JAVA进阶-多线程(3)

1.以前使用线程API并没有返回结果,Callable/Future/FutureTask正是解决了此问题,并在调用过程中

作出对异常的捕获

-Callable执行call()方法返回Object对象,也可抛出异常;调用
Callable并不像Thread,而是调用<T> Future ExecutorService.submit(Callable<T> task);
-Future 返回值,调用该接口的get()方法,可返回对应的对象
------------------

SalesCalculateSample.java>通过多线程计算矩阵每行结果并叠加;

/** * * @author Lean  @date:2014-9-30   */public class SalesCalculateSample {private static final int NUMBER_OF_MONTH=12;private static final int NUMBER_OF_CUSTOMER=100;private static int[][] cells;static class Summer implements Callable<Integer>{public int customerID;public Summer(int companyId){this.customerID=companyId;}@Overridepublic Integer call() throws Exception {int sum=0;for (int i = 0; i < NUMBER_OF_MONTH; i++) {sum+=cells[customerID][i];}System.out.printf("customerID:%d ,sum:%d\n",customerID,sum);return sum;}}public static void main(String[] args) {generateMatrix();ExecutorService executor=Executors.newFixedThreadPool(10);Set<Future<Integer>> futures=new HashSet<Future<Integer>>();for (int i = 0; i < NUMBER_OF_CUSTOMER; i++) {Callable<Integer> caller=new Summer(i);futures.add(executor.submit(caller));}// caculate the sumint sum=0;for (Future<Integer> future : futures) {try {sum+=future.get();} catch (Exception e) {e.printStackTrace();} }System.out.println("sum is>>"+sum);executor.shutdown();}private static void generateMatrix() {cells=new int[NUMBER_OF_CUSTOMER][NUMBER_OF_MONTH];for (int i = 0; i < NUMBER_OF_CUSTOMER; i++) {for (int j = 0; j < NUMBER_OF_MONTH; j++) {cells[i][j]=(int)(Math.random()*100);}}}}

------------------

------------------

CanCancelProcessors>随机取消提交的订单(Future提供了可取消的结果执行)

/** * * @author Lean  @date:2014-10-7   */public class CanCancelProcessors {private static ExecutorService service=Executors.newFixedThreadPool(100);private static final int ORDERS_COUNT=2000;private static ArrayList<Future<Integer>> futures=new ArrayList<Future<Integer>>();public static void main(String[] args) {for (int i = 0; i <ORDERS_COUNT; i++) {futures.add(service.submit(new OrderExcutor(i)));}new Thread(new EvilThread(futures)).start();try {service.awaitTermination(6,TimeUnit.SECONDS);} catch (InterruptedException e) {e.printStackTrace();}int count=0;for (Future<Integer> future : futures) {if (future.isCancelled()) {count++;}}System.out.println("----------"+count+" orders canceled!---------");service.shutdown();}static class OrderExcutor implements Callable<Integer>{private int mId;public OrderExcutor(int id){this.mId=id;}@Overridepublic Integer call() throws Exception {try {Thread.sleep(1000);} catch (InterruptedException e) {}System.out.println("successfully execute orderid : "+mId);return mId;}}static class EvilThread implements Runnable{private ArrayList<Future<Integer>> futures;public EvilThread(ArrayList<Future<Integer>> futures){this.futures=futures;}@Overridepublic void run() {for (int i = 0; i < ORDERS_COUNT; i++) {try {Thread.sleep(200);boolean flag=futures.get(i).cancel(true);System.out.println("cancel order >"+flag +" by id>> "+i);} catch (InterruptedException e) {}}}}}

