Why String.indexOf function in Java take a int parameter to represent a char? [duplicate]

I am new to Java programing, and I am confused when using the String.IndexOf(int ch) in my code.

For example, I want to find the first occurrence of '-' in a string "abc-def-ghi".

so here is my code:

String test = "abc-def-ghi";
int firstOcc = test.IndexOf('-');

This code is working fine.

However, my question is, why String.IndexOf() function takes a int parameter as a char?

Is there any benefit to writing code as IndexOf(int ch) instead of IndexOf(char ch)?

Thanks for any help!