Java/com/study/demo6/SumThread.java

package com.study.demo6;

public class SumThread {
  static class PartSumTask implements Runnable {
    private final int[] array;
    private final int start;
    private final int end;
    public long result;

    public PartSumTask(int[] array, int start, int end) {
      this.array = array;
      this.start = start;
      this.end = end;
    }

    @Override
    public void run() {
      long sum = 0;
      for (int i = start; i <= end; i++) {
        sum += array[i];
      }
      result = sum;
    }
  }

  public static void main(String[] args) throws InterruptedException {
    int size = 1_000_000;
    int[] array = new int[size];
    for (int i = 0; i < size; i++) {
      array[i] = i;
    }

    PartSumTask task1 = new PartSumTask(array, 0, 333_333);
    PartSumTask task2 = new PartSumTask(array, 333_334, 666_666);
    PartSumTask task3 = new PartSumTask(array, 666_667, 999_999);

    Thread t1 = new Thread(task1);
    Thread t2 = new Thread(task2);
    Thread t3 = new Thread(task3);

    t1.start();
    t2.start();
    t3.start();

    t1.join();
    t2.join();
    t3.join();

    long total = task1.result + task2.result + task3.result;
    System.out.println("总和为：" + total);
  }
}