Chapter 18 Exercise 25, Introduction to Java Programming, Tenth Edition Y. Daniel LiangY.

18.25 (String permutation)
Write a recursive method to print all the permutations of a
string. For example, for the string abc, permutation is:
abc
acb
bac
bca
cab
cba

import java.util.Scanner;

public class Exercise_25 {

    public static void main(String[] args) {

        System.out.print("Enter a string: ");
        String s = new Scanner(System.in).next();
        System.out.println("All possible permutations of " + s + " are: ");

        displayPermutation(s);
    }

    public static void displayPermutation(String s) {
        displayPermutation("", s);
    }

    public static void displayPermutation(String s1, String s2) {

        if (s2.length() == 0) {
            System.out.println(s1);
        } else {
            for (int i = 0; i < s2.length(); i++) {
                displayPermutation(s1 + s2.charAt(i), s2.substring(0, i) + s2.substring(i + 1));
            }
        }
    }

}