Can you explain to me how the permuteString method works it is so confusing.

import java.util.Scanner;

public class Permutations { // FIXME: Use a static variable to count permutations. Why must it be static?

public static void permuteString(String head, String tail) { char current; String newPermute; int len; int i;

current = '?'; len = tail.length();

if (len <= 1) { System.out.println(head + tail); } else { for (i = 0; i < len; ++i) { current = tail.charAt(i); // Get next leading character newPermute = tail.substring(0, i) + tail.substring(i + 1); // Get the rest of the tail permuteString(head + current, newPermute); } } }

public static void main(String [] args) { final String PROMPT_STRING = "Enter a string to permute ( to exit): "; Scanner scnr = new Scanner(System.in); String input;

// Get input and permute the string System.out.println(PROMPT_STRING); input = scnr.nextLine();

permuteString("", input);

System.out.println("Done."); } }

// Input = abc