In Previous post Check whether a number is prime or not we learnt how to check whether given number is prime number or not and this post is all about Java Program to displaying prime numbers
As we know that a number is a prime number if it is a natural number greater than 1 and it can be divided either by 1 or by the number itself. As example- 2, 3, 5, 7, 11, 13, 17,19,23..….
For checking if a number is prime or not you have to run a loop starting from 2 till number/2 to check if number has any divisor or not.
As example – If number is 10 then you just need to check till 5 (10/2) to see if it divides by any number or not. Same way if you have a number 25 you just need to check till 12(25/2) to see if it divides completely by any number or not. We’ll use the same concept/logic to write our java program to check for prime number.
Note: You should note that 0 and 1 are not prime numbers. We have number 2 is the only even prime number because all the other even numbers can be divided by 2.
Let’s write a Java Program to displaying prime numbers
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package com.kkjavatutorials.clients; import java.util.Scanner; /** * * @author KK JavaTutorials *Java Program to displaying prime numbers */ public class DisplayPrimeNumbersTest { public static void main(String[] args) { Scanner scanner = null; try { // Taking input from the user using scanner scanner = new Scanner(System.in); System.out.println("Please enter number till which you want prime numbers to be printed:"); int number = scanner.nextInt(); if(number<=1){ System.out.println("Enter valid number"); return; } for (int i = 2; i <=number; i++) { if(isPrimeNumber(i)){ System.out.print(i+" "); } } } catch (Exception e) { e.printStackTrace(); } finally { if (scanner != null) scanner.close(); } } private static boolean isPrimeNumber(int number) { boolean flag = true; // for loop start from 2 and increment it till number/2 for (int i = 2; i <=number/2; i++) { // if no remainder found means we get divider if (number % i == 0) { flag = false; break; } } return flag; } } |
Output of this program:
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Please enter number till which you want prime numbers to be printed: 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 |
That’s all about Java Program to displaying prime numbers
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