in the simplest way possible please, a Java task

i want a new solution, not the one already posted before

Presentation exercise 1 Write a method that, given two Strings, checks whether one is a permutation of the other. You can assume that the two strings only contain letters of the English alphabet. Your method should not be case sensitive. If n is the number of characters in the strings, can you write a method that performs this task using a number of steps which can be represented by the function c*n+C2, where both e, and ca are constants? (i.e. can you write a method that runs in O(n) ?)