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多线程和并发库应用五-线程间数据共享

2018-01-06 18:22 741 查看
本章主要讲述线程之间怎么实现数据共享

看下面一个例子

public class ThreadScopShareData {
public static int data=0;
public static void main(String[] args){
for (int i=0;i<2;i++)
new Thread(new Runnable() {
public void run() {
data=new Random().nextInt();
System.out.println(Thread.currentThread().getName()+" has put data: "+data);
new A().get();
new B().get();
}
}).start();
}
static  class A{
public int get(){
System.out.println(Thread.currentThread().getName()+" has A get data: "+data);
return data;
}
}
static  class B{
public int get(){
System.out.println(Thread.currentThread().getName()+" has B get data: "+data);
return data;
}
}
}


只用一个静态变量去存储数据然后创建两个线程分别设置值和取值发现运行结果如下

Thread-1 has put data: 823252219
Thread-1 has A get data: 823252219
Thread-0 has put data: 1753022753
Thread-0 has A get data: 1753022753
Thread-0 has B get data: 1753022753
Thread-1 has B get data: 1753022753


显然和预期的不一样。

改造一下将值存放在map 中

public class ThreadScopShareData {
public static int data=0;
static Map<String,Integer> map=new ConcurrentHashMap<String, Integer>();
public static void main(String[] args){
for (int i=0;i<2;i++)
new Thread(new Runnable() {
public void run() {
data=new Random().nextInt();
map.put(Thread.currentThread().getName(),data);
System.out.println(Thread.currentThread().getName()+" has put data: "+data);
new A().get();
new B().get();
}
}).start();
}
static  class A{
public int get(){
System.out.println(Thread.currentThread().getName()+" has A get data: "+map.get(Thread.currentThread().getName()));
return map.get(Thread.currentThread().getName());
}
}
static  class B{
public int get(){
System.out.println(Thread.currentThread().getName()+" has B get data: "+map.get(Thread.currentThread().getName()));
return map.get(Thread.currentThread().getName());
}
}
}


运行结果如下

Thread-0 has put data: -619140736
Thread-1 has put data: 1805075629
Thread-0 has A get data: -619140736
Thread-0 has B get data: -619140736
Thread-1 has A get data: 1805075629
Thread-1 has B get data: 1805075629


源码地址：https://github.com/haha174/thread-learning.git

文章地址：http://www.haha174.top/article/details/251787
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标签：  string 多线程 线程 并发 应用
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