目前系统中有一个需求需要用到线程,
点击一个按钮,启动一个线程,处理相关业务(这个线程大概10个小时后结束),
当这个线程还没结束时,又点击这个按钮,又会启动一个线程,这样就重复了。当再次点击这个按钮时,如何判断前面那个线程是否已结束?
点击一个按钮,启动一个线程,处理相关业务(这个线程大概10个小时后结束),
当这个线程还没结束时,又点击这个按钮,又会启动一个线程,这样就重复了。当再次点击这个按钮时,如何判断前面那个线程是否已结束?
调试欢乐多
判断当前java进程线程数
thread中是有很多方法来检测是执行过,问题是如何得到之前运行的线程? 然后.isAlive()判断synchronized 只是让数据同步,两个线程还是会同时存在。我要的效果是,当第一个线程在运行时,第二个线程就不让启动
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Future;
import java.util.concurrent.SynchronousQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;public class Test{
private static final BlockingQueue queue=new SynchronousQueue();
// private static final BlockingQueue queue=new LinkedBlockingQueue(1);
private static final ExecutorService threadpool=new ThreadPoolExecutor(1,1,0L,TimeUnit.MILLISECONDS,queue); public static Future submit(final Object obj){
return threadpool.submit(new Callable(){
@Override
public Object call() throws Exception{
// TODO do your job here!
System.out.println(obj);
Thread.sleep(2000);
return obj;
}
});
} public static void main(String...args) throws Exception{
submit("You got it!");
submit("You got it!");
submit("You got it!");
}
}我给的代码默认只有一个任务在工作,之前的未完成自动会抛出异常,自己根据需要进行处理;注释掉的那行意思是允许有一个在等待,总体来说就是倒腾那个queue
SynchronousQueue:0等待,必须先有取等待才允许提交任务;
LinkedBlockingQueue:可以根据需要配置等待任务数。
不行啊 整个WEB应用 一到晚上会有好几个线程在跑批。至于有几个我不确定
我就不解释了,自己看代码:import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Future;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;public class Test{
private static final BlockingQueue queue=new LinkedBlockingQueue();
private static final ExecutorService threadpool=new ThreadPoolExecutor(10,20,0L,TimeUnit.MILLISECONDS,queue); public static Future submit(final String name,final Object obj){
return threadpool.submit(new Callable(){
@Override
public Object call() throws Exception{
// TODO do your job here!
boolean lock=Token.tryLock(name);
if(!lock) return null;
try{
System.out.println(obj);
Thread.sleep(2000);
return obj;
}finally{
Token.unlock(name);
}
}
});
} public static void main(String...args) throws Exception{
submit("t1","You got t1!");
submit("t1","You got t1!");
submit("t1","You got t1!");
submit("t2","You got t2!");
submit("t2","You got t2!");
submit("t2","You got t2!");
Thread.sleep(3000);
submit("t1","You got t1!");
submit("t1","You got t1!");
submit("t1","You got t1!");
submit("t2","You got t2!");
submit("t2","You got t2!");
submit("t2","You got t2!");
} public static class Token{
private static final Lock lockme=new ReentrantLock();
private static final Map<String,Lock> locks=new HashMap<String,Lock>(); public static boolean tryLock(String name){
Lock lock=getLock(name);
return lock.tryLock();
} public static void unlock(String name){
Lock lock=getLock(name);
lock.unlock();
} private static Lock getLock(String name){
lockme.lock();
try{
Lock lock=locks.get(name);
if(lock==null){
lock=new ReentrantLock();
locks.put(name,lock);
}
return lock;
}finally{
lockme.unlock();
}
}
}
}
第一种:你将这个按钮设置为不可用。
第二种:利用socket,说明该端口被暂用,这种一般是整个客户端才会使用。
Pserver = new ServerSocket(1001);
Socket sock = new Socket("127.0.0.1", 1001);
第三种:将线程设定为静态对象,判断是否为空!
我11楼的代码是更通用的实现,能够同时控制多个任务,每个任务限制只能一个实例在执行,执行期间的重复请求被丢弃,任务按名字区分。建议的做法是一个任务一个Action类,任务名就自动用该类的className。
楼主该结贴了!