Executor框架是指java 5中引入的一系列并发库中与executor相关的一些功能类，其中包括线程池，Executor，Executors，ExecutorService，CompletionService，Future，Callable等。

Executor框架简介

Executor框架描述

Executor框架是指java 5中引入的一系列并发库中与executor相关的一些功能类，其中包括线程池，Executor，Executors，ExecutorService，CompletionService，Future，Callable等。

运用该框架能够很好的将任务分成一个个的子任务，使并发编程变得方便。

Executor相关类图

该框架的类图（方法并没有都表示出来）如下：

创建线程池类别

• 创建线程池 

Executors类，提供了一系列工厂方法用于创先线程池，返回的线程池都实现了ExecutorService接口。 

public static ExecutorService newFixedThreadPool(int nThreads) 

• 创建固定数目线程的线程池 

public static ExecutorService newCachedThreadPool() 

• 创建一个可缓存的线程池

创建一个可缓存的线程池，调用execute 将重用以前构造的线程（如果线程可用）。如果现有线程没有可用的，则创建一个新线程并添加到池中。终止并从缓存中移除那些已有 60 秒钟未被使用的线程。 

public static ExecutorService newSingleThreadExecutor() 

 

• 创建一个单线程化的Executor 

public static ScheduledExecutorService newScheduledThreadPool(int corePoolSize) 

创建一个支持定时及周期性的任务执行的线程池，多数情况下可用来替代Timer类。 

Executor框架使用案例

案例描述

本文主要是使用Executor框架来完成一个任务：求出10000个随机数据中的top 100。

Note:

本文只是用Executor来做一个例子，并不是用最好的办法去求10000个数中最大的100个数。 

过程描述

具体过程有如下4个步骤组成：

• 随机产生10000个数（范围1～9999），并存放在一个文件中。 
• 读取该文件的数值，并存放在一个数组中。 
• 采用Executor框架，进行并发操作，将10000个数据用10个线程来做，每个线程完成1000＝（10000/10）个数据的top 100操作。 
• 将10个线程返回的各个top 100数据，重新计算，得出最后的10000个数据的top 100。

代码思考和实现

随机产生数和读取随机数文件的类如下： 

import java.io.BufferedReader;import java.io.BufferedWriter;import java.io.File;import java.io.FileNotFoundException;import java.io.FileReader;import java.io.FileWriter;import java.io.IOException;import java.util.Random;/** *  * @author wangmengjun * */public class RandomUtil {	private static final int RANDOM_SEED = 10000;	private static final int SIZE = 10000;	/**	 * 产生10000万个随机数(范围1~9999)，并将这些数据添加到指定文件中去。	 * 	 * 例如：	 * 	 * 1=7016 2=7414 3=3117 4=6711 5=5569 ... ... 9993=1503 9994=9528 9995=9498	 * 9996=9123 9997=6632 9998=8801 9999=9705 10000=2900	 */	public static void generatedRandomNbrs(String filepath) {		Random random = new Random();		BufferedWriter bw = null;		try {			bw = new BufferedWriter(new FileWriter(new File(filepath)));			for (int i = 0; i < SIZE; i++) {				bw.write((i + 1) + "=" + random.nextInt(RANDOM_SEED));				bw.newLine();			}		} catch (IOException e) {			// TODO Auto-generated catch block			e.printStackTrace();		} finally {			if (null != bw) {				try {					bw.close();				} catch (IOException e) {					// TODO Auto-generated catch block					e.printStackTrace();				}			}		}	}	/**	 * 从指定文件中提取已经产生的随机数集	 */	public static int[] populateValuesFromFile(String filepath) {		BufferedReader br = null;		int[] values = new int[SIZE];		try {			br = new BufferedReader(new FileReader(new File(filepath)));			int count = 0;			String line = null;			while (null != (line = br.readLine())) {				values[count++] = Integer.parseInt(line.substring(line						.indexOf("=") + 1));			}		} catch (FileNotFoundException e) {			// TODO Auto-generated catch block			e.printStackTrace();		} catch (NumberFormatException e) {			// TODO Auto-generated catch block			e.printStackTrace();		} catch (IOException e) {			// TODO Auto-generated catch block			e.printStackTrace();		} finally {			if (null != br) {				try {					br.close();				} catch (IOException e) {					// TODO Auto-generated catch block					e.printStackTrace();				}			}		}		return values;	}}

编写一个Calculator 类， 实现Callable接口，计算指定数据集范围内的top 100。

import java.util.Arrays;import java.util.concurrent.Callable;/** *  * @author wangmengjun * */public class Calculator implements Callable
    
