Java 建立線程池的四種方式

Java 建立執行緒池的四種方式

#1、newCachedThreadPool 建立一個可快取執行緒池，如果執行緒池長度超過處理需要，可靈活回收空閒線程，若無可回收，則新線程。

2、newFixedThreadPool 建立一個定長執行緒池，可控制執行緒最大並發數，超出的執行緒會在佇列中等待。

3、newScheduledThreadPool 建立一個定長執行緒池，支援定時及週期性任務執行。

4、newSingleThreadExecutor 建立一個單執行緒化的執行緒池，它只會用唯一的工作執行緒來執行任務，保證所有任務都按照指定順序(FIFO, LIFO, 優先權)執行。

newCachedThreadPool

建立一個可快取執行緒池，如果執行緒池長度超過處理需要，可靈活回收空閒線程，

若無可回收，則新建執行緒。

package cn.qbz.thread;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class Test111907 {
    public static void main(String[] args) {
        ExecutorService executorService = Executors.newCachedThreadPool();
        for (int i = 0; i < 10; i++) {
            final int temp = i;
            executorService.execute(new Runnable() {
                @Override
                public void run() {
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    System.out.println(Thread.currentThread().getName() + "   i=" + temp);
                }
            });
        }
    }
}
    public static ExecutorService newCachedThreadPool() {
        return new ThreadPoolExecutor(0, Integer.MAX_VALUE,
                                      60L, TimeUnit.SECONDS,
                                      new SynchronousQueue<Runnable>());
    }

newFixedThreadPool

建立一個定長執行緒池，可控制執行緒最大並發數，超出的執行緒會在佇列中等待。

package cn.qbz.thread;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class Test111907 {
    public static void main(String[] args) {
        ExecutorService executorService = Executors.newFixedThreadPool(3);
        for (int i = 0; i < 10; i++) {
            final int temp = i;
            executorService.execute(new Runnable() {
                @Override
                public void run() {
                    try {
                        Thread.sleep(100);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    System.out.println(Thread.currentThread().getName() + "   i=" + temp);
                }
            });
        }
    }
}
    public static ExecutorService newFixedThreadPool(int nThreads) {
        return new ThreadPoolExecutor(nThreads, nThreads,
                                      0L, TimeUnit.MILLISECONDS,
                                      new LinkedBlockingQueue<Runnable>());
    }

newScheduledThreadPool

建立一個定長執行緒池，支援定時及週期性任務執行。

package cn.qbz.thread;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
public class Test111907 {
    public static void main(String[] args) {
        final long begin = System.currentTimeMillis();
        ExecutorService executorService = Executors.newScheduledThreadPool(3);
        for (int i = 0; i < 10; i++) {
            final int temp = i;
            final long time = begin;
            executorService.schedule(new Runnable() {
                @Override
                public void run() {
                    try {
                        Thread.sleep(100);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    System.out.println(Thread.currentThread().getName() + "   i=" + temp + "   time=" + (System.currentTimeMillis() - time));
                }
            }, 5, TimeUnit.SECONDS);
        }
    }
}
    public static ScheduledExecutorService newScheduledThreadPool(int corePoolSize) {
        return new ScheduledThreadPoolExecutor(corePoolSize);
    }
    public ScheduledThreadPoolExecutor(int corePoolSize) {
        super(corePoolSize, Integer.MAX_VALUE, 0, TimeUnit.NANOSECONDS,
              new DelayedWorkQueue());
    }

newSingleThreadExecutor

建立一個單執行緒化的執行緒池，它只會用唯一的工作執行緒來執行任務，

#保證所有任務依照指定順序(FIFO, LIFO, 優先權)執行。

package cn.qbz.thread;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
public class Test111907 {
    public static void main(String[] args) {
        ExecutorService executorService = Executors.newSingleThreadExecutor();
        for (int i = 0; i < 10; i++) {
            final int temp = i;
            executorService.execute(new Runnable() {
                @Override
                public void run() {
                    try {
                        Thread.sleep(100);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    System.out.println(Thread.currentThread().getName() + "   i=" + temp);
                }
            });
        }
    }
}

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