Java equivalent for this python code

Question

I was messing around in python and I found this library called itertools. It is very useful for challenges you'd come across at at a competition. However only one of three competitions I go to accepts python. They all support mainly java and other various c style languages.

Anyways I wrote this code in python and want to translate it into java.

import itertools
array = [''.join(x) for x in itertools.permutations(input("Enter a word: "))] 
print(",".join(array).replace(",", "\n")) 

This will print out all permutations of a word that are length of the word.

Examples: hi ---> hi, ih

foo---> foo, foo, ofo, oof, ofo, oof

(Yes there are duplicates disregard them when answering)

Now I am aware of this java code that is similar to what I've made (Don't bother examining it. Just know it does the same task)

public class Permutations {
    // print N! permutation of the characters of the string s (in order)
    public  static void perm1(String s) { perm1("", s); }
    private static void perm1(String prefix, String s) {
        int N = s.length();
        if (N == 0) System.out.println(prefix);
        else {
            for (int i = 0; i < N; i++)
               perm1(prefix + s.charAt(i), s.substring(0, i) + s.substring(i+1, N));
        }

    }

    // print N! permutation of the elements of array a (not in order)
    public static void perm2(String s) {
       int N = s.length();
       char[] a = new char[N];
       for (int i = 0; i < N; i++)
           a[i] = s.charAt(i);
       perm2(a, N);
    }

    private static void perm2(char[] a, int n) {
        if (n == 1) {
            System.out.println(a);
            return;
        }
        for (int i = 0; i < n; i++) {
            swap(a, i, n-1);
            perm2(a, n-1);
            swap(a, i, n-1);
        }
    }  

    // swap the characters at indices i and j
    private static void swap(char[] a, int i, int j) {
        char c;
        c = a[i]; a[i] = a[j]; a[j] = c;
    }



    public static void main(String[] args) {
       int N = Integer.parseInt(args[0]);
       String alphabet = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
       String elements = alphabet.substring(0, N);
       perm1(elements);
       System.out.println();
       perm2(elements);
    }
}

Now in the crunch time of a competition I'd really prefer to use my 3 lined code opposed to this but, I can't because of the restrictions. Is anyone aware of a library in java that is similar to python's itertools?

Answer 1

Guava's Collections2.permutations might do the job, but as many other people have said, third-party libraries usually aren't fair game for contest programming. (There's nothing for this built into Java.)