[JAVA] Summary of jar files

I am a beginner in programming. This time, I got an overview of the jar file, so I will output it.

Q1: What is the jar file made up of?

I felt that it was necessary to know the following three words in order to know it.

① ** Class library **: Convenient functions that can be used in development such as System.out.println and Random (There are many other functions) ② ** Class **: A box for collecting class libraries ③ ** Package **: Box for grouping classes

`Q: Why do I have to package the classes together? ʻA: To distinguish between classes that have the same name in the code.

For example, "** java.sql . Date" and " java.util **. Date" are expressed as "Date" in the source. In both cases, the class name is "Date", but they can be distinguished by the package name. (Package name in bold) *

Summary,,,,,,

Contents of the class	Package contents	Contents of the jar file
Class library	class	package

It is like that. A jar file is a compressed package in jar format.

** If you want to know more about jar format, please refer to the URL below ** https://wa3.i-3-i.info/word14171.html

I'm sorry if there is a wrong place, but I would appreciate it if you could teach from the comments. *

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