Java并发编程初探

package test;

import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.io.Reader;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;

public class Test {
    public static void getJavaFile(String currentpath,List<File> files){
        File dir = new File(currentpath);
        if(dir.exists()){
            File temp[] = dir.listFiles();
            if(temp != null)
            {            
                for (File b: temp) {
                    if (b.isFile() && b.toString().endsWith(".java")) {
                        files.add(b);
                    }
                    else if(b.isDirectory()){
                        getJavaFile(b.toString(), files);
                    }
                }
            }
        }
    }
    public final static float percent = (float) 0.9;
    public final static int poolsize = (int) (Runtime.getRuntime().availableProcessors()/(1-percent));
    public static void main(String[] args) throws Exception{
        // TODO Auto-generated method stub
        //初始化文件集合
        String path = "G:"+File.separator+"src";
        List<File> fs = new ArrayList<>();
        getJavaFile(path, fs);
        
        //顺序执行
        long start = System.currentTimeMillis();
        int total = 0;
        for(File s : fs){
            int i = getCount(s);
            //System.out.println(s.getName()+"长度为:"+i);
            total+=i;
        }
        long end = System.currentTimeMillis();
        System.out.println("顺序执行的时间:"+(end-start)+"得出来的结果:"+total);
        
        
        
        final ExecutorService executorpool = Executors.newFixedThreadPool(poolsize);
        final List<Callable<Integer>> partitions = new ArrayList<>();
        for(final File f1 : fs){
            partitions.add(new Callable<Integer>() {

                @Override
                public Integer call() throws Exception {
                    // TODO Auto-generated method stub
                    Integer i = getCount(f1);
                    //System.out.println(f1.getName()+"长度为:"+i);
                    return i;
                }
            });
        }
        long startbingfa = System.currentTimeMillis();
        final List<Future<Integer>> nums = executorpool.invokeAll(partitions,5,TimeUnit.MINUTES);
        int totalbingfa = 0;
        for(final Future<Integer>i : nums){
                totalbingfa = totalbingfa+i.get();
        }
        executorpool.shutdown();
        long endbingfa = System.currentTimeMillis();
        System.out.println("并发的时间:"+(endbingfa-startbingfa)+"得出来的结果:"+totalbingfa);

    }
    
    public static int getCount(File f) throws IOException{
        int count = 0;
        Reader br = new FileReader(f);
        //String line = "";
        int c;
        while ((c = br.read()) != -1) {
            if(‘a‘ == (char)c){
                count++;
            }
        }
        return count;
    }
}

final List<Callable<Integer>> partitions = new ArrayList<>();