What are the naming rules for Java variables?

The naming rules for Java variables are as follows:

1. Variable names can only be composed of letters, numbers, and underscores.
2. The first character of a variable name must be a letter or underscore.
3. Variable names cannot be Java keywords (such as int, String, public, etc.).
4. Variable names are case-sensitive, meaning that the uppercase and lowercase letters in the variable name are distinct.
5. Variable names should be descriptive in order to clearly express the purpose of the variable.
6. Variables should be named using the camelCase naming convention, where the first word is lowercase and subsequent words are capitalized (e.g. myVariableName).
7. Avoid using abbreviations or acronyms as much as possible to ensure the readability and understanding of variable names.