safe publication

SafePub.java

package chap06;

import java.util.concurrent.TimeUnit;

/**
 * Created by wang.bh
 */
class Bag {
    private final String item; // <-- no final here

    public String getItem() {
        return item;
    }

    public Bag(String item) {
        this.item = item;
    }
}

class ThreadB extends Thread {
    private Bag bag;

    public /*synchronized*/ void grab(Bag bag) {
        this.bag = bag;
    }

    @Override
    public void run() {
        try {
            while (true) {
                //synchronized (this) {
                    if (bag != null) {
                        TimeUnit.MILLISECONDS.sleep(500);
                        System.out.println(bag.getItem());
                    }
                //}
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

public class SafePub {
    public static void main(String args[]) throws InterruptedException {
        ThreadB t = new ThreadB();
        t.start();
        TimeUnit.SECONDS.sleep(1);
        Bag bag = new Bag("HI");
        t.grab(bag);
    }
}