方法积累系列二

//单例模式一

public class SingletonIn {

private static SingletonIn instance = null;
public static SingletonIn getInstance(){
if(instance == null){
instance = new SingletonIn();
}
return instance;
}
}

//单例模式二

public class SingletonOut {
private static SingletonOut instance = new SingletonOut();
public static SingletonOut getInstance(){
return instance;
}
}