      {	/** 待处理的数据 */	private int[] values;	/** 起始索引 */	private int startIndex;	/** 结束索引 */	private int endIndex;	/**	 * @param values	 * @param startIndex	 * @param endIndex	 */	public Calculator(int[] values, int startIndex, int endIndex) {		this.values = values;		this.startIndex = startIndex;		this.endIndex = endIndex;	}	public Integer[] call() throws Exception {		// 将指定范围的数据复制到指定的数组中去		int[] subValues = new int[endIndex - startIndex + 1];		System.arraycopy(values, startIndex, subValues, 0, endIndex				- startIndex + 1);		Arrays.sort(subValues);		// 将排序后的是数组数据，取出top 100 并返回。		Integer[] top100 = new Integer[100];		for (int i = 0; i < 100; i++) {			top100[i] = subValues[subValues.length - i - 1];		}		return top100;	}	/**	 * @return the values	 */	public int[] getValues() {		return values;	}	/**	 * @param values	 *            the values to set	 */	public void setValues(int[] values) {		this.values = values;	}	/**	 * @return the startIndex	 */	public int getStartIndex() {		return startIndex;	}	/**	 * @param startIndex	 *            the startIndex to set	 */	public void setStartIndex(int startIndex) {		this.startIndex = startIndex;	}	/**	 * @return the endIndex	 */	public int getEndIndex() {		return endIndex;	}	/**	 * @param endIndex	 *            the endIndex to set	 */	public void setEndIndex(int endIndex) {		this.endIndex = endIndex;	}}
    

使用CompletionService实现 

import java.util.Arrays;import java.util.concurrent.ExecutionException;import java.util.concurrent.ExecutorCompletionService;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;/** *  * @author wangmengjun * */public class ConcurrentCalculator {	private ExecutorService exec;	private ExecutorCompletionService
    
      completionService;	private int availableProcessors = 0;	public ConcurrentCalculator() {		/*		 * 获取可用的处理器数量，并根据这个数量指定线程池的大小。		 */		availableProcessors = populateAvailableProcessors();		exec = Executors.newFixedThreadPool(availableProcessors);		completionService = new ExecutorCompletionService
     
      (exec);	}	/**	 * 获取10000个随机数中top 100的数。	 */	public Integer[] top100(int[] values) {		/*		 * 用十个线程，每个线程处理1000个。		 */		for (int i = 0; i < 10; i++) {			completionService.submit(new Calculator(values, i * 1000,					i * 1000 + 1000 - 1));		}		shutdown();		return populateTop100();	}	/**	 * 计算top 100的数。	 * 	 * 计算方法如下： 1. 初始化一个top 100的数组，数值都为0，作为当前的top 100. 2. 将这个当前的top	 * 100数组依次与每个线程产生的top 100数组比较，调整当前top 100的值。	 * 	 */	private Integer[] populateTop100() {		Integer[] top100 = new Integer[100];		for (int i = 0; i < 100; i++) {			top100[i] = new Integer(0);		}		for (int i = 0; i < 10; i++) {			try {				adjustTop100(top100, completionService.take().get());			} catch (InterruptedException e) {				e.printStackTrace();			} catch (ExecutionException e) {				e.printStackTrace();			}		}		return top100;	}	/**	 * 将当前top 100数组和一个线程返回的top 100数组比较，并调整当前top 100数组的数据。	 */	private void adjustTop100(Integer[] currentTop100, Integer[] subTop100) {		Integer[] currentTop200 = new Integer[200];		System.arraycopy(currentTop100, 0, currentTop200, 0, 100);		System.arraycopy(subTop100, 0, currentTop200, 100, 100);		Arrays.sort(currentTop200);		for (int i = 0; i < currentTop100.length; i++) {			currentTop100[i] = currentTop200[currentTop200.length - i - 1];		}	}	/**	 * 关闭 executor	 */	public void shutdown() {		exec.shutdown();	}	/**	 * 返回可以用的处理器个数	 */	private int populateAvailableProcessors() {		return Runtime.getRuntime().availableProcessors();	}}
     
    

使用Callable，Future计算结果 

import java.util.ArrayList;import java.util.Arrays;import java.util.List;import java.util.concurrent.ExecutionException;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import java.util.concurrent.Future;import java.util.concurrent.FutureTask;/** *  * @author wangmengjun * */public class ConcurrentCalculator2 {	private List
    
