Analysis of the reasons why $ should not be used in Java classes

The following is the definition of identifiers in Java

In most people’s understanding, Java identifiers The definition rules are as follows.

1. The identifier consists of letters, numbers, currency symbols (￥, $, etc.), and connection symbols (_, etc.). (The letters here are Unicode character sets, and are no longer limited to the traditional 26 English letters.)

2. The first character of the identifier can be a letter, currency symbol, or connection symbol, but it cannot be a number.

3. The identifier cannot be the same as the keyword in Java.

4. The identifier cannot be the same as the predefined literal constant name in Java (true, false, null).

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But sometimes when you use $ easily, you will have unexpected surprises. For example, the following code:

Creates an inner class xy ​​in Ly's class

Then what? When running this class, something surprising happened after compilation. Two class files, Lyxy.class and Ly.class, were generated. If we were writing two class files, Ly xy.class and Ly.class, if we were writing Write two class files, Lyxy.class and Ly.class. If we are writing a Lyxy, will there be duplication of classes?

If you write according to the following method, there will be duplication of classes

What exactly Which category is repeated? You can refer to the above running results for analysis.

From the class file generated by the above running, it can be seen that Ly$xy.class will be repeated, so an error will be reported.

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