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
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 + " ");
}
}
}
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
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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