1. 类 executors
executors类可以看做一个“工具类”。援引jdk1.6 api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：
1.1 public static executorservice newcachedthreadpool()
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。
1.2 public static executorservice newfixedthreadpool(int nthreads)
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。
1.3 public static executorservice newsinglethreadexecutor()
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 new thread 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：
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class simplethreadfactory implements threadfactory {
public thread newthread(runnable r) {
return new thread(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
package com.zj.concurrency.executors;
public class mythread implements runnable {
private int count = 1, number;
public mythread(int num) {
number = num;
system.out.println("create thread-" + number);
}
public void run() {
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
package com.zj.concurrency.executors;
import java.util.concurrent.executorservice;
import java.util.concurrent.executors;
public class cachedthreadpool {
public static void main(string[] args) {
executorservice exec = executors.newcachedthreadpool();
for (int i = 0; i < 5; i++)
exec.execute(new mythread(i));
exec.shutdown();
}
}
结果：
create thread-0 create thread-1 create thread-2 create thread-3 thread-0 run 1 time(s) thread-0 run 2 time(s) thread-1 run 1 time(s) thread-1 run 2 time(s) thread-2 run 1 time(s) thread-2 run 2 time(s) create thread-4 thread-4 run 1 time(s) thread-4 run 2 time(s) thread-3 run 1 time(s) thread-3 run 2 time(s)
4.3 使用fixedthreadpool启动线程
fixedthreadpool.java
package com.zj.concurrency.executors;
import java.util.concurrent.executorservice;
import java.util.concurrent.executors;
public class fixedthreadpool {
public static void main(string[] args) {
executorservice exec = executors.newfixedthreadpool(2);
for (int i = 0; i < 5; i++)
exec.execute(new mythread(i));
exec.shutdown();
}
}
结果：
create thread-0 create thread-1 create thread-2 create thread-3 create thread-4 thread-0 run 1 time(s) thread-0 run 2 time(s) thread-2 run 1 time(s) thread-2 run 2 time(s) thread-3 run 1 time(s) thread-3 run 2 time(s) thread-4 run 1 time(s) thread-4 run 2 time(s) thread-1 run 1 time(s) thread-1 run 2 time(s)
4.4 使用singlethreadexecutor启动线程
singlethreadexecutor.java
package com.zj.concurrency.executors;
import java.util.concurrent.executorservice;
import java.util.concurrent.executors;
public class singlethreadexecutor {
public static void main(string[] args) {
executorservice exec = executors.newsinglethreadexecutor();
for (int i = 0; i < 5; i++)
exec.execute(new mythread(i));
exec.shutdown();
}
}
结果：
create thread-0 create thread-1 create thread-2 create thread-3 create thread-4 thread-0 run 1 time(s) thread-0 run 2 time(s) thread-1 run 1 time(s) thread-1 run 2 time(s) thread-2 run 1 time(s) thread-2 run 2 time(s) thread-3 run 1 time(s) thread-3 run 2 time(s) thread-4 run 1 time(s) thread-4 run 2 time(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
package com.zj.concurrency.executors.factory;
import java.util.concurrent.threadfactory;
public class daemonthreadfactory implements threadfactory {
public thread newthread(runnable r) {
thread t = new thread(r);
t.setdaemon(true);
return t;
}
}
5.2 设置优先级属性
最高优先级maxprioritythreadfactory.java
package com.zj.concurrency.executors.factory;
import java.util.concurrent.threadfactory;
public class maxprioritythreadfactory implements threadfactory {
public thread newthread(runnable r) {
thread t = new thread(r);
t.setpriority(thread.max_priority);
return t;
}
}
最低优先级minprioritythreadfactory.java
package com.zj.concurrency.executors.factory;
import java.util.concurrent.threadfactory;
public class minprioritythreadfactory implements threadfactory {
public thread newthread(runnable r) {
thread t = new thread(r);
t.setpriority(thread.min_priority);
return t;
}
}
5.3启动带有属性设置的线程
execfromfactory.java
package com.zj.concurrency.executors;
import java.util.concurrent.executorservice;
import java.util.concurrent.executors;
import com.zj.concurrency.executors.factory.daemonthreadfactory;
import com.zj.concurrency.executors.factory.maxprioritythreadfactory;
import com.zj.concurrency.executors.factory.minprioritythreadfactory;
public class execfromfactory {
public static void main(string[] args) throws exception {
executorservice defaultexec = executors.newcachedthreadpool();
executorservice daemonexec = executors
.newcachedthreadpool(new daemonthreadfactory());
executorservice maxpriorityexec = executors
.newcachedthreadpool(new maxprioritythreadfactory());
executorservice minpriorityexec = executors
.newcachedthreadpool(new minprioritythreadfactory());
for (int i = 0; i < 10; i++)
daemonexec.execute(new mythread(i));
for (int i = 10; i < 20; i++)
if (i == 10)
maxpriorityexec.execute(new mythread(i));
else if (i == 11)
minpriorityexec.execute(new mythread(i));
else
defaultexec.execute(new mythread(i));
}
}
结果：
create thread-0 create thread-1 create thread-2 create thread-3 thread-0 run 1 time(s) thread-0 run 2 time(s) thread-1 run 1 time(s) thread-1 run 2 time(s) thread-2 run 1 time(s) thread-2 run 2 time(s) create thread-4 thread-4 run 1 time(s) thread-4 run 2 time(s) create thread-5 thread-5 run 1 time(s) thread-5 run 2 time(s) create thread-6 create thread-7 thread-7 run 1 time(s) thread-7 run 2 time(s) create thread-8 thread-8 run 1 time(s) thread-8 run 2 time(s) create thread-9 create thread-10 thread-10 run 1 time(s) thread-10 run 2 time(s) create thread-11 thread-9 run 1 time(s) thread-9 run 2 time(s) thread-6 run 1 time(s) thread-6 run 2 time(s) thread-3 run 1 time(s) thread-3 run 2 time(s) create thread-12 create thread-13 create thread-14 thread-12 run 1 time(s) thread-12 run 2 time(s) thread-13 run 1 time(s) thread-13 run 2 time(s) create thread-15 thread-15 run 1 time(s) thread-15 run 2 time(s) create thread-16 thread-16 run 1 time(s) thread-16 run 2 time(s) create thread-17 create thread-18 create thread-19 thread-14 run 1 time(s) thread-14 run 2 time(s) thread-17 run 1 time(s) thread-17 run 2 time(s) thread-18 run 1 time(s) thread-18 run 2 time(s) thread-19 run 1 time(s) thread-19 run 2 time(s) thread-11 run 1 time(s) thread-11 run 2 time(s)
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