多线程计算stream parallelStream

import java.util.ArrayList;
import java.util.List;
import java.util.Random;

/**
 * 多线程计算
 */
public class ParallelStreamAPI {

    public static void main(String[] args) {

        List<Integer> nums = new ArrayList<>();
        Random random = new Random();
        for(int i=0; i<10000; i++) nums.add(1000000 + random.nextInt(1000000));

        long startTime = System.currentTimeMillis();
        nums.forEach(n -> {isPrime(n);});
        long endTime = System.currentTimeMillis();
        System.out.println("耗时：" + (endTime - startTime));


        //使用stream parallelStream
        startTime = System.currentTimeMillis();
        nums.parallelStream().forEach(n -> {isPrime(n);});
        endTime = System.currentTimeMillis();
        System.out.println("耗时：" + (endTime - startTime));
    }

    /**
     * 判断一个数是不是质素/素数
     * @param num
     * @return
     */
    static boolean isPrime(int num) {
        for(int i=2; i<=num/2; i++) {
            if(num % i == 0) return false;
        }
        return true;
    }

}