Class loading and classloader understanding

1、 load ： Class like class Bytecode file loaded into memory , And convert the static data into the method area （ Special piles ） The runtime data structure of . At this stage , Generate... Representing this class java.lang.Class object .

2、 link ： take Java Class to JRE in

• verification ： Ensure that the loaded class information complies with JVM standard , There are no security issues ;
• Get ready ： Officially a class variable （static） Allocate memory , And set the default initial value of class variables , This memory is allocated in the method area ;
• analysis ： take JVM Symbol references in constant pools （ Constant names ） Replace with direct reference （ Address ）.

3、 initialization ：

• Execute the static（ Static code block 、 Static variables ） A combined class constructor ().（ The class constructor here is used to construct class information classes , No Constructor for constructing class objects ）
• When initializing a class , It is found that his parent class has not been initialized , Then we will initialize its parent class first .
• JVM Ensure that a class () Methods are locked and synchronized correctly in a multithreaded environment .

（ Focus on the bold part ）