设计模式 之 单例模式简单例子(Java)

package com.stephen.javatest02;

public class MachineConfig {
private static MachineConfig a = null;
private String ServerIP="";
private int ServerPort=0;

private MachineConfig()
{
}

public String getServerIp()
{
return this.ServerIP;
}

public int getServerPort()
{
return this.ServerPort;
}

public synchronized void setServerParam(String ServerIP, int ServerPort)
{
this.ServerIP = ServerIP;
this.ServerPort = ServerPort;
}

public static synchronized MachineConfig getInstance()
{
if(null == a)
a = new MachineConfig();
return a;
}
}

调用方法：
MachineConfig mc = MachineConfig.getInstance();
mc.setServerParam("172.16.24.19", 8080);
System.out.println("server ip:" + mc.getServerIp());
System.out.println("server port:" + mc.getServerPort());

MachineConfig mc2 = MachineConfig.getInstance();
mc2.setServerParam("192.168.1.1", 6981);
System.out.println("server ip:" + mc.getServerIp());
System.out.println("server port:" + mc.getServerPort());

运行结果：
server ip:172.16.24.19
server port:8080
server ip:192.168.1.1
server port:6981