/** 线程安全，但效率低 懒汉，线程安全
private static ImAddressPool instance = null;
private ImAddressPool() {}
public synchronized static ImAddressPool getInstance() {
if (instance == null) {
instance = new ImAddressPool();
instance.init();
}
return instance;
}
**/
// 类装载时就实例化 饿汉
/***
private static ImAddressPool instance = new ImAddressPool();
private ImAddressPool() {
init();
}
public static ImAddressPool getInstance() {
return instance;
}
**/
// 内部静态类方式
private static class SingletonHolder {
private static final ImAddressPool INSTANCE = new ImAddressPool();
}
private ImAddressPool (){
init();
}
public static final ImAddressPool getInstance() {
return SingletonHolder.INSTANCE;
}