Permutations of integer

Hi,

I need some help with a task I'm working on I feel very stuck. I have sent the file to work on andtechtest_external.zip.

This is the brief:

"Two non-negative integers are called AND-Siblings if they can be obtained by each other by rearranging the digits of their decimal representations.
Write the function:
public static String solution(String input) throws NumberFormatException {
return null;}

So that, given any String input, returns all the distinct AND-Siblings that can be formed by the positive integers that can be found on it in descending order. Please keep in mind the efficiency of your algorithm when writing the solution.

To be included.
● If the input provided is: “236”, then your solution should return “632,623,362,326,263,236" as these are all the combination that can be made with integers that the string contains.

● If the input provided is: “A 3B2 C6D”, then your solution should return "632,623,362,326,263,236" as well, but this time notice that the provided string had
non-integers characters and whitespaces, so an extraction of integers was first made to
obtain the correct solution.

● If the input provided does not contain any integers: “ABC”, then your solution should
return the appropriate error exception message.

● Keep things simple, don’t over-engineer your solution."

Thanks. Please include documentation.