Java并发编程中使用Executors类创建和管理线程的用法

2024-03-21 11:15:03 256

1.类Executors
Executors类可以看做一个“工具类”。援引JDK1.6API中的介绍：
此包中所定义的Executor、ExecutorService、ScheduledExecutorService、ThreadFactory和Callable类的工厂和实用方法。此类支持以下各种方法：
（1）创建并返回设置有常用配置字符串的ExecutorService的方法。
（2）创建并返回设置有常用配置字符串的ScheduledExecutorService的方法。
（3）创建并返回“包装的”ExecutorService方法，它通过使特定于实现的方法不可访问来禁用重新配置。
（4）创建并返回ThreadFactory的方法，它可将新创建的线程设置为已知的状态。
（5）创建并返回非闭包形式的Callable的方法，这样可将其用于需要Callable的执行方法中。
通过这个类能够获得多种线程池的实例，例如可以调用newSingleThreadExecutor()获得单线程的ExecutorService，调用newFixedThreadPool()获得固定大小线程池的ExecutorService，等等。拿到ExecutorService可以做的事情就比较多了，最简单的是用它来执行Runnable对象，也可以执行一些实现了Callable<T>的对象。用Thread的start()方法没有返回值，如果该线程执行的方法有返回值那用ExecutorService就再好不过了，可以选择submit()、invokeAll()或者invokeAny()，根据具体情况选择合适的方法即可。
此类中提供的一些方法有：
1.1publicstaticExecutorServicenewCachedThreadPool()
创建一个可根据需要创建新线程的线程池，但是在以前构造的线程可用时将重用它们。对于执行很多短期异步任务的程序而言，这些线程池通常可提高程序性能。

1.2publicstaticExecutorServicenewFixedThreadPool(intnThreads)
创建一个可重用固定线程数的线程池，以共享的无界队列方式来运行这些线程。

1.3publicstaticExecutorServicenewSingleThreadExecutor()
创建一个使用单个worker线程的Executor，以无界队列方式来运行该线程。

这三个方法都可以配合接口ThreadFactory的实例一起使用。并且返回一个ExecutorService接口的实例。
2.接口ThreadFactory
根据需要创建新线程的对象。使用线程工厂就无需再手工编写对newThread的调用了，从而允许应用程序使用特殊的线程子类、属性等等。
此接口最简单的实现就是：

classSimpleThreadFactoryimplementsThreadFactory{
publicThreadnewThread(Runnabler){
returnnewThread(r);
}
}

3.接口ExecutorService
该接口提供了管理终止的方法。
4.创建标准线程池启动线程
4.1提供一个简单的实现Runnable接口的线程
MyThread.java

packagecom.zj.concurrency.executors;

publicclassMyThreadimplementsRunnable{
privateintcount=1,number;

publicMyThread(intnum){
number=num;
System.out.println("CreateThread-"+number);
}

publicvoidrun(){
while(true){
System.out.println("Thread-"+number+"run"+count+"time(s)");
if(++count==3)
return;
}
}
}

这个线程会打印出相应的创建和执行信息。

4.2使用CachedThreadPool启动线程
CachedThreadPool.java

packagecom.zj.concurrency.executors;
importjava.util.concurrent.ExecutorService;
importjava.util.concurrent.Executors;

publicclassCachedThreadPool{
publicstaticvoidmain(String[]args){
ExecutorServiceexec=Executors.newCachedThreadPool();
for(inti=0;i<5;i++)
exec.execute(newMyThread(i));
exec.shutdown();
}
}

结果：

CreateThread-0
CreateThread-1
CreateThread-2
CreateThread-3
Thread-0run1time(s)
Thread-0run2time(s)
Thread-1run1time(s)
Thread-1run2time(s)
Thread-2run1time(s)
Thread-2run2time(s)
CreateThread-4
Thread-4run1time(s)
Thread-4run2time(s)
Thread-3run1time(s)
Thread-3run2time(s)

4.3使用FixedThreadPool启动线程

FixedThreadPool.java
packagecom.zj.concurrency.executors;
importjava.util.concurrent.ExecutorService;
importjava.util.concurrent.Executors;

publicclassFixedThreadPool{
publicstaticvoidmain(String[]args){
ExecutorServiceexec=Executors.newFixedThreadPool(2);
for(inti=0;i<5;i++)
exec.execute(newMyThread(i));
exec.shutdown();
}
}

结果：

CreateThread-0
CreateThread-1
CreateThread-2
CreateThread-3
CreateThread-4
Thread-0run1time(s)
Thread-0run2time(s)
Thread-2run1time(s)
Thread-2run2time(s)
Thread-3run1time(s)
Thread-3run2time(s)
Thread-4run1time(s)
Thread-4run2time(s)
Thread-1run1time(s)
Thread-1run2time(s)

