多线程之ThreadLocal类

ThreadLocal

变量值的共享可以使用public static变量形式,类ThreadLocal主要解决的就是每个线程绑定自己的值。

隔离性

类ThreadLocal解决的是变量在不同线程间的隔离性，也就是不同线程拥有自己的值，不同线程中的值是可以放入ThreadLocal类进行保存的

Java例子

public class Tool {
    public static ThreadLocal threadLocal=new ThreadLocal();

}


public class ThreadA extends Thread{
    @Override
    public void run() {
        for (int i = 0; i <5 ; i++) {
            Tool.threadLocal.set(i);
            System.out.println("ThreadA get Value=" + Tool.threadLocal.get());
            try {
                Thread.sleep(3000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

public class ThreadB extends Thread {
    @Override
    public void run() {
        for (int i = 0; i <5 ; i++) {
            Tool.threadLocal.set(i);
            System.out.println("ThreadB get Value=" + Tool.threadLocal.get());
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}


public class Run {
    public static void main(String[] args) {
        ThreadA threadA=new ThreadA();
        threadA.start();
        ThreadB theadB =new ThreadB();
        theadB.start();
        for (int i = 0; i <5 ; i++) {
            Tool.threadLocal.set(i);
            System.out.println("MainThread get Value=" + Tool.threadLocal.get());
            try {
                Thread.sleep(2000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

    }
}

结果：

ThreadA get Value=0
ThreadB get Value=0
MainThread get Value=0
ThreadB get Value=1
MainThread get Value=1
ThreadB get Value=2
ThreadA get Value=1
ThreadB get Value=3
MainThread get Value=2
ThreadB get Value=4
MainThread get Value=3
ThreadA get Value=2
MainThread get Value=4
ThreadA get Value=3
ThreadA get Value=4

initialValue方法设置初始值

类ThreadLocal 可以在main线程和其他线程里设置初始值

Java例子:

public class Tools {
    public static ThreadLocal tools=new ThreadLocalExt();
}


public class ThreadLocalExt extends ThreadLocal {
    @Override
    protected Object initialValue() {
        return new Date().getTime();
    }
}

public class ThreadC extends Thread{
    @Override
    public void run() {
        for (int i = 0; i <5 ; i++) {
            System.out.println("ThreadC线程中取值="+Tools.tools.get());
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

public class Test {
    public static void main(String[] args) throws InterruptedException {
        ThreadC threadC=new ThreadC();
        threadC.start();
        for (int i = 0; i <10 ; i++) {
            System.out.println("在Mian线程中取值="+Tools.tools.get());
            Thread.sleep(2000);
        }
    }
}

结果:

ThreadC线程中取值=1545141944675
在Mian线程中取值=1545141944675
ThreadC线程中取值=1545141944675
在Mian线程中取值=1545141944675
ThreadC线程中取值=1545141944675
ThreadC线程中取值=1545141944675
在Mian线程中取值=1545141944675
ThreadC线程中取值=1545141944675
在Mian线程中取值=1545141944675
在Mian线程中取值=1545141944675
在Mian线程中取值=1545141944675
在Mian线程中取值=1545141944675
在Mian线程中取值=1545141944675
在Mian线程中取值=1545141944675
在Mian线程中取值=1545141944675