Please write the code in java  

(Recursion):

Implement a SubsetGenerator that generates all subsets of the characters of a string. For example, the subsets of the characters of the string “rum” are the eight strings

“rum”,  “ru”,  “rm”,  “r”,  “um”,  “u”,  “m”,  “ ”

Note that the subsets don’t have to be substrings – for example, “rm” isn’t a sub-string of “rum”.

(Sorting and Searching):

Write a program that selection sort algorithm to sort an array of integers in descending order.

(Sorting and Searching):

Sort an array list of strings by increasing length, Hint: Supply a Comparator.