单线程执行设计模式

• 有一个门，始终只能有一个人通过（实际上这里的门就是指共享资源）

• Gate

public class Gate {
    private int counter = 0;
    private String name = "Nobody";
    private String address = "Nowhere";

    /**
     * 临界值
     *
     * @param name
     * @param address
     */
    public synchronized void pass(String name, String address) {
        this.counter++;
        /*race*/
        this.name = name;
        this.address = address;
        verify();
    }

    private void verify() {
        if (this.name.charAt(0) != this.address.charAt(0)) {
            System.out.println("*******BROKEN********" + toString());
        }
    }

    public synchronized String toString() {
        return "No." + counter + ":" + name + "," + address;
    }
}

• user

public class User extends Thread {

    private final String myName;

    private final String myAddress;

    private final Gate gate;

    public User(String myName, String myAddress, Gate gate) {
        this.myName = myName;
        this.myAddress = myAddress;
        this.gate = gate;
    }

    @Override
    public void run() {
        System.out.println(myName + " BEGIN");
        while (true) {
            this.gate.pass(myName, myAddress);
        }
    }
}

• client

public class Client {
    public static void main(String[] args) {
        Gate gate = new Gate();
        User bj = new User("Baobao", "Beijing", gate);
        User sh = new User("ShangLao", "ShangHai", gate);
        User gz = new User("GuangLao", "GuangZhou", gate);

        bj.start();
        sh.start();
        gz.start();
    }
}