Question

I am a beginner in Java and am doing an exercise from a book. The task is to write a static method which takes as an argument a string array and returns a jumbled up version of the string in random order. To create a random number you must use the following:

import java.util.Random;
Random r = new Random();
int rand = r.nextInt();

My answer is as follows:

private static String[] jumble(String[] arr){
    String [] jumbled = new String[arr.length];
    int [] chosen = new int [arr.length];
    Random r = new Random();
    int rand = r.nextInt(arr.length);
    chosen[0] = rand;
    jumbled[0] = arr[rand];
    for(int i = 1; i < arr.length; i++){
        while(checkIfChosen(chosen, rand, i)){
            rand = r.nextInt(arr.length);
        }
        chosen[i] = rand;
        jumbled[i] = arr[rand];
    }
    print(jumbled);
    return jumbled;
}


private static void print(String[]arr){
    for(int i = 0; i < arr.length; i++){
        System.out.println(arr[i]);
    }
}

private static boolean checkIfChosen(int[] arr, int a, int ind){
    for(int i = 0; i < ind; i++){
        if(arr[i]==a){
            return true;
        }
    }
    return false;
}

This does work but it seems so bl**dy long winded for something so simple. Can anyone improve on this? Any easier ways to implement such a task adhering to the constraints mentioned in the question?

EDIT: With Fisher Yates Shuffle:

public static void main(String[] args) {
    String [] original = {"Hello", "How", "Are", "You"};
    jumble(original);
}


private static String[] jumble(String[] arr){
    Random r = new Random();
    for(int i = arr.length-1; i > 0; i--){
        int rand = r.nextInt(i);
        String temp = arr[i];
        arr[i] = arr[rand];
        arr[rand] = temp;
    }
    print(arr);
    return arr;
}


private static void print(String[]arr){
    for(int i = 0; i < arr.length; i++){
        System.out.println(arr[i]);
    }
}

A great piece of code and much more efficient than my answer. Thanks.

Answer 1

You probably just want to use the Fisher-Yates shuffle for this. It only takes one pass to do it and should produce a “fair” shuffle (assuming your random number generator has enough bits of entropy).