Guava ---- Concurrent并发

  Guava在JDK1.5的基础上， 对并发包进行扩展， 有一些是易用性的扩展（如Monitor）， 有一些是功能的完善（如ListenableFuture）， 再加上一些函数式编程的特性， 使并发包的灵活性极大的提高...

Monitor的使用：

import com.google.common.util.concurrent.Monitor;import java.util.ArrayList;import java.util.Iterator;import java.util.List;import java.util.concurrent.atomic.AtomicBoolean;/** * Monitor类语义和 synchronized 或者 ReentrantLocks是一样的， 只允许一个线程进入 */public class MonitorSample {    private static final int MAX_SIZE = 3;    private Monitor monitor = new Monitor();    private List<String> list = new ArrayList<String>();    Monitor.Guard listBelowCapacity = new            Monitor.Guard(monitor) {                @Override                public boolean isSatisfied() {                    return list.size() < MAX_SIZE;                }            };    public void addToList(String item) throws InterruptedException {        // 超过MAX_SIZE， 会锁死        //monitor.enterWhen(listBelowCapacity);        // 超过返回false  不会锁死        Boolean a = monitor.tryEnterIf(listBelowCapacity);        try {            list.add(item);        } finally { // 确保线程会推出Monitor锁            monitor.leave();        }    }    public static void main(String[] args) {        MonitorSample monitorSample = new MonitorSample();        for (int count = 0; count < 5; count++) {            try {                monitorSample.addToList(count + "");            }            catch (Exception e) {                System.out.println(e);            }        }        Iterator iteratorStringList = monitorSample.list.iterator();        while (iteratorStringList.hasNext()) {            System.out.println(iteratorStringList.next());        }    }}

Future的扩展： 可识别的返回结果， 可改变的返回结果

package com.wenniuwuren.listenablefuture;import java.util.concurrent.Callable;import java.util.concurrent.ExecutionException;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import java.util.concurrent.Future;import com.google.common.util.concurrent.FutureCallback;import com.google.common.util.concurrent.Futures;import com.google.common.util.concurrent.ListenableFuture;import com.google.common.util.concurrent.MoreExecutors;/** * 在使用ListenableFuture前， 最好看下JDK的Future使用 *  * @author wenniuwuren * */public class ListenableFutureTest {public static void main(String[] args) {        // Guava封装后带有执行结束监听任务执行结束的功能ExecutorService executorService =MoreExecutors.listeningDecorator(Executors.newFixedThreadPool(5));ListenableFuture<String> listenableFuture = (ListenableFuture<String>) executorService.submit(new Callable<String>() {public String call() throws Exception {return "task success ";}});/* Futrue初始版本 // JDK 自带线程池//ExecutorService executor = Executors.newCachedThreadPool();// JDK FutureFuture<Integer> future = executor.submit(new Callable<Integer>() {public Integer call() throws Exception {return 1;}});// JDK Future真正获取结果的地方try {Integer count = future.get();} catch (Exception e) {e.printStackTrace();}*//* listenableFuture 结束监听版本// 相比JDK的Future等待结果， Guava采用监听器在任务完成时调用// 但是有个缺陷， 对最后完成的结果没法对操作成功/失败进行处理， 即run方法没返回值listenableFuture.addListener(new Runnable() {@Overridepublic void run() {System.out.println("运行完成");}}, executorService);*/// 运行成功，将会返回 "task success successfully"  解决了listenableFuture 结束监听版本不能对结果进行操作问题FutureCallbackImpl callback = new FutureCallbackImpl();// 和计算结果同步运行//Futures.addCallback(listenableFuture, callback);//如果计算较大， 结果的访问使用异步  将会使用executorService线程去异步执行Futures.addCallback(listenableFuture, callback, executorService);System.out.println(callback.getCallbackResult());}}class FutureCallbackImpl implements FutureCallback<String> {private StringBuilder builder = new StringBuilder();@Overridepublic void onSuccess(String result) {builder.append(result).append("successfully");}@Overridepublic void onFailure(Throwable t) {builder.append(t.toString());}public String getCallbackResult() {return builder.toString();}}