java核心知识点学习----多线程间的数据共享和对象独立,ThreadLocal详解

            package
             com.amos.concurrent;

            import
             java.util.HashMap;

            import
             java.util.Map;

            import
             java.util.Random;

            /**
            
 * @ClassName: ThreadScopeShareData
 * @Description: 下面的例子用的是Map对象将数据实现共享
 * 
            @author
            : amosli
 * @email:hi_amos@outlook.com
 * @date Apr 20, 2014 6:19:02 PM
 
            */
            public
            class
             ThreadScopeShareData {

            
                public
                static Map<Object, Integer> map = new HashMap<Object, Integer>();
    
            public
            static
            void
             main(String[] args) {
        
            for (int i = 0; i < 3; i++) {
            new Thread(new Runnable() {
                publicvoid run() {
                    intdata = new Random().nextInt();//给data设值,
                    System.out.println(Thread.currentThread().getName() + " set data:" + data);
                    map.put(Thread.currentThread(), data);//将值按照Thread去设值,取的时候也按Thread去取,以保证数据的共享,但又保证了对象的独立.new A().get();
                    new B().get();
                }
            }).start();
        }
    }

    staticclass A {//这里A和B的方法虽然是一样的,这里是想表示有可能调用不同的对象去执行数据操作publicint get() {
            data = map.get(Thread.currentThread());
            System.out.println("a from thread:" + Thread.currentThread().getName() + " is " + data);
            return data;
        }
    }

    staticclass B {
        publicint get() {
            int data = map.get(Thread.currentThread());
            System.out.println("b from thread:" + Thread.currentThread().getName() + " is " + data);
            return data;
        }
    }

}

            public
            class
             ThreadLocalShareData {
    
            
                private
                static ThreadLocal<Integer> threadLocal = new ThreadLocal<Integer>();
    
            public
            static
            void
             main(String[] args) {
        
            for (int i = 0; i < 3; i++) {
            new Thread(new Runnable() {
                publicvoid run() {
                    int data = new Random().nextInt();//给data设值,
                    System.out.println(Thread.currentThread().getName() + " set data:" + data);
                    threadLocal.set(data);//使用ThreadLocal来设值new A().get();
                    new B().get();
                }
            }).start();
        }
    }
    staticclass A {//这里A和B的方法虽然是一样的,这里是想表示有可能调用不同的对象去执行数据操作publicint get() {
            int data = threadLocal.get();
            System.out.println("a from thread:" + Thread.currentThread().getName() + " is " + data);
            return data;
        }
    }
class B....
...
}

            public
            void
             set(T value) {
        Thread t = Thread.currentThread();
        ThreadLocalMap map = getMap(t);
        if (map != null)
            map.set(this, value);
        else
            createMap(t, value);
    }

            public
             T get() {
        Thread t = Thread.currentThread();
        ThreadLocalMap map = getMap(t);
        if (map != null) {
            ThreadLocalMap.Entry e = map.getEntry(this);
            if (e != null)
                return (T)e.value;
        }
        return setInitialValue();
    }

            package
             com.amos.concurrent;

            class
             Account {
    
            /*
            
     * 定义一个ThreadLocal类型的变量,该变量是一个线程局部变量
     
            */
            private ThreadLocal<String> name = new ThreadLocal<String>();

    // 定义一个初始化name属性的构造器public Account(String str) {
        this.name.set(str);
        // 下面的代码用于访问当前线程的name副本的值
        System.out.println("------" + this.name.get());
    }
    // name的getter,setter方法public String getName() {
        return name.get();
    }
    publicvoid setName(String str) {
        this.name.set(str);
    }
}

class MyTest extends Thread {
    // 定义一个Account属性private Account account;

    public MyTest(Account account, String name) {
        super(name);// 设置thread的名称this.account = account;
    }

    @Override
    publicvoid run() {
        // 循环for (int i = 0; i < 10; i++) {
            if (i == 6) {// 当i=6时,将name名称更改为当前的线程名                account.setName(getName());
            }
            System.out.println(account.getName() + " 账户i的值:" + i);
        }
    }
}
publicclass ThreadLocalTest {
    publicstaticvoid main(String[] args) {
        Account account = new Account("初始名称");
        // 启动两个线程,两人个线程共享同一个账户,即只有一个账户名./*
         * 虽然丙个线程共享同一个账户,即只有一个账户名.但由于账户名是ThradLocal类型的,所以每个线程都完全拥有各自的账户名副本,
         * 因此在ｉ=６以后,将看到两人个线程访问同一个账户时出现不同的账户名
         */new MyTest(account, "张三").start();
        new MyTest(account, "李四").start();
    }
}