     
      > tasks = new ArrayList
      
       
        >();	private ExecutorService exec;	private int availableProcessors = 0;	public ConcurrentCalculator2() {		/*		 * 获取可用的处理器数量，并根据这个数量指定线程池的大小。		 */		availableProcessors = populateAvailableProcessors();		exec = Executors.newFixedThreadPool(availableProcessors);	}	/**	 * 获取10000个随机数中top 100的数。	 */	public Integer[] top100(int[] values) {		/*		 * 用十个线程，每个线程处理1000个。		 */		for (int i = 0; i < 10; i++) {			FutureTask
        
          task = new FutureTask
         
          ( new Calculator(values, i * 1000, i * 1000 + 1000 - 1)); tasks.add(task); if (!exec.isShutdown()) { exec.submit(task); } } shutdown(); return populateTop100(); } /** * 计算top 100的数。 * * 计算方法如下： 1. 初始化一个top 100的数组，数值都为0，作为当前的top 100. 2. 将这个当前的top * 100数组依次与每个Task产生的top 100数组比较，调整当前top 100的值。 * */ private Integer[] populateTop100() { Integer[] top100 = new Integer[100]; for (int i = 0; i < 100; i++) { top100[i] = new Integer(0); } for (Future
          
            task : tasks) { try { adjustTop100(top100, task.get()); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (ExecutionException e) { // TODO Auto-generated catch block e.printStackTrace(); } } return top100; } /** * 将当前top 100数组和一个线程返回的top 100数组比较，并调整当前top 100数组的数据。 */ private void adjustTop100(Integer[] currentTop100, Integer[] subTop100) { Integer[] currentTop200 = new Integer[200]; System.arraycopy(currentTop100, 0, currentTop200, 0, 100); System.arraycopy(subTop100, 0, currentTop200, 100, 100); Arrays.sort(currentTop200); for (int i = 0; i < currentTop100.length; i++) { currentTop100[i] = currentTop200[currentTop200.length - i - 1]; } } /** * 关闭executor */ public void shutdown() { exec.shutdown(); } /** * 返回可以用的处理器个数 */ private int populateAvailableProcessors() { return Runtime.getRuntime().availableProcessors(); }}
          
         
        
       
      
     
    

测试

测试包括了三部分： 

1. 没有用Executor框架，用Arrays.sort直接计算，并从后往前取100个数。 
2. 使用CompletionService计算结果 
3. 使用Callable和Future计算结果 

import java.util.Arrays;public class Test {	private static final String FILE_PATH = "D:\\RandomNumber.txt";	public static void main(String[] args) {		test();	}	private static void test() {		/**		 * 如果随机数已经存在文件中，可以不再调用此方法，除非想用新的随机数据。		 */		generateRandomNbrs();		process1();		process2();		process3();	}	private static void generateRandomNbrs() {		RandomUtil.generatedRandomNbrs(FILE_PATH);	}	private static void process1() {		long start = System.currentTimeMillis();		System.out.println("没有使用Executor框架，直接使用Arrays.sort获取top 100");		printTop100(populateTop100(RandomUtil.populateValuesFromFile(FILE_PATH)));		long end = System.currentTimeMillis();		System.out.println((end - start) / 1000.0);	}	private static void process2() {		long start = System.currentTimeMillis();		System.out.println("使用ExecutorCompletionService获取top 100");		ConcurrentCalculator calculator = new ConcurrentCalculator();		Integer[] top100 = calculator.top100(RandomUtil				.populateValuesFromFile(FILE_PATH));		for (int i = 0; i < top100.length; i++) {			System.out.println(String.format("top%d = %d", (i + 1), top100[i]));		}		long end = System.currentTimeMillis();		System.out.println((end - start) / 1000.0);	}	private static void process3() {		long start = System.currentTimeMillis();		System.out.println("使用FutureTask 获取top 100");		ConcurrentCalculator2 calculator2 = new ConcurrentCalculator2();		Integer[] top100 = calculator2.top100(RandomUtil				.populateValuesFromFile(FILE_PATH));		for (int i = 0; i < top100.length; i++) {			System.out.println(String.format("top%d = %d", (i + 1), top100[i]));		}		long end = System.currentTimeMillis();		System.out.println((end - start) / 1000.0);	}	private static int[] populateTop100(int[] values) {		Arrays.sort(values);		int[] top100 = new int[100];		int length = values.length;		for (int i = 0; i < 100; i++) {			top100[i] = values[length - 1 - i];		}		return top100;	}	private static void printTop100(int[] top100) {		for (int i = 0; i < top100.length; i++) {			System.out.println(String.format("top%d = %d", (i + 1), top100[i]));		}	}}

