Java中ThreadLocal模拟和解释 (一)

一、测试代码

public class XY_ThreadData
{
private static Integer data = 0;
private static Map map = new HashMap();
private static ThreadLocal local = new ThreadLocal();

public static void setData(Integer value)
{
data = value;
}

public static Integer getData()
{
System.out.println("ThreadName：" + Thread.currentThread() + " data value：" + data);
return data;
}

public static void setMapData(Integer value)
{
map.put(Thread.currentThread(), value);
}

public static Integer getMapData()
{
Object obj = map.get(Thread.currentThread());
System.out.println("ThreadName：" + Thread.currentThread() + "map value：" + obj);
return Integer.parseInt(obj.toString());
}

public static void setThreadLocalData(Integer value)
{
local.set(value);
}

public static Integer getThreadLocalData()
{
Object obj = local.get();
System.out.println("ThreadName：" + Thread.currentThread() + "threadlocal value：" + obj);
return Integer.parseInt(obj.toString());
}
}

public class XY_ThreadData_Test
{
public static void main(String[] args)
{
for (int i = 0; i < 10; i++)
{
new Thread(new Runnable() {
public void run()
{
final int value = new Random().nextInt(); // 每个线程自己创建的变量
XY_ThreadData.setData(value);
XY_ThreadData.getData();
}
}).start();
}

}
}
ThreadName：Thread[Thread-3,5,main] data value：1046062244
ThreadName：Thread[Thread-6,5,main] data value：-879673875
ThreadName：Thread[Thread-2,5,main] data value：-125397465
ThreadName：Thread[Thread-4,5,main] data value：-1546413071
ThreadName：Thread[Thread-0,5,main] data value：754770101
ThreadName：Thread[Thread-8,5,main] data value：-1666786926
ThreadName：Thread[Thread-5,5,main] data value：-1666786926
ThreadName：Thread[Thread-9,5,main] data value：1046062244
ThreadName：Thread[Thread-1,5,main] data value：269410746
ThreadName：Thread[Thread-7,5,main] data value：269410746
分析：可以看到以下两个线程中data的值时一样的，没有做到各个线程变量独一份
ThreadName：Thread[Thread-8,5,main] data value：-1666786926
ThreadName：Thread[Thread-5,5,main] data value：-1666786926

public class XY_ThreadData_Test
{
public static void main(String[] args)
{
for (int i = 0; i < 10; i++)
{
new Thread(new Runnable() {
public void run()
{
final int value = new Random().nextInt();
XY_ThreadData.setMapData(value);
XY_ThreadData.getMapData();
}
}).start();
}

}
}
ThreadName：Thread[Thread-0,5,main]map value：-1138167111
ThreadName：Thread[Thread-4,5,main]map value：-1545929782
ThreadName：Thread[Thread-6,5,main]map value：-1612385717
ThreadName：Thread[Thread-3,5,main]map value：-1390594683
ThreadName：Thread[Thread-8,5,main]map value：518506934
ThreadName：Thread[Thread-2,5,main]map value：1583239372
ThreadName：Thread[Thread-5,5,main]map value：995578601
ThreadName：Thread[Thread-1,5,main]map value：-916627474
ThreadName：Thread[Thread-7,5,main]map value：-960206804
ThreadName：Thread[Thread-9,5,main]map value：-1187504747
分析：模拟线程变量独一份，无重复

public class XY_ThreadData_Test
{
public static void main(String[] args)
{
for (int i = 0; i < 10; i++)
{
new Thread(new Runnable() {
public void run()
{
final int value = new Random().nextInt();
XY_ThreadData.setThreadLocalData(value);
XY_ThreadData.getThreadLocalData();
}
}).start();
}

}
}
ThreadName：Thread[Thread-1,5,main]threadlocal value：935024745
ThreadName：Thread[Thread-4,5,ma