java - 多线程 java xsync

Question

我是多线程新手。我需要使用多个线程通过部分和来计算积分。我想知道是否所有线程都完成了计算以显示总和，我正在使用 sleep(500) 来完成它，但这很愚蠢。我怎样才能以正确的方式做到这一点？

public class MainClass {
    private static int threadCount=10;
    public static double generalSum=0;
    private static ArrayList<CalculatingThread> threads;
    public static  void main(String[] args){
        Calculator.setA(0);
        Calculator.setB(2);
        Calculator.setN(500);
        threads=new ArrayList<CalculatingThread>();
        int div=500/threadCount;
        for (int i=0; i<div;i++){
            CalculatingThread thread=new CalculatingThread();
            thread.setJK(i*10,(i+1)*10-1);
            thread.start();
            threads.add(thread);
        }
        try {
            Thread.currentThread().sleep(500);
            System.out.println(generalSum);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

public class CalculatingThread extends Thread {
    private int j;
    private int k;

    @Override
    public void run(){
        System.out.println("Partial sum: " + Calculator.calcIntegral(j, k));
        Calculator.addToSumm(Calculator.calcIntegral(j, k));
        //this.notify();
    }

    public void setJK(int j,int k) {
        this.j = j;
        this.k=k;
    }
}


public class Calculator {
    private  static double a;
    private  static double b;
    private  static int n;

    private static double InFunction(double x){
        return Math.sin(x);
    }
    private double sum=0;

    public static void setA(double a) {
        Calculator.a = a;
    }

    public static void setB(double b) {
        Calculator.b = b;
    }

    public static void setN(int n) {
        Calculator.n = n;
    }

    public static double calcIntegral(int j,int k)
    {
        double result, h;
        int i;

        h = (b-a)/n; //Шаг сетки
        result = 0;

        for(i=j; i <= k; i++)
        {
            result += InFunction(a + h * i - h/2); //Вычисляем в средней точке и добавляем в сумму
        }
        result *= h;
        return result;
    }

    public static synchronized void addToSumm(double sum){
        MainClass.generalSum+=sum;
    }
}

附注抱歉，我知道代码很愚蠢，我稍后会重构它

Answer 1

替换

Thread.currentThread().sleep(500);

与

for (Thread thread : threads) {
    thread.join();
 }

这将使主线程等待，直到所有创建的线程完成。也可以引用wait until all threads finish their work in java