详见:http://blog.yemou.net/article/query/info/tytfjhfascvhzxcyt125
毫无疑问 Runnable会进行异步执行,此处不多说,主要说明Callable的使用,看实例:
1、
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public class ThreadTest {
public static void main(String[] args) throws InterruptedException, ExecutionException {
ExecutorService executor = Executors.newFixedThreadPool( 4 );
MyTread m1 = new MyTread();
Future f = executor.submit(m1);
// System.out.println(f.get());
executor.shutdown();
System.out.println( "主线程执行完了" );
}
} |
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class MyTread implements Callable<String> {
@Override
public String call() {
try {
System.out.println( "线程调度:" + Thread.currentThread());
TimeUnit.SECONDS.sleep( 3 );
} catch (InterruptedException e) {
e.printStackTrace();
}
return "123" ;
}
} |
此程序虽然获取了call方法的返回值,但是没有做处理,所以主线程main和m1同时执行,执行结果如下:
主线程执行完了
线程调度:Thread[pool-1-thread-1,5,main]
2、
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public class ThreadTest {
public static void main(String[] args) throws InterruptedException, ExecutionException {
ExecutorService executor = Executors.newFixedThreadPool( 4 );
MyTread m1 = new MyTread();
Future f = executor.submit(m1);
System.out.println(f.get()); // 进行了输出
executor.shutdown();
System.out.println( "主线程执行完了" );
}
} |
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class MyTread implements Callable<String> {
@Override
public String call() {
try {
System.out.println( "线程调度:" + Thread.currentThread());
TimeUnit.SECONDS.sleep( 3 );
} catch (InterruptedException e) {
e.printStackTrace();
}
return "123" ;
}
} |
在2中,对m1中call方法的返回值在main中进行了处理(输出),所以在此种情况下,main需要等待m1执行完,再继续执行,执行结果如下
线程调度:Thread[pool-1-thread-1,5,main]
123
主线程执行完了
3、再看当主线程中同时启动两个由Callable生成的线程时
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public class ThreadTest {
public static void main(String[] args) throws InterruptedException, ExecutionException {
ExecutorService executor = Executors.newFixedThreadPool( 4 );
MyTread m1 = new MyTread();
MyTread2 m2 = new MyTread2();
Long time1 = TimeUnit.MILLISECONDS.toSeconds(System.currentTimeMillis());
Future f = executor.submit(m1);
Future f2 = executor.submit(m2);
System.out.println(f.get()); // 进行了输出m1
System.out.println(f2.get()); // 进行了输出m2
executor.shutdown();
System.out.println( "主线程执行完了" );
Long time2 = TimeUnit.MILLISECONDS.toSeconds(System.currentTimeMillis());
System.out.println( "主线程等待了" + (time2 - time1) + "秒" );
}
} |
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class MyTread implements Callable<String> {
@Override
public String call() {
try {
System.out.println( "线程调度:" + Thread.currentThread());
TimeUnit.SECONDS.sleep( 3 );
} catch (InterruptedException e) {
e.printStackTrace();
}
return "123" ;
}
} class MyTread2 implements Callable<String> {
@Override
public String call() {
try {
System.out.println( "线程调度2:" + Thread.currentThread());
TimeUnit.SECONDS.sleep( 3 );
} catch (InterruptedException e) {
e.printStackTrace();
}
return "abc" ;
}
} |
当不对m1和m2做输出时,main和m1、m2并发执行,当对m1和m2中任意一个的返回值进行处理的时候,main需要等待,但是m1和m2之前仍然是并发执行,执行结果如下:
线程调度2:Thread[pool-1-thread-2,5,main]
线程调度:Thread[pool-1-thread-1,5,main]
123
abc
主线程执行完了
主线程等待了3秒