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Java Program to Check Prime Number or Not
This article is created to cover a program in Java that checks whether a number entered by the user is a prime number or not. I've used the following two ways to do the job:
- Using the for loop, check the prime number.
- Using the while loop, check the prime number.
Note: A prime number is a number that can only be divisible by 1 and the number itself. For example, 2, 3, 5, 7, 11, etc.
Check Prime Number in Java using for Loop
The question is, should I write a Java program to check the prime number or not use a for loop? The user must receive the number during program execution. The program given below is its answer:
import java.util.Scanner; public class fresherearth { public static void main(String[] args) { int num, i, count=0; Scanner s = new Scanner(System.in); System.out.print("Enter a Number: "); num = s.nextInt(); for(i=2; i<num; i++) { if(num%i == 0) { count++; break; } } if(count==0) System.out.println("\nIt is a Prime Number."); else System.out.println("\nIt is not a Prime Number."); } }
The snapshot given below shows the sample run of the above Java program with user input at 19:
Since the number 19 can only be divisible by 1 and the number itself (19) without leaving any remainder, therefore, 19 is a prime number.
Check Prime Number in Java using while Loop
This program is created using the while loop. Also, the program is modified in a way that it will print the number along with a message saying whether it is prime or not. Let's have a look at the program given below:
import java.util.Scanner; public class fresherearth { public static void main(String[] args) { int num, i=2, count=0; Scanner s = new Scanner(System.in); System.out.print("Enter a Number: "); num = s.nextInt(); while(i<num) { if(num%i == 0) { count++; break; } i++; } if(count==0) System.out.println("\n" +num+ " is a Prime Number."); else System.out.println("\n" +num+ " is not a Prime Number."); } }
Here is its sample run with user input, 12:
12 is not a prime number because, except for 1, the numbers 2, 3, 4, and 6 also divide 12.
Same Program in Other Languages
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