random suffling java

import java.util.Random;

Random rand = new Random();

// Obtain a number between [0 - 49].
int n = rand.nextInt(50);

// Add 1 to the result to get a number from the required range
// (i.e., [1 - 50]).
n += 1;

void shuffle(int [] arr) {
        for (int i = 0; i < arr.length; i++) {
            int index = (int) (Math.random() * arr.length);
            int temp = arr[i];
            arr[i] = arr[index];
            arr[index] = temp;
        }
    }

for (int i = myList.length - 1; i > 0; i--){
            int j = (int) (Math.random() * (i + 1));

            double temp = myList[i];
            myList[i] = myList[j];
            myList[j] = temp;
        }