------------------

-FutureTask 集成了Runnable与Future接口的功能,因此拥有异步,返回数据的功能;
------------------

FutureTaskSample

/** * * @author Lean  @date:2014-9-30   */public class FutureTaskSample {private static final int NUMBER_OF_MONTH=12;private static final int NUMBER_OF_CUSTOMER=100;private static int[][] cells;static class Summer implements Callable<Integer>{public int customerID;public Summer(int companyId){this.customerID=companyId;}@Overridepublic Integer call() throws Exception {int sum=0;for (int i = 0; i < NUMBER_OF_MONTH; i++) {sum+=cells[customerID][i];}System.out.printf("customerID:%d ,sum:%d\n",customerID,sum);return sum;}}public static void main(String[] args) {generateMatrix();Set<FutureTask<Integer>> futures=new HashSet<FutureTask<Integer>>();for (int i = 0; i < NUMBER_OF_CUSTOMER; i++) {Callable<Integer> caller=new Summer(i);FutureTask<Integer> futureTask=new FutureTask<Integer>(caller);futureTask.run();futures.add(futureTask);}// caculate the sumint sum=0;for (FutureTask<Integer> future : futures) {try {sum+=future.get();} catch (Exception e) {e.printStackTrace();} }System.out.println("sum is>>"+sum);}private static void generateMatrix() {cells=new int[NUMBER_OF_CUSTOMER][NUMBER_OF_MONTH];for (int i = 0; i < NUMBER_OF_CUSTOMER; i++) {for (int j = 0; j < NUMBER_OF_MONTH; j++) {cells[i][j]=(int)(Math.random()*100);}}}}

------------------
2.Executors
.newFixedThreadPool()创建固定线程池
.newCachedThreadPool()创建固定线程池,每个线程在60秒内不再创建
.newSingleThreadExecutor()创建单线程 该线程不会被销毁
.newScheduledExecutorService()创建可定时,延时执行的线程
------------------

ScheduledCountSample>定时,延时度取数字的例子

/** *ScheduledExecutorServiceSample * * @author Lean  @date:2014-10-7   */public class ScheduledCountSample {private static ScheduledExecutorService mService=Executors.newScheduledThreadPool(10);private static final int AVG=4;private static final int mAllCount=400;private static  int mCurrenCount=0;public static void main(String[] args) {//delay counting !//int times = mAllCount/AVG;//for (int i = 0; i < times; i++) {//mService.schedule(new tryCount(i), i*1,TimeUnit.SECONDS);//}//mService.scheduleAtFixedRate(new EveryCount(), 0, 1, TimeUnit.SECONDS);mService.scheduleWithFixedDelay(new EveryCount(), 0, 1, TimeUnit.SECONDS);}static class EveryCount implements Runnable{@Overridepublic void run() {if (mAllCount>mCurrenCount) {System.out.println("ThreadId>>"+Thread.currentThread().getId()+" and count >>"+mCurrenCount++);}}}static class tryCount implements Callable<Integer>{private int Index;public tryCount(int index) {this.Index=index;}@Overridepublic Integer call() throws Exception {for (int i = Index*AVG+0; i < (AVG+Index*AVG); i++) {System.out.println("count >>"+i);}System.out.println("thread count end! ");return Index;}}}

------------------

-ExecutorCompletionService
通常获取结果用get(),该方法形成阻塞.而通过take()获取已经结束的任务的结果

------------------
GetResultRightNow

/** * 获取非阻塞型结果 * * @author Lean  @date:2014-10-7   */public class GetResultRightNow {public static void main(String[] args) {int[] printNum={1000,200,200,30000,5000};ArrayList<Future<Integer>> fetures=new ArrayList<Future<Integer>>();ExecutorService executors = Executors.newFixedThreadPool(2);ExecutorCompletionService<Integer> service=new ExecutorCompletionService<Integer>(executors);for (int i : printNum) {fetures.add(service.submit(new getCurrnNum(i)));}try {executors.awaitTermination(5, TimeUnit.SECONDS);} catch (InterruptedException e) {e.printStackTrace();}for (int i = 0; i < printNum.length; i++) {int num=0;try {//take it when there has a result;num = service.take().get();//stop when there has no result no matter others having;//num=fetures.get(i).get();} catch (InterruptedException e) {e.printStackTrace();} catch (ExecutionException e) {e.printStackTrace();}System.out.println("num is:"+num);}executors.shutdown();}static class getCurrnNum implements Callable<Integer>{private int printNum;public getCurrnNum(int i) {printNum=i;}@Overridepublic Integer call() throws Exception {try {Thread.sleep(printNum);} catch (Exception e) {}return printNum;}}}

------------------