Java t时间解优化

如何优化此代码，使时间不超过2000ms 变量输入（1）是要作为tprome检查的数字计数

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另一条下一行扫描从（>1&&可能是codegolf的东西？？更适合可能是codegolf的东西？？更适合

import java.util.Scanner;
import java.util.ArrayList;
import java.io.BufferedReader;
import java.io.InputStreamReader;

public class TprimePractise {

public static void main(String[] args) throws Exception {
    BufferedReader br = 
    new BufferedReader(new InputStreamReader(System.in));
    String line = br.readLine();
    int input = Integer.valueOf(line);
    line = br.readLine();
    long sqrt, x;
    for (String num : line.split("\\s")) {
        x = Long.valueOf(num);

        if (x == 1) {
            System.out.println("NO");
            continue;
        }
        sqrt = (long) Math.sqrt(x);
        if (sqrt * sqrt == x && isPrime(sqrt)) {
            System.out.println("YES");
        } else {
            System.out.println("NO");
        }

      }
   }

   public static boolean isPrime(long num) {

    for (int j = (int) num / 2; j >= 2; j--) {
        if (num % j == 0) {
            return false;
        }
    }
    return true;
   }