Let's sort out the "~~~ cases" used during programming.
When connecting multiple words, the rule is to write the first letter in lowercase and the second and subsequent words in uppercase.
hello world -> helloWorld programing language -> programingLanguage osaka city -> osakaCity
-Java method names and variable names
When connecting multiple words, the rule is to connect the words with "_ (underscore)".
hello world -> hello_world programing language -> programing_language osaka city -> osaka_city
-Relational database table names and column names
The rule is to capitalize the first letter of a word when connecting multiple words.
hello world -> HelloWorld programing language -> ProgramingLanguage osaka city -> OsakaCity
-Java object (class) name