java 线程隐含同步错误 包装类

package com.test;import java.util.ArrayList;import java.util.List;import java.util.concurrent.Callable;import java.util.concurrent.CompletionService;import java.util.concurrent.ExecutionException;import java.util.concurrent.ExecutorCompletionService;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import java.util.concurrent.Future;public class ManyFileUpload {private static Integer num = 0;public static int getInt() {synchronized (num) {//这样的线程同步是有问题的 因为每一次num在++后都是新对象了具体参见包装类return ++num;}}public static void main(String[] args) throws InterruptedException,ExecutionException {ExecutorService pool = Executors.newCachedThreadPool();List<Callable<Integer>> list = new ArrayList<Callable<Integer>>();int all[] = new int[101];for(int i : all){i = 1;//不起作用}for(int i : all){System.out.println(i);}System.out.println("========================");for (int i = 0; i < 100; i++) {list.add(new Callable<Integer>() {@Overridepublic Integer call() throws Exception {return ++num;}});}List<Future<Integer>> futures = pool.invokeAll(list);for (Future f : futures) {int i = (Integer) f.get();all[i]++;System.out.println(i);}System.out.println("========================");for(int i=0;i<100;i++){System.out.println(i+":"+all[i]);}pool.shutdown();}}

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