多线程用于计算1到1000000000之间的数字累加，并比较多个线程耗时多少

Posted 2020-08-08 懒猫要学习512

package cn.java.core.ch03.job.job03;

import java.util.Scanner;

public class MultiCalc {
private long startTime = 0L;
private long endTime =0L;

private long totalResult = 0L;

private Boolean[] isCompleted = null;

public static void main(String[] args) {

(new MultiCalc()).startUp();
}

private boolean isSuccessed(){
for(int i=0;i<isCompleted.length;i++){
if (!isCompleted[i])
return false;
}
return true;
}


private void startUp(){
int threadNum;
long numbers = 100L;

System.out.println("请输入要开启的线程数");
Scanner input = new Scanner(System.in);
threadNum = input.nextInt();
isCompleted = new Boolean[threadNum];

System.out.println("开始计时....");
startTime = System.currentTimeMillis();
for(int i=1;i<=threadNum;i++){
isCompleted[i-1] =false;
Thread t = new Thread(new CalcThread(i,numbers,threadNum));
t.start();
}
synchronized (MultiCalc.this) {
try {

MultiCalc.this.wait();

} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

endTime = System.currentTimeMillis();

System.out.println("计算结果为："+totalResult);
System.out.println("计时结束，总耗时为："+(endTime-startTime)+"ms");
}

class CalcThread implements Runnable{
private long start;
private long end;
private long result;
private int threadIndex;
public CalcThread(int threadIndex,long numbers,int threadNum){
long step = numbers/threadNum;
this.threadIndex = threadIndex;
start = (threadIndex-1)*step+1;
if (threadIndex==threadNum){ //是否是最后一个线程
end = numbers;
}else{
end = threadIndex*step;
}

//System.out.println(Thread.currentThread().getName()+
//"---->"+start+"~"+end);
}
@Override
public void run() {
for(long i=start;i<=end;i++){
try {
Thread.sleep(10);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
result+=i;
}

//System.out.println(result);
synchronized (MultiCalc.this) {
totalResult +=result;
isCompleted[this.threadIndex-1] = true;
if (isSuccessed()){
MultiCalc.this.notify();
}
}
//System.out.println(totalResult);
}
}
}