permutations_of_string.java

import java.util.*;

public class Perm {
	
	public static ArrayList<String> getPerms(String str)
	{
		if (str==null) 
			return null;
		ArrayList<String>  permutations = new ArrayList<String>();
		if(str.length() ==0){permutations.add("");  return permutations;}
		char first = str.charAt(0);
		String remainder = str.substring(1);
		ArrayList<String>  words = getPerms(remainder);
		System.out.println(words);
		for(String word : words)
		{
			for(int j=0;j<=word.length();j++){
				String s = insertCharAt(word,first,j);
				permutations.add(s);
			}
		}
		System.out.println(permutations);
		return permutations;
	}
	
	public static String insertCharAt(String word, char c ,int i)
	{
		String start = word.substring(0,i);
		String end= word.substring(i);
		return start+c+end;
	}
	public static void main(String args[])
	{
		Scanner sc = new Scanner(System.in);
		String s = sc.nextLine();
		ArrayList<String> o = getPerms(s);
		System.out.println(o);
		
	}
}