Create a method "addNumberEnd(String password)" in java?

I would like to create a array method "addNumberEnd(String password)" that returns and stores a string that has an added number(0-9) at the end of the string. For example, I have a string "mike" and I want it to return "mike0", "mike1" until "mike9". So, if I want to retrieve array[2], I would retrieve "mike2".