value : ");
      n=scanner.nextInt();
      System.out.print("Prime numbers between 1 to 10 are ");
      for(j=2;j<=n;j++){
         counter=0;
         for(i=1;i<=j;i++){
            if(j%i==0){
               counter++;
            }
         }
         if(counter==2)
         System.out.print(j+" ");
      }
   }
}

Output

Required packages have been imported
A reader object has been defined
Enter the n value : 10
Prime numbers between 1 to 10 are 2 3 5 7

Example 2

Here, the integer has been previously defined, and its value is accessed and displayed on the console.

public class PrimeNumbers{
   public static void main(String arg[]){
      int i,n,counter, j;
      n= 10;
      System.out.printf("Enter the n value is %d ", n);
      System.out.printf("\nPrime numbers between 1 to %d are ", n);
      for(j=2;j<=n;j++){
         counter=0;
         for(i=1;i<=j;i++){
            if(j%i==0){
               counter++;
            }
         }
         if(counter==2)
         System.out.print(j+" ");
      }
   }
}

Output

Enter the n value is 10
Prime numbers between 1 to 10 are 2 3 5 7