我的每个线程都睡了2000毫秒,我有10个这样的线程,所以我预计总睡眠时间至少为20秒,但它只会在16-18秒之间出现。对不起,如果我问的是已经被问过的话。这是我到目前为止所拥有的:
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
public class MyThreadPoolApp {
public static void main(String[] args) {
long execTime = System.currentTimeMillis();
CountDownLatch latch = new CountDownLatch(1);
ExecutorService executor = Executors.newFixedThreadPool(10);
for (int i = 0; i < 10; i++) {
executor.submit(new Task());
}
System.out.println("threads submitted and waiting execution");
executor.shutdown();
try {
executor.awaitTermination(1, TimeUnit.MINUTES);
} catch (InterruptedException e) {
}
execTime = System.currentTimeMillis() - execTime;
System.out.format("%d threads finished execution \n",Task.getCount());
System.out.println("thread time : " + Task.getTime());
System.out.println("main time : " + execTime);
}
}
任务在哪里:
public class Task implements Runnable {
private static long totalTime;
private static int count;
public static long getTime(){ return totalTime; }
public static int getCount(){ return count; }
public void run() {
count++;
long startTime = System.currentTimeMillis();
try {
Thread.sleep(2000);
totalTime += System.currentTimeMillis() - startTime;
} catch (InterruptedException e) {}
}
}
我的输出:
threads submitted and waiting execution
10 threads finished execution
thread time : 18001
main time : 2020
答案 0 :(得分:1)
因为你正在搞乱各种线程对totalTime的并发更新。
试试这个:
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
public class MyThreadPoolApp {
public static void main(String[] args) {
long execTime = System.currentTimeMillis();
CountDownLatch latch = new CountDownLatch(1);
ExecutorService executor = Executors.newFixedThreadPool(10);
for (int i = 0; i < 10; i++) {
executor.submit(new Task());
}
System.out.println("threads submitted and waiting execution");
executor.shutdown();
try {
executor.awaitTermination(1, TimeUnit.MINUTES);
} catch (InterruptedException e) {
}
execTime = System.currentTimeMillis() - execTime;
System.out.format("%d threads finished execution \n",Task.getCount());
System.out.println("thread time : " + Task.getTime());
System.out.println("main time : " + execTime);
}
}
class Task implements Runnable {
private static long totalTime;
private static int count;
public static long getTime(){
synchronized(Task.class){
return totalTime;
}
}
private static void addTime(long time){
synchronized(Task.class){
totalTime = totalTime + time;
}
}
public static int getCount(){ return count; }
public void run() {
count++;
long startTime = System.currentTimeMillis();
try {
Thread.sleep(2000);
addTime(System.currentTimeMillis() - startTime);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
修改强> 如您所愿,在run()方法内同步:
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
public class MyThreadPoolApp {
public static void main(String[] args) {
long execTime = System.currentTimeMillis();
CountDownLatch latch = new CountDownLatch(1);
ExecutorService executor = Executors.newFixedThreadPool(10);
for (int i = 0; i < 10; i++) {
executor.submit(new Task());
}
System.out.println("threads submitted and waiting execution");
executor.shutdown();
try {
executor.awaitTermination(1, TimeUnit.MINUTES);
} catch (InterruptedException e) {
}
execTime = System.currentTimeMillis() - execTime;
System.out.format("%d threads finished execution \n",Task.getCount());
System.out.println("thread time : " + Task.getTime());
System.out.println("main time : " + execTime);
}
}
class Task implements Runnable {
private static long totalTime;
private static int count;
public static long getTime(){
synchronized(Task.class){
return totalTime;
}
}
public static int getCount(){ return count; }
public void run() {
count++;
long startTime = System.currentTimeMillis();
try {
Thread.sleep(2000);
synchronized(Task.class){
totalTime += System.currentTimeMillis() - startTime;
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}