Java裏面線程池的頂級接口是Executor，但是嚴格意義上講Executor並不是一個線程池，而是一個執行線程的工具。真正的線程池接口是ExecutorService.
1.newCachedThreadPool
爲每一個任務創建一個線程，並且可以重用已有的線程，無核心線程數量，超過60s的空閒線程將會被啓用
/**無參構造方法*/
public static ExecutorService newCachedThreadPool() {
return new ThreadPoolExecutor(0, Integer.MAX_VALUE,
60L, TimeUnit.SECONDS,
new SynchronousQueue<Runnable>());
}
/**有參的構造方法，可以傳入threadFactory*/
public static ExecutorService newCachedThreadPool(ThreadFactory threadFactory) {
return new ThreadPoolExecutor(0, Integer.MAX_VALUE,
60L, TimeUnit.SECONDS,
new SynchronousQueue<Runnable>(),
threadFactory);
}
2.newFixedTbreadPool
核心線程數和最大線程數是相同的，無空閒線程，核心線程數無限時要求，可以創建固定大小的線程數量，阻塞隊列沒有大小限制
/**創建固定大小的線程數*/
public static ExecutorService newFixedThreadPool(int nThreads) {
return new ThreadPoolExecutor(nThreads, nThreads,
0L, TimeUnit.MILLISECONDS,
new LinkedBlockingQueue<Runnable>());
}
/**創建固定大小的線程數，並可以指定threadFactory*/
public static ExecutorService newFixedThreadPool(int nThreads, ThreadFactory threadFactory) {
return new ThreadPoolExecutor(nThreads, nThreads,
0L, TimeUnit.MILLISECONDS,
new LinkedBlockingQueue<Runnable>(),
threadFactory);
3.newScheduledThreadPool
延期和定時執行線程的線程池，固定的核心線程數，最大線程數沒有限制，空閒的線程會立即啓用
/**創建固定大小的corePool*/
public static ScheduledExecutorService newScheduledThreadPool(int corePoolSize) {
return new ScheduledThreadPoolExecutor(corePoolSize);
}
/**查看ScheduledThreadPoolExecutor類，發現是集成的ThreadPoolExecutor*/
public ScheduledThreadPoolExecutor(int corePoolSize) {
super(corePoolSize, Integer.MAX_VALUE, 0, NANOSECONDS,
new DelayedWorkQueue());
}
/**創建固定大小的corePool,並指定threadFactory*/
public static ScheduledExecutorService newScheduledThreadPool(
int corePoolSize, ThreadFactory threadFactory) {
return new ScheduledThreadPoolExecutor(corePoolSize, threadFactory);
}
/**查看ScheduledThreadPoolExecutor類，發現是集成的ThreadPoolExecutor*/
public ScheduledThreadPoolExecutor(int corePoolSize,
ThreadFactory threadFactory) {
super(corePoolSize, Integer.MAX_VALUE, 0, NANOSECONDS,
new DelayedWorkQueue(), threadFactory);
4.newSingleThreadExecutor
創建只有一個的核心線程，只處理一個線程，不能處理併發
/**無參*/
public static ExecutorService newSingleThreadExecutor() {
return new FinalizableDelegatedExecutorService
(new ThreadPoolExecutor(1, 1,
0L, TimeUnit.MILLISECONDS,
new LinkedBlockingQueue<Runnable>()));
}
/**指定threadFactory*/
public static ScheduledExecutorService newSingleThreadScheduledExecutor(ThreadFactory threadFactory) {
return new DelegatedScheduledExecutorService
(new ScheduledThreadPoolExecutor(1, threadFactory));
}