4.4使用SingleThreadExecutor启动线程
SingleThreadExecutor.java

packagecom.zj.concurrency.executors;
importjava.util.concurrent.ExecutorService;
importjava.util.concurrent.Executors;

publicclassSingleThreadExecutor{
publicstaticvoidmain(String[]args){
ExecutorServiceexec=Executors.newSingleThreadExecutor();
for(inti=0;i<5;i++)
exec.execute(newMyThread(i));
exec.shutdown();
}
}

结果：

CreateThread-0
CreateThread-1
CreateThread-2
CreateThread-3
CreateThread-4
Thread-0run1time(s)
Thread-0run2time(s)
Thread-1run1time(s)
Thread-1run2time(s)
Thread-2run1time(s)
Thread-2run2time(s)
Thread-3run1time(s)
Thread-3run2time(s)
Thread-4run1time(s)
Thread-4run2time(s)

5.配合ThreadFactory接口的使用
我们试图给线程加入daemon和priority的属性设置。
5.1设置后台线程属性
DaemonThreadFactory.java

packagecom.zj.concurrency.executors.factory;
importjava.util.concurrent.ThreadFactory;

publicclassDaemonThreadFactoryimplementsThreadFactory{
publicThreadnewThread(Runnabler){
Threadt=newThread(r);
t.setDaemon(true);
returnt;
}
}

5.2设置优先级属性
最高优先级MaxPriorityThreadFactory.java

packagecom.zj.concurrency.executors.factory;
importjava.util.concurrent.ThreadFactory;

publicclassMaxPriorityThreadFactoryimplementsThreadFactory{
publicThreadnewThread(Runnabler){
Threadt=newThread(r);
t.setPriority(Thread.MAX_PRIORITY);
returnt;
}
}

最低优先级MinPriorityThreadFactory.java

packagecom.zj.concurrency.executors.factory;
importjava.util.concurrent.ThreadFactory;

publicclassMinPriorityThreadFactoryimplementsThreadFactory{
publicThreadnewThread(Runnabler){
Threadt=newThread(r);
t.setPriority(Thread.MIN_PRIORITY);
returnt;
}
}

5.3启动带有属性设置的线程
ExecFromFactory.java

packagecom.zj.concurrency.executors;
importjava.util.concurrent.ExecutorService;
importjava.util.concurrent.Executors;
importcom.zj.concurrency.executors.factory.DaemonThreadFactory;
importcom.zj.concurrency.executors.factory.MaxPriorityThreadFactory;
importcom.zj.concurrency.executors.factory.MinPriorityThreadFactory;

publicclassExecFromFactory{
publicstaticvoidmain(String[]args)throwsException{
ExecutorServicedefaultExec=Executors.newCachedThreadPool();
ExecutorServicedaemonExec=Executors
.newCachedThreadPool(newDaemonThreadFactory());
ExecutorServicemaxPriorityExec=Executors
.newCachedThreadPool(newMaxPriorityThreadFactory());
ExecutorServiceminPriorityExec=Executors
.newCachedThreadPool(newMinPriorityThreadFactory());
for(inti=0;i<10;i++)
daemonExec.execute(newMyThread(i));
for(inti=10;i<20;i++)
if(i==10)
maxPriorityExec.execute(newMyThread(i));
elseif(i==11)
minPriorityExec.execute(newMyThread(i));
else
defaultExec.execute(newMyThread(i));
}
}

结果：

CreateThread-0
CreateThread-1
CreateThread-2
CreateThread-3
Thread-0run1time(s)
Thread-0run2time(s)
Thread-1run1time(s)
Thread-1run2time(s)
Thread-2run1time(s)
Thread-2run2time(s)
CreateThread-4
Thread-4run1time(s)
Thread-4run2time(s)
CreateThread-5
Thread-5run1time(s)
Thread-5run2time(s)
CreateThread-6
CreateThread-7
Thread-7run1time(s)
Thread-7run2time(s)
CreateThread-8
Thread-8run1time(s)
Thread-8run2time(s)
CreateThread-9
CreateThread-10
Thread-10run1time(s)
Thread-10run2time(s)
CreateThread-11
Thread-9run1time(s)
Thread-9run2time(s)
Thread-6run1time(s)
Thread-6run2time(s)
Thread-3run1time(s)
Thread-3run2time(s)
CreateThread-12
CreateThread-13
CreateThread-14
Thread-12run1time(s)
Thread-12run2time(s)
Thread-13run1time(s)
Thread-13run2time(s)
CreateThread-15
Thread-15run1time(s)
Thread-15run2time(s)
CreateThread-16
Thread-16run1time(s)
Thread-16run2time(s)
CreateThread-17
CreateThread-18
CreateThread-19
Thread-14run1time(s)
Thread-14run2time(s)
Thread-17run1time(s)
Thread-17run2time(s)
Thread-18run1time(s)
Thread-18run2time(s)
Thread-19run1time(s)
Thread-19run2time(s)
Thread-11run1time(s)
Thread-11run2time(s)

Java并发编程中使用Executors类创建和管理线程的用法

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