This post shows how you can generate and display prime numbers in Java in the given range.
A number is a prime number if can be divided either by 1 or by the number itself. So every number with in the given range has to be divided starting from 2 till number/2 in the loop. You only need to run your loop from 2 to N/2 (where N is the passed number), reason being no number is completely divisible by a number more than its half.
Java code to display prime numbers within the given range
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import java.util.Scanner; public class DisplayPrime { public static void main(String[] args) { Scanner sc = new Scanner(System.in); System.out.println("Enter start number for displaying prime numbers - "); int start = sc.nextInt(); // Since 1 and 0 are not considered prime if(start == 0 || start == 1){ start = 2; } System.out.println("Enter end number for displaying prime numbers - "); int end = sc.nextInt(); for(int i = start; i <= end; i++){ if(isPrimeNumebr(i)){ System.out.print(i + " "); } } } /** * * @param num * @return */ private static boolean isPrimeNumebr(int num){ boolean flag = true; for(int i = 2; i < num/2; i++){ // No remainder means completely divides if(num % i == 0){ flag = false; break; } } return flag; } } |
Output
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Enter start number for displaying prime numbers - 1 Enter end number for displaying prime numbers - 20 2 3 4 5 7 11 13 17 19 Enter start number for displaying prime numbers - 20 Enter end number for displaying prime numbers - 100 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97 |
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