Write a program that find all possible combination of picking 3 letters or numbers

1. write a statement that declares a string variable named city. the variable should be initialized so it references an object with the string “san francisco”. a) assume that stringlength is an int variable. write a statement that stores the length of the string referenced by the city variable (declared in question1) in stringlength. b) assume that onechar is a char variable. write a statement that stores the first char- acter in the string referenced by the city variable (declared in question1) in onechar. c) assume that uppercity is a string reference variable. write a statement that stores the uppercase equivalent of the string referenced by the city variable (declared in question 1) in uppercity. d) assume that lowercity is a string reference variable. write a statement that stores the lowercase equivalent of the string referenced by the city variable (declared in question 1) in lowercity.