String object (constant) pool

The main purpose of object pool is to realize data sharing and processing , With String Object pool as an example , The content is for reuse , Reuse actually belongs to shared design . But in java Middle target （ Constant ） There are two types of pools .

• Static constant pool ： In procedure （*.class） When loading, the string saved in this program will be automatically 、 Ordinary constants 、 Class and method information, etc , Allocate all

  String strA="www.baidu.com";
  String strB="www"+"baidu"+"com";
  System.out.println(strA==strB);//true
  

  Everything in this program is constant data （ String constants are all anonymous data ）, Therefore, the corresponding connection will be handled when the program is loaded ;

• Runtime constant pool ： After a program is loaded , There may be some variables in it

  String info="baidu";
  String strA="www.baidu.com";
  String strB="www"+info+"com";// Stored in the runtime constant pool 
  System.out.println(strA==strB);//false
  

  This is because info It's a variable. , The contents of variables can be modified , The program is not sure when it is loaded info What is it . So when you connect strings , I don't think StrB The structure of is the desired end result .