[学习交流] hashmap线程不安全

API说明：(The HashMap class is roughly equivalent to Hashtable, except that it is unsynchronized and permits nulls）

public class ShareData1 {
//static int data = 0;
static Map<Thread,Integer> map = new HashMap<Thread,Integer>();
public static void main(String[] args) {
for(int i=0;i<2;i++){
new Thread(){
public void run() {
int data = new Random().nextInt();
System.out.println(Thread.currentThread().getName()+":"+data);
map.put(Thread.currentThread(), data);
/* map.put(Thread.currentThread(), data);
System.out.println(Thread.currentThread().getName()+":"+data);*/
new A().getDataA();
new B().getDataB();
};
}.start();
}
}
static class A{
void getDataA(){
System.out.println(Thread.currentThread().getName()+"A:"+map.get(Thread.currentThread()));
}}
static class B{
void getDataB(){
System.out.println(Thread.currentThread().getName()+"B:"+map.get(Thread.currentThread()));
}}
}
/*错误的结果:
Thread-1:-236229789
Thread-0:-934142735
Thread-1A:null
Thread-0A:-934142735
Thread-1B:null
Thread-0B:-934142735
=====================
Thread-0:-1331897743
Thread-1:-1239048981
Thread-1A:-1239048981
Thread-0A:null
Thread-1B:-1239048981
Thread-0B:null
====================
Thread-0:-1192204428
Thread-1:-439715298
Thread-0A:null
Thread-1A:-439715298
Thread-0B:null
Thread-1B:-439715298
******************************************************
正确的结果
Thread-0:1109365405
Thread-1:969714427
Thread-0A:1109365405
Thread-1A:969714427
Thread-0B:1109365405
Thread-1B:969714427
===================
Thread-1:1936099369
Thread-0:-616837039
Thread-0A:-616837039
Thread-1A:1936099369
Thread-0B:-616837039
Thread-1B:1936099369
*/

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