某次运行结果如下：

没有使用Executor框架，直接使用Arrays.sort获取top 100top1 = 9998top2 = 9995top3 = 9994top4 = 9989top5 = 9989top6 = 9989top7 = 9987top8 = 9985top9 = 9984top10 = 9982top11 = 9982top12 = 9981top13 = 9979top14 = 9978top15 = 9977top16 = 9975top17 = 9974top18 = 9974top19 = 9973top20 = 9973top21 = 9971top22 = 9971top23 = 9970top24 = 9970top25 = 9970top26 = 9969top27 = 9969top28 = 9967top29 = 9966top30 = 9965top31 = 9965top32 = 9965top33 = 9963top34 = 9963top35 = 9962top36 = 9961top37 = 9960top38 = 9960top39 = 9960top40 = 9960top41 = 9959top42 = 9958top43 = 9956top44 = 9955top45 = 9954top46 = 9952top47 = 9951top48 = 9950top49 = 9948top50 = 9948top51 = 9945top52 = 9944top53 = 9944top54 = 9939top55 = 9939top56 = 9938top57 = 9936top58 = 9936top59 = 9936top60 = 9935top61 = 9933top62 = 9933top63 = 9932top64 = 9929top65 = 9929top66 = 9925top67 = 9924top68 = 9923top69 = 9923top70 = 9922top71 = 9921top72 = 9921top73 = 9919top74 = 9919top75 = 9918top76 = 9913top77 = 9912top78 = 9911top79 = 9911top80 = 9911top81 = 9908top82 = 9906top83 = 9905top84 = 9905top85 = 9904top86 = 9904top87 = 9903top88 = 9901top89 = 9901top90 = 9900top91 = 9900top92 = 9899top93 = 9899top94 = 9898top95 = 9898top96 = 9897top97 = 9896top98 = 9895top99 = 9892top100 = 98920.067使用ExecutorCompletionService获取top 100top1 = 9998top2 = 9995top3 = 9994top4 = 9989top5 = 9989top6 = 9989top7 = 9987top8 = 9985top9 = 9984top10 = 9982top11 = 9982top12 = 9981top13 = 9979top14 = 9978top15 = 9977top16 = 9975top17 = 9974top18 = 9974top19 = 9973top20 = 9973top21 = 9971top22 = 9971top23 = 9970top24 = 9970top25 = 9970top26 = 9969top27 = 9969top28 = 9967top29 = 9966top30 = 9965top31 = 9965top32 = 9965top33 = 9963top34 = 9963top35 = 9962top36 = 9961top37 = 9960top38 = 9960top39 = 9960top40 = 9960top41 = 9959top42 = 9958top43 = 9956top44 = 9955top45 = 9954top46 = 9952top47 = 9951top48 = 9950top49 = 9948top50 = 9948top51 = 9945top52 = 9944top53 = 9944top54 = 9939top55 = 9939top56 = 9938top57 = 9936top58 = 9936top59 = 9936top60 = 9935top61 = 9933top62 = 9933top63 = 9932top64 = 9929top65 = 9929top66 = 9925top67 = 9924top68 = 9923top69 = 9923top70 = 9922top71 = 9921top72 = 9921top73 = 9919top74 = 9919top75 = 9918top76 = 9913top77 = 9912top78 = 9911top79 = 9911top80 = 9911top81 = 9908top82 = 9906top83 = 9905top84 = 9905top85 = 9904top86 = 9904top87 = 9903top88 = 9901top89 = 9901top90 = 9900top91 = 9900top92 = 9899top93 = 9899top94 = 9898top95 = 9898top96 = 9897top97 = 9896top98 = 9895top99 = 9892top100 = 98920.025使用FutureTask 获取top 100top1 = 9998top2 = 9995top3 = 9994top4 = 9989top5 = 9989top6 = 9989top7 = 9987top8 = 9985top9 = 9984top10 = 9982top11 = 9982top12 = 9981top13 = 9979top14 = 9978top15 = 9977top16 = 9975top17 = 9974top18 = 9974top19 = 9973top20 = 9973top21 = 9971top22 = 9971top23 = 9970top24 = 9970top25 = 9970top26 = 9969top27 = 9969top28 = 9967top29 = 9966top30 = 9965top31 = 9965top32 = 9965top33 = 9963top34 = 9963top35 = 9962top36 = 9961top37 = 9960top38 = 9960top39 = 9960top40 = 9960top41 = 9959top42 = 9958top43 = 9956top44 = 9955top45 = 9954top46 = 9952top47 = 9951top48 = 9950top49 = 9948top50 = 9948top51 = 9945top52 = 9944top53 = 9944top54 = 9939top55 = 9939top56 = 9938top57 = 9936top58 = 9936top59 = 9936top60 = 9935top61 = 9933top62 = 9933top63 = 9932top64 = 9929top65 = 9929top66 = 9925top67 = 9924top68 = 9923top69 = 9923top70 = 9922top71 = 9921top72 = 9921top73 = 9919top74 = 9919top75 = 9918top76 = 9913top77 = 9912top78 = 9911top79 = 9911top80 = 9911top81 = 9908top82 = 9906top83 = 9905top84 = 9905top85 = 9904top86 = 9904top87 = 9903top88 = 9901top89 = 9901top90 = 9900top91 = 9900top92 = 9899top93 = 9899top94 = 9898top95 = 9898top96 = 9897top97 = 9896top98 = 9895top99 = 9892top100 = 98920.013