Android多线程操作——线程池管理综述
1、简述：
在多线程的世界中，是那么的神奇 与 高效以及合理；
2、创建线程池实例
官方推荐使用Executors类工厂方法来创建线程池管理，Executors类是官方提供的一个工厂类，里面封装了好多功能不一样的线程池，从而使得我们创建线程池非常的简单：
3、使用线程池来管理任务
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4、Executors核心创建说明
可以看到1 - 3 创建线程池的方法中，全部是创建了ThreadPoolExecutor这个对象实例，不同的只是构造中的参数不一至，而在4 与5 ，从其继承的角度来看
public class ScheduledThreadPoolExecutor
extends ThreadPoolExecutor
implements ScheduledExecutorService {
可以看到其实质也是继承于ThreadPoolExecutor这个对象实例。
也就是说上述一种类型的线程池其都是 ThreadPoolExecutor子类，其实直接创建ThreadPoolExecutor实例对象，只需要传入相对应的配制参数，就可以创建出来与上述五种效果相一至的线程池管理，只不过是在书写的时候太过于繁锁。
/**
* Creates a new {@code ThreadPoolExecutor} with the given initial
* parameters and default thread factory and rejected execution handler.
* It may be more convenient to use one of the {@link Executors} factory
* methods instead of this general purpose constructor.
*
* @param corePoolSize the number of threads to keep in the pool, even
* if they are idle, unless {@code allowCoreThreadTimeOut} is set
* @param maximumPoolSize the maximum number of threads to allow in the
* pool
* @param keepAliveTime when the number of threads is greater than
* the core, this is the maximum time that excess idle threads
* will wait for new tasks before terminating.
* @param unit the time unit for the {@code keepAliveTime} argument
* @param workQueue the queue to use for holding tasks before they are
* executed. This queue will hold only the {@code Runnable}
* tasks submitted by the {@code execute} method.
* @throws IllegalArgumentException if one of the following holds:
* {@code corePoolSize < 0}
* {@code keepAliveTime < 0}
* {@code maximumPoolSize <= 0}
* {@code maximumPoolSize < corePoolSize}
* @throws NullPointerException if {@code workQueue} is null
*/
public ThreadPoolExecutor(int corePoolSize,
int maximumPoolSize,
long keepAliveTime,
TimeUnit unit,
BlockingQueue workQueue) {
this(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue,
Executors.defaultThreadFactory(), defaultHandler);
}
5、ThreadPoolExecutor简述
从上述创建ThreadPoolEecutor实例的构造来说，
6、自定义线程池
/**
* 创建线程池也是需要资源的，所以线程池内线程数量的大小也会影响系统的性能，
* 大了反而浪费资源，小了反而影响系统的吞吐量，
* 所以我们创建线程池需要把握一个度才能合理的发挥它的优点，
* 通常来说我们要考虑的因素有CPU的数量、内存的大小、并发请求的数量等因素，按需调整。
*通常核心线程数可以设为CPU数量+1，而最大线程数可以设为CPU的数量*2+1。
*/
private void customThreadFunction() {
/**
* 获取CPU数量
*/
int processors = Runtime.getRuntime().availableProcessors();
/**
* 核心线程数量
*/
int corePoolSize =processors + 1;
/**
* 最大线程数量
*/
int maximumPoolSize = processors * 2 + 1;
/**
* 空闲有效时间
*/
long keepAliveTime = 60;
/**
* 创建自定义线程池
*/
ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(corePoolSize, maximumPoolSize, keepAliveTime, TimeUnit.SECONDS, new PriorityBlockingQueue());
/**
* 添加执行任务
*/
for (int i=1;i<=20;i++){
final int prites = i;
threadPoolExecutor.execute(new CustomRunnable(prites){
@Override
public void doRun() {
String name = Thread.currentThread().getName();
System.out.println("curentThread name is "+name +"and prites is "+prites);
SystemClock.sleep(1000);
}
});
}
}
public abstract class CustomRunnable implements Runnable,Comparable{ private int priority; public CustomRunnable(int priority) { if (priority<0) throw new IllegalArgumentException(); this.priority = priority; } @Override public int compareTo(CustomRunnable another) { int my = this.getPriority(); int other = another.getPriority(); if (my>other){ return -1; }else{ return 0; } } @Override public void run() { doRun(); } public abstract void doRun(); public int getPriority() { return priority; } }
7、自定义扩展线程池：
public class CustomExpanThreadPool extends ThreadPoolExecutor {
private CustomExpanThreadPool(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue workQueue) {
super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue);
}
public static CustomExpanThreadPool getInstance() {
/**
* 获取CPU数量
*/
int processors = Runtime.getRuntime().availableProcessors();
/**
* 核心线程数量
*/
int corePoolSize = processors + 1;
/**
* 最大线程数量
*/
int maximumPoolSize = processors * 2 + 1;
/**
* 空闲有效时间
*/
long keepAliveTime = 60;
/**
* 创建自定义线程池
*/
return new CustomExpanThreadPool(corePoolSize, maximumPoolSize, keepAliveTime, TimeUnit.SECONDS, new PriorityBlockingQueue());
}
/**
* 用于控制线程开始与停止执行的方法
*/
private boolean isPaused;
private ReentrantLock pauseLock = new ReentrantLock();
private Condition unpaused = pauseLock.newCondition();
/**
* 任务执行前要执行的方法
*
* @param t
* @param r
*/
@Override
protected void beforeExecute(Thread t, Runnable r) {
super.beforeExecute(t, r);
System.out.println(Thread.currentThread().getName() + " 任务执行开始 ");
pauseLock.lock();
try {
while (isPaused) unpaused.await();
} catch (InterruptedException ie) {
t.interrupt();
} finally {
}
}
/**
* 任务执行后要执行的方法
*
* @param r
* @param t
*/
@Override
protected void afterExecute(Runnable r, Throwable t) {
super.afterExecute(r, t);
System.out.println(Thread.currentThread().getName() + " 任务执行over ");
}
/**
* 线程池关闭后要执行的方法
*/
@Override
protected void terminated() {
super.terminated();
}
/**
* 暂停执行任务的方法
*/
public void pause() {
pauseLock.lock();
try {
isPaused = true;
} finally {
pauseLock.unlock();
}
}
/**
* 恢复执行任务的方法
*/
public void resume() {
pauseLock.lock();
try {
isPaused = false;
unpaused.signalAll();
} finally {
pauseLock.unlock();
}
}
}
使用：
private void customThreadFunction2() {
CustomExpanThreadPool threadPoolExecutor = CustomExpanThreadPool.getInstance();
/**
* 添加执行任务
*/
for (int i=1;i<=20;i++){
final int prites = i;
threadPoolExecutor.execute(new CustomRunnable(prites){
@Override
public void doRun() {
String name = Thread.currentThread().getName();
System.out.println("curentThread name is "+name +"and prites is "+prites);
SystemClock.sleep(1000);
}
});
}
}
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