前言
做Android的这两年时间,通过研究Android源码,也会Java并发处理多线程有了自己的一些理解。
那么问题来了,如何实现一个串行的线程池呢?
思路
何为串行线程池呢?
也就是说,我们的Runnable对象应该有个排队的机制,它们顺序从队列尾部进入,并且从队列头部选择Runnable进行执行。
既然我们有了思路,那我们就考虑一下所需要的数据结构?
既然是从队列尾部插入Runnable对象,从队列头部执行Runnable对象,我们自然需要一个队列。Java的SDK已经给我们提供了很好的队列数据结构,例如双端队列:ArrayDeque<Runnable>。
- 因为涉及到线程的执行,那我们首先就需要有一个合适的线程池,使用ThreadPoolExecutor类即可构造。
- 既然是串行执行,那如何保持串行机制呢?我们可以通过try和finally机制,我们将传入的Runnable对象重新封装成一个新的Runnable对象,在新的Runnable的run方法的try块中执行Runnable的run方法,在finally中调用执行队列头部Runnable对象出队列,并放入线程池执行的方法。
示例代码
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
|
import java.util.ArrayDeque;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.LinkedBlockingDeque;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
/**
* Created by wzy on 16-1-5.
*/
public class SerialExecutor {
private Runnable mActive;
private ArrayDeque<Runnable> mArrayDeque = new ArrayDeque<>();
private static final int CPU_COUNT = Runtime.getRuntime().availableProcessors();
private static final int CORE_POOL_SIZE = CPU_COUNT + 1 ;
private static final int MAXIMUM_POOL_SIZE = CPU_COUNT * 2 + 1 ;
private static final int KEEP_ALIVE = 1 ;
private static final BlockingQueue<Runnable> sPoolWorkQueue =
new LinkedBlockingDeque<>( 128 );
private static final ThreadFactory sThreadFactory = new ThreadFactory() {
private final AtomicInteger mCount = new AtomicInteger( 1 );
@Override
public Thread newThread(Runnable r) {
return new Thread(r, "Serial thread #" + mCount.getAndIncrement());
}
};
private static final ThreadPoolExecutor THREAD_EXECUTOR = new ThreadPoolExecutor(CORE_POOL_SIZE,
MAXIMUM_POOL_SIZE, KEEP_ALIVE, TimeUnit.SECONDS, sPoolWorkQueue, sThreadFactory);
public synchronized void execute( final Runnable r) {
mArrayDeque.offer( new Runnable() {
@Override
public void run() {
try {
r.run();
} finally {
scheduleNext();
}
}
});
// 第一次入队列时mActivie为空,因此需要手动调用scheduleNext方法
if (mActive == null ) {
scheduleNext();
}
}
private void scheduleNext() {
if ((mActive = mArrayDeque.poll()) != null ) {
THREAD_EXECUTOR.execute(mActive);
}
}
public static void main(String[] args) {
SerialExecutor serialExecutor = new SerialExecutor();
for ( int i = 0 ; i < 10 ; i ++) {
final int j = i;
serialExecutor.execute( new Runnable() {
@Override
public void run() {
System.out.println( "The num is :" + (j + 1 ));
try {
Thread.sleep( 1000 );
} catch (InterruptedException e) {
e.printStackTrace();
}
}
});
}
}
}
|
执行结果如下:
The num is :1
The num is :2
The num is :3
The num is :4
The num is :5
The num is :6
The num is :7
The num is :8
The num is :9
The num is :10
总结
以上就是本文关于Java并发之串行线程池实例解析的全部内容,希望对大家有所帮助。感兴趣的朋友可以继续参阅本站其他相关专题,如有不足之处,欢迎留言指出。感谢朋友们对本站的支持!
原文链接:http://blog.csdn.net/wzy_1988/article/details/50461242