Does String contain case-sensitive?

No, Java is case sensitive so it is possible to have two separate methods like foo(String s) and Foo(String s) in the same class.

contains() method in Java? The contains() method in Java is used to search the substring in a given String . Returns: If the substring is found in the specified String, then it returns a true value; otherwise, it returns​ a false value.

Yes, contains is case sensitive . You can use java.17 Eyl 2008

The string. Contains() method in C# is case sensitive . And there is not StringComparison parameter available similar to Equals() method, which helps to compare case insensitive.