Java design pattern-Singleton mode

Previously all only knew the code, sometimes encountered such a problem, in a class want to invoke another class inside the method, or member variables, each time to new, or to set the class member to static, but it is inconvenient, and sometimes that class every time new, The inside constructor adds new data, and so on. In the absence of this singleton pattern, I used a static member to save an instance of that class, and each time new was judged whether it was new or not, but it was not suitable for expansion. Then we found the singleton pattern:

This is the first simplest pattern I have touched in several modes. Look at the code:

Public single{public  static single single=null;    public static single getinstance () {if (single==null) single=new single (), return single;}

The above is all, the use of time outside do not judge. Direct:

Single.getinstance (). Xxxx

Can call the inside of the thing, is not very convenient