用JAVA编程，从键盘输入一数，输出一个小于等于这个数的所有质数

用JAVA编程，从键盘输入一数，输出一个小于等于这个数的所有质数

import java.util.Scanner;

public class Ab {

public static void main(String[] args) {
System.out.print("Please input a digit: ");

int num = new Scanner(System.in).nextInt();

for(int i = 2; i <= num; i++){
boolean isPrime = true;
for(int j = 2; j <= Math.sqrt(i); j++){
if(i % j == 0){
isPrime = false;
break;
}
}

if(isPrime){
System.out.println(i);
}
}

}

}

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
public class Test {
public static void main(String[] args) throws NumberFormatException, IOException{
System.out.println("请输入一个整数");
BufferedReader strin=new BufferedReader(new InputStreamReader(System.in));
int num=Integer.parseInt(strin.readLine());
if(num>0){
for(int i=2;i<=num;i++){
boolean flag = true;
for(int j = 2; j <=Math.sqrt(i); j++){
if(i % j == 0){
flag = false;
break;
}
}
if(flag){
System.out.println(i);
}
}
}else{
System.out.println("请重新输入！");
}
}
}