Java線程池的幾種實現(xiàn)方法和區(qū)別介紹實例詳解

import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import java.util.Random;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
public class TestThreadPool {
 // -newFixedThreadPool與cacheThreadPool差不多，也是能reuse就用，但不能隨時建新的線程
 // -其獨特之處:任意時間點，最多只能有固定數(shù)目的活動線程存在，此時如果有新的線程要建立，只能放在另外的隊列中等待，直到當(dāng)前的線程中某個線程終止直接被移出池子
 // -和cacheThreadPool不同，F(xiàn)ixedThreadPool沒有IDLE機制（可能也有，但既然文檔沒提，肯定非常長，類似依賴上層的TCP或UDP
 // IDLE機制之類的），所以FixedThreadPool多數(shù)針對一些很穩(wěn)定很固定的正規(guī)并發(fā)線程，多用于服務(wù)器
 // -從方法的源代碼看，cache池和fixed 池調(diào)用的是同一個底層池，只不過參數(shù)不同:
 // fixed池線程數(shù)固定，并且是0秒IDLE（無IDLE）
 // cache池線程數(shù)支持0-Integer.MAX_VALUE(顯然完全沒考慮主機的資源承受能力），60秒IDLE
 private static ExecutorService fixedService = Executors.newFixedThreadPool(6);
 // -緩存型池子，先查看池中有沒有以前建立的線程，如果有，就reuse.如果沒有，就建一個新的線程加入池中
 // -緩存型池子通常用于執(zhí)行一些生存期很短的異步型任務(wù)
 // 因此在一些面向連接的daemon型SERVER中用得不多。
 // -能reuse的線程，必須是timeout IDLE內(nèi)的池中線程，缺省timeout是60s,超過這個IDLE時長，線程實例將被終止及移出池。
 // 注意，放入CachedThreadPool的線程不必?fù)?dān)心其結(jié)束，超過TIMEOUT不活動，其會自動被終止。
 private static ExecutorService cacheService = Executors.newCachedThreadPool();
 // -單例線程，任意時間池中只能有一個線程
 // -用的是和cache池和fixed池相同的底層池，但線程數(shù)目是1-1,0秒IDLE（無IDLE）
 private static ExecutorService singleService = Executors.newSingleThreadExecutor();
 // -調(diào)度型線程池
 // -這個池子里的線程可以按schedule依次delay執(zhí)行，或周期執(zhí)行
 private static ExecutorService scheduledService = Executors.newScheduledThreadPool(10);
 public static void main(String[] args) {
 DateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
 List<Integer> customerList = new ArrayList<Integer>();
 System.out.println(format.format(new Date()));
 testFixedThreadPool(fixedService, customerList);
 System.out.println("--------------------------");
 testFixedThreadPool(fixedService, customerList);
 fixedService.shutdown();
 System.out.println(fixedService.isShutdown());
 System.out.println("----------------------------------------------------");
 testCacheThreadPool(cacheService, customerList);
 System.out.println("----------------------------------------------------");
 testCacheThreadPool(cacheService, customerList);
 cacheService.shutdownNow();
 System.out.println("----------------------------------------------------");
 testSingleServiceThreadPool(singleService, customerList);
 testSingleServiceThreadPool(singleService, customerList);
 singleService.shutdown();
 System.out.println("----------------------------------------------------");
 testScheduledServiceThreadPool(scheduledService, customerList);
 testScheduledServiceThreadPool(scheduledService, customerList);
 scheduledService.shutdown();
 } 
 public static void testScheduledServiceThreadPool(ExecutorService service, List<Integer> customerList) {
 List<Callable<Integer>> listCallable = new ArrayList<Callable<Integer>>();
 for (int i = 0; i < 10; i++) {
  Callable<Integer> callable = new Callable<Integer>() {
  @Override
  public Integer call() throws Exception {
   return new Random().nextInt(10);
  }
  };
  listCallable.add(callable);
 }
 try {
  List<Future<Integer>> listFuture = service.invokeAll(listCallable);
  for (Future<Integer> future : listFuture) {
  Integer id = future.get();
  customerList.add(id);
  }
 } catch (Exception e) {
  e.printStackTrace();
 }
 System.out.println(customerList.toString());
 }
 public static void testSingleServiceThreadPool(ExecutorService service, List<Integer> customerList) {
 List<Callable<List<Integer>>> listCallable = new ArrayList<Callable<List<Integer>>>();
 for (int i = 0; i < 10; i++) {
  Callable<List<Integer>> callable = new Callable<List<Integer>>() {
  @Override
  public List<Integer> call() throws Exception {
   List<Integer> list = getList(new Random().nextInt(10));
   boolean isStop = false;
   while (list.size() > 0 && !isStop) {
   System.out.println(Thread.currentThread().getId() + " -- sleep:1000");
   isStop = true;
   }
   return list;
  }
  };
  listCallable.add(callable);
 }
 try {
  List<Future<List<Integer>>> listFuture = service.invokeAll(listCallable);
  for (Future<List<Integer>> future : listFuture) {
  List<Integer> list = future.get();
  customerList.addAll(list);
  }
 } catch (Exception e) {
  e.printStackTrace();
 }
 System.out.println(customerList.toString());
 }
 public static void testCacheThreadPool(ExecutorService service, List<Integer> customerList) {
 List<Callable<List<Integer>>> listCallable = new ArrayList<Callable<List<Integer>>>();
 for (int i = 0; i < 10; i++) {
  Callable<List<Integer>> callable = new Callable<List<Integer>>() {
  @Override
  public List<Integer> call() throws Exception {
   List<Integer> list = getList(new Random().nextInt(10));
   boolean isStop = false;
   while (list.size() > 0 && !isStop) {
   System.out.println(Thread.currentThread().getId() + " -- sleep:1000");
   isStop = true;
   }
   return list;
  }
  };
  listCallable.add(callable);
 }
 try {
  List<Future<List<Integer>>> listFuture = service.invokeAll(listCallable);
  for (Future<List<Integer>> future : listFuture) {
  List<Integer> list = future.get();
  customerList.addAll(list);
  }
 } catch (Exception e) {
  e.printStackTrace();
 }
 System.out.println(customerList.toString());
 }
 public static void testFixedThreadPool(ExecutorService service, List<Integer> customerList) {
 List<Callable<List<Integer>>> listCallable = new ArrayList<Callable<List<Integer>>>();
 for (int i = 0; i < 10; i++) {
  Callable<List<Integer>> callable = new Callable<List<Integer>>() {
  @Override
  public List<Integer> call() throws Exception {
   List<Integer> list = getList(new Random().nextInt(10));
   boolean isStop = false;
   while (list.size() > 0 && !isStop) {
   System.out.println(Thread.currentThread().getId() + " -- sleep:1000");
   isStop = true;
   }
   return list;
  }
  };
  listCallable.add(callable);
 }
 try {
  List<Future<List<Integer>>> listFuture = service.invokeAll(listCallable);
  for (Future<List<Integer>> future : listFuture) {
  List<Integer> list = future.get();
  customerList.addAll(list);
  }
 } catch (Exception e) {
  e.printStackTrace();
 }
 System.out.println(customerList.toString());
 }
 public static List<Integer> getList(int x) {
 List<Integer> list = new ArrayList<Integer>();
 list.add(x);
 list.add(x * x);
 return list;
 }
}

