(String permutation) Write a recursive method to print all the permutations of a string. For example, for the string abc, the permuation is

(String permutation) Write a recursive method to print all the permutations of a string. For example, for the string abc, the permuation is

abc

acb

bac

bca

cab

cba

(Hint: Define the following two methods. The second is a helper method.)

public static void displayPermutation(String s)

public static void displayPermutation(String s1, String s2)

The first method simply invokes displayPermutation(" ", s). The second method uses a loop to move a character from s2 to s1 and recursively invokes it with a new s1 and s2. The base case is that s2 is empty and prints s1 to the console. Write a test program that prompts the user to enter a string and displays all its permutations.