How do I generate random numbers for that array that don't repeat? (java)

Question

So I'm trying to make a sports game schedule generator. This randomly selects from an array that consists of field names. How do I make it so that It won't select the same field twice?

    Random rand = new Random();
    int index, loc;
    index = rand.nextInt();
    loc = rand.nextInt(y);
    System.out.print(fields[loc]);

Answer 1

Create a seperate array of the same size as your fields array of boolean type, then when a location is selected:

loc = rand.nextInt(y);
alreadySelected[loc] = true;
if(!alreadySelected[loc]) {
    System.out.print(fields[loc]);
}

This will make it so that if you've already been at that location, it won't print it out again.

Answer 2

public static void main(String[] args) {
    ArrayList<> list = new ArrayList<Integer>();
    for (int i = 0; i < 1000; i++) {
        list.add(new Integer(i));
    }
    Collections.shuffle(list);
    System.out.println(list.get(0));

}

Add each number in the range sequentially in a list structure using add() method of List Interface.Then use shuffle of Collections class to shuffle the list

Collections.shuffle() generate random number from a given list using default source of randomness.

Answer 3

You should store the indexes of sports in another integer from where we can check that this sport has not been chosen earlier. first store the indexes of sports in a string.

public void sportPicker(){
    int[] sche=new int[4];
    String[] sports={"1-Cricket","2-Hockey","3-Tennis","4-Badminton"}
    int temp;
    Random rand=new Random();
    for(int a=1;a<=sports.length();a++){
        temp=rand.nextInt(4);
        if(temp!=sche[0]||temp!=sche[1]||temp!=sche[2]||temp!=sche[3]){
            sche[a]=temp;
        }
        else a--;
    }
}

This would make sure that index is not there in the array sche, if it exists it would make the fuction again generate a number and check.