Java Regular Expression with Either Uppercase or Lowercase, but not both

Question

I am working on an expression for a password, where the validation should contain

1. must contains letters with numbers or symbols( NOT letters, numbers and symbols)
2. Uppercase or Lowercase( NOT a combination of both)
3. Min length of password is 8

based on the inputs provided by Mena, i have updated my expression to

String patternChar = "^[a-z&&[^A-Z]]+|[A-Z&&[^a-z]]+$";
String patternNumber = "^[a-zA-Z0-9&&[\\S]]+|[a-zA-Z\\S&&[^0-9]]+$";

1. PatternChar works fine for only Upper or Lower Case.
2. PatternNumber does work if i combine PatternChar with numbers or symbols.

here symbol means all UTF8 or unicode characters like e.g. £$%^

Thanks for your help.

but has problems.

Regards Ram