What is the static constant in the class file?

Recently wrote a project encountered a problem, back and forth a few times, finally explored clearly. No nonsense, on the example.

Background: Because the project is small and the configuration file is not used, all static constants are placed inside the Config.java.

public class Config {public    static final String url= "http://www.xxxx.com/";    public static final int page_num=10;}

It looks good too, no big problem, it's all used.

Well, put it on the server and run it, normal.

Next, the question comes.

URL change, Page_num also changed.

public class Config {public    static final String url= "http://www.yyyy.com/";    public static final int page_num=200;}

OK, generate the next class file, put it on the server, have a cup of tea ...

Refresh under, unchanged, and so on, the server has a conversion time ...

30s ... Hasn't changed.

1min ... Hasn't changed.

Restart the server ... (It should be OK)

Why still not change [email protected]@@###&&&+++*** (What's going on, the server is broken, re-installed?) ）

In fact, nothing is bad. You don't believe me? Look down.

Find a gadget, decompile the class file, and look for a reference constant, and you'll see for a moment.

It's not what you think.

Config.URLConfig.PAGE_NUM

But

"http://www.xxxx.com/" 10

See, constants are replaced with values directly in the class file.

That still want to use Config.java, do not want to change many places, how to do?

Two methods:

public class Config {public    static final string Url=new string ("http://www.xxxx.com/");//Useful public    static final int page_num=new Integer (10);//Bad use}

public class Config {public    static String GetURL () {return ' http://www.yyyy.com ';    }     public static int Getpagenum () {return;    }}

Well, the rest, waiting for everyone to find out.

What is the static constant in the class file?