How to write java program in intellij idea?

As shown in the figure:

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1, Java code compilation is done by the Java source code compiler, the flowchart is shown below: ?

Java code compilation

2, Java byte code (class file) execution is done by the JVM execution engine, the flow chart is shown below:?

Java bytecode execution

3, Java code compilation and execution of the entire process contains the following three important mechanisms:?

Java source code compilation mechanism

Class loading mechanism

Class execution mechanism

4, Java source code compilation consists of the following three processes:?

Analysis and input to the symbol table?

Annotation processing?

Semantic analysis and generation of class files?

The flowchart is shown below:

5. The final generated class file consists of the following parts:?

Structural information: including the class file format version number and the number and size of each part of the information .

Metadata: corresponds to the Java source code declaration and constant information. Includes class/inherited superclass/implemented interface declarations, domain and method declarations, and constant pools.

Method information: corresponds to the information corresponding to statements and expressions in Java source code. Includes bytecode, exception handler table, evaluated

and local variable area size, evaluated stack type record, debugging symbols information.