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

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.