线程之旅--Single Threaded Execution Pattern

假设有这样一个环境，有个门，门的宽度恰好只能容许一个人经过，若又2个人同时进门，那么门的宽度将不符合

Single Threaded Execution Pattern  指的是一个线程执行的场所，就像上面所说的独木桥一样，这个模式用来限制同时只能让一个线程运行。加入synchronized修饰符修饰的方法，就只能让这个方法同一时刻只有一个线程能访问，大家可以试试，把Gate类的相关的方法的synchronized修饰符去掉了，会是什么效果

下面我们用个简单的例子来进行说明（范例由3个文件组成）：

--------------------Main.java --主程序调用-并让3个人不断的进出门

public class Main {
    public static void main(String[] args) {
        System.out.println("开始, 按 CTRL+C to exit.");
        Gate gate = new Gate();
        new UserThread(gate, "湖北人", "湖北").start();
        new UserThread(gate, "广州人", "广州").start();
        new UserThread(gate, "浙江人", "浙江").start();
    }
}

------------------Gate.java --当人进出时，会记录人的姓名和籍贯

public class Gate {
    private int counter = 0;
    private String name = "Nobody";
    private String address = "Nowhere";
    public synchronized void pass(String name, String address) {
        this.counter++;
        this.name = name;
        this.address = address;
        check();
    }
    public synchronized String toString() {
        return "No." + counter + ": " + name + ", " + address;
    }
    private void check() {
        if (name.charAt(0) != address.charAt(0)) {
            System.out.println("***** BROKEN ***** " + toString());
        }
    }
}

}

--------------------UserThread--人的类，负责不断的在门间穿梭

public class UserThread extends Thread {
    private final Gate gate;
    private final String myname;
    private final String myaddress;
    public UserThread(Gate gate, String myname, String myaddress) {
        this.gate = gate;
        this.myname = myname;
        this.myaddress = myaddress;
    }
    public void run() {
        System.out.println(myname + " BEGIN");
        while (true) {
            gate.pass(myname, myaddress);
        }
    }
}