判断m-n之间有多少个素数，并输出所有素数。

import java.util.Scanner;
public class PrimeNumber3 {
public static boolean isPrime(int num){
for (int i = 2; i < num; i++) {//运行效率不高
if ((num % i) == 0) {
return false;
}
}
return true;
}
public static void main(String[] args){

int begin;
int end;
Scanner in = new Scanner(System.in);
System.out.println("请输入起始数值：");
begin = in.nextInt();
System.out.println("请输入末尾数值：");
end = in.nextInt();
for(int i = begin;i<=end;i++){
if(isPrime(i)){
System.out.print(i + " ");
}
}
}
}