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);
}
}
}