线程池创建ThreadPoolExecutor

最新推荐文章于 2024-07-29 16:34:58 发布

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#threadPool #线程池

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本文介绍如何使用Java创建线程池，并详细解析了ThreadPoolExecutor构造方法的参数及其意义，包括核心线程数、最大线程数、线程空闲时间等。同时展示了自定义线程工厂和拒绝策略的方法。

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先贴出一个创建线程池的实例：

import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

public class ThreadPoolDemo {
	private ThreadPoolExecutor threadPool = null ;
	
	public ThreadPoolDemo(){
		threadPool = new ThreadPoolExecutor(5, 
				10, 
				30, 
				TimeUnit.SECONDS,
				new LinkedBlockingQueue<Runnable>() ,
				new ThreadNameFactory("myThread", false) , 
				new MyAbortPolicy("ThreadName")) ;
	}
}

import java.util.concurrent.ThreadFactory;
import java.util.concurrent.atomic.AtomicInteger;

public class ThreadNameFactory implements ThreadFactory{
	private static AtomicInteger curThre = new AtomicInteger(1) ;
	
	private  AtomicInteger threadNum = new AtomicInteger(1);
	
	private String namePre ; 
	
	private boolean isW  ;
	
	private final ThreadGroup mGroup;
	
	public ThreadNameFactory(String namePre , boolean isW){
		this.namePre = namePre +"-"+curThre.getAndIncrement() ;
		this.isW = isW ; 
		SecurityManager sys = System.getSecurityManager() ;
		mGroup = ( sys == null ) ? Thread.currentThread().getThreadGroup() : sys.getThreadGroup();
 	}
	@Override
	public Thread newThread(Runnable arg0) {
		Thread thread = new Thread(mGroup , this.namePre+"-"+threadNum.getAndIncrement() );
		thread.setDaemon(isW);
		return thread;
	}
}

import java.util.concurrent.RejectedExecutionException;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.ThreadPoolExecutor.AbortPolicy;

public class MyAbortPolicy extends AbortPolicy{
	private String runName ; 
	
	public MyAbortPolicy(String runName){
		this.runName = runName ;
	}
	@Override
    public void rejectedExecution(Runnable r, ThreadPoolExecutor e) {
    	String msg = String.format("Thread pool is EXHAUSTED!" +
                " Thread Name: %s, Pool Size: %d (active: %d, core: %d, max: %d, largest: %d), Task: %d (completed: %d)," +
                " Executor status:(isShutdown:%s, isTerminated:%s, isTerminating:%s)" ,
                runName, e.getPoolSize(), e.getActiveCount(), e.getCorePoolSize(), e.getMaximumPoolSize(), e.getLargestPoolSize(),
                e.getTaskCount(), e.getCompletedTaskCount(), e.isShutdown(), e.isTerminated(), e.isTerminating());
        throw new RejectedExecutionException(msg);
        
    }
}

构造方法：

public ThreadPoolExecutor(int corePoolSize,  
                          int maximumPoolSize,  
                          long keepAliveTime,  
                          TimeUnit unit,  
                          BlockingQueue<Runnable> workQueue,  
                          ThreadFactory threadFactory ,

                          RejectedExecutionHandler handler) {  
    this(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue,  
         Executors.defaultThreadFactory(), handler);  
}

参数解释：

corePoolSize：核心线程数，会一直存活，即使没有任务，线程池也会维护线程的最少数量
maximumPoolSize：线程池维护线程的最大数量
keepAliveTime：线程池维护线程所允许的空闲时间，当线程空闲时间达到keepAliveTime，该线程会退出，直到线程数量等于corePoolSize。如果allowCoreThreadTimeout设置为true，则所有线程均会退出直到线程数量为0。
unit：线程池维护线程所允许的空闲时间的单位、可选参数值为：TimeUnit中的几个静态属性：NANOSECONDS、MICROSECONDS、MILLISECONDS、SECONDS。
workQueue：线程池所使用的缓冲队列，常用的是：java.util.concurrent.ArrayBlockingQueue、LinkedBlockingQueue、SynchronousQueue
handler：线程池中的数量大于maximumPoolSize，对拒绝任务的处理策略，默认值ThreadPoolExecutor.AbortPolicy()。

threadFactory :线程生成工厂