ThreadPoolExecutor是大家在日常開發(fā)中經(jīng)常用到的類，java.util.concurrent包提供了 java.util.concurrent.Executors工具類方便大家創(chuàng)建線程池。
Executors
1、創(chuàng)建固定大小線程池
ExecutorService es = Executors.newFixedThreadPool(20);
Executors.newFixedThreadPool() 源碼如下：
public static ExecutorService newFixedThreadPool(int nThreads) {
return new ThreadPoolExecutor(nThreads, nThreads,
0L, TimeUnit.MILLISECONDS,
new LinkedBlockingQueue<Runnable>());
}
2、創(chuàng)建單線程線程池
ExecutorService es = Executors.newSingleThreadExecutor();
Executors.newSingleThreadExecutor()源碼如下：
public static ExecutorService newSingleThreadExecutor() {
return new FinalizableDelegatedExecutorService
(new ThreadPoolExecutor(1, 1,
0L, TimeUnit.MILLISECONDS,
new LinkedBlockingQueue<Runnable>()));
}
3、創(chuàng)建緩存的線程池
ExecutorService es = Executors.newCachedThreadPool();
Executors.newCachedThreadPool() 源碼如下：
public static ExecutorService newCachedThreadPool() {
return new ThreadPoolExecutor(0, Integer.MAX_VALUE,
60L, TimeUnit.SECONDS,
new SynchronousQueue<Runnable>());
}
** 不建議大家使用 java.util.concurrent.Executors，推薦直接使用 new ThreadPoolExecutor() 來創(chuàng)建，這樣更清楚線程池的參數(shù)配置。**
ThreadPoolExecutor
首先，看看 java.util.concurrent.ThreadPoolExecutor 的構(gòu)造方法，如下：
package java.util.concurrent;
public class ThreadPoolExecutor extends AbstractExecutorService {
/**構(gòu)造方法**/
public ThreadPoolExecutor(int corePoolSize,
int maximumPoolSize,
long keepAliveTime,
TimeUnit unit,
BlockingQueue<Runnable> workQueue) {
this(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue,
Executors.defaultThreadFactory(), defaultHandler);
}
public ThreadPoolExecutor(int corePoolSize,
int maximumPoolSize,
long keepAliveTime,
TimeUnit unit,
BlockingQueue<Runnable> workQueue,
ThreadFactory threadFactory) {
this(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue,
threadFactory, defaultHandler);
}
public ThreadPoolExecutor(int corePoolSize,
int maximumPoolSize,
long keepAliveTime,
TimeUnit unit,
BlockingQueue<Runnable> workQueue,
RejectedExecutionHandler handler) {
this(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue,
Executors.defaultThreadFactory(), handler);
}
public ThreadPoolExecutor(int corePoolSize,
int maximumPoolSize,
long keepAliveTime,
TimeUnit unit,
BlockingQueue<Runnable> workQueue,
ThreadFactory threadFactory,
RejectedExecutionHandler handler) {
if (corePoolSize < 0 ||
maximumPoolSize <= 0 ||
maximumPoolSize < corePoolSize ||
keepAliveTime < 0)
throw new IllegalArgumentException();
if (workQueue == null || threadFactory == null || handler == null)
throw new NullPointerException();
this.corePoolSize = corePoolSize;
this.maximumPoolSize = maximumPoolSize;
this.workQueue = workQueue;
this.keepAliveTime = unit.toNanos(keepAliveTime);
this.threadFactory = threadFactory;
this.handler = handler;
}
}