//例如：corePoolSize=3,maximumPoolSize=6,LinkedBlockingQueue(10)
 
//RejectedExecutionHandler默認(rèn)處理方式是：ThreadPoolExecutor.AbortPolicy
 
//ThreadPoolExecutor executorService = new ThreadPoolExecutor(corePoolSize, maximumPoolSize, 1L, TimeUnit.SECONDS, new LinkedBlockingQueue<Runnable>(10));
 
//1.如果線程池中（也就是調(diào)用executorService.execute）運行的線程未達到LinkedBlockingQueue.init(10)的話，當(dāng)前執(zhí)行的線程數(shù)是:corePoolSize(3) 
 
//2.如果超過了LinkedBlockingQueue.init(10)并且超過的數(shù)>=init(10)+corePoolSize(3)的話，并且小于init(10)+maximumPoolSize. 當(dāng)前啟動的線程數(shù)是：(當(dāng)前線程數(shù)-init(10))
 
//3.如果調(diào)用的線程數(shù)超過了init(10)+maximumPoolSize 則根據(jù)RejectedExecutionHandler的規(guī)則處理。

//默認(rèn)使用：ThreadPoolExecutor.AbortPolicy，處理程序遭到拒絕將拋出運行時RejectedExecutionException。
      RejectedExecutionHandler policy=new ThreadPoolExecutor.AbortPolicy();
//     //在 ThreadPoolExecutor.CallerRunsPolicy 中，線程調(diào)用運行該任務(wù)的execute本身。此策略提供簡單的反饋控制機制，能夠減緩新任務(wù)的提交速度。
//     policy=new ThreadPoolExecutor.CallerRunsPolicy();
//     //在 ThreadPoolExecutor.DiscardPolicy 中，不能執(zhí)行的任務(wù)將被刪除。
//     policy=new ThreadPoolExecutor.DiscardPolicy();
//     //在 ThreadPoolExecutor.DiscardOldestPolicy 中，如果執(zhí)行程序尚未關(guān)閉，則位于工作隊列頭部的任務(wù)將被刪除，然后重試執(zhí)行程序（如果再次失敗，則重復(fù)此過程）。
//     policy=new ThreadPoolExecutor.DiscardOldestPolicy();