java.util.Stack是线程安全的么

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package test;

import java.util.HashMap;
import java.util.Hashtable;
import java.util.concurrent.CountDownLatch;

public class HashTbAndHashMap {

public static void main(String[] args) {

for (int i = 0; i < 10; i++) {
//testHashMap();
testHashTable();
}
}

public static void testHashMap() {

HashMap map = new HashMap();

int nbthread = 1000;

CountDownLatch countDownLatch = new CountDownLatch(nbthread);

for (int i = 0; i < nbthread; i++) {
Thread thread = new Thread(new MyThread(map, countDownLatch));
thread.start();
}

try {
countDownLatch.await();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

System.out.println(map.size());
}

public static void testHashTable() {

Hashtable table = new Hashtable();

int nbthread = 1000;

CountDownLatch countDownLatch = new CountDownLatch(nbthread);

for (int i = 0; i < nbthread; i++) {
Thread thread = new Thread(new MyThread(table, countDownLatch));
thread.start();
}

try {
countDownLatch.await();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

System.out.println(table.size());
}
}

=======================
package test;

import java.util.HashMap;
import java.util.Hashtable;
import java.util.concurrent.CountDownLatch;

public class MyThread implements Runnable {

private HashMap map;

private Hashtable table;

private CountDownLatch countDownLatch;

public MyThread(HashMap map, CountDownLatch countDownLatch) {
this.map = map;
this.countDownLatch = countDownLatch;
}

public MyThread(Hashtable table,
CountDownLatch countDownLatch) {
this.table = table;
this.countDownLatch = countDownLatch;
}

@Override
public void run() {
for (int i = 0; i < 100; i++) {
table.put(i, i);
//map.put(i, i);
}
countDownLatch.countDown();
}

}

你执行一下就看出来区别了