How do I randomize an array without any repeating/duplicate strings?

Question

I can randomize my strings that I set to each button in android but there are duplicates of the same letters. How do I do it without any duplicate letters?

    Random random = new Random();
    String[] letters = {"G","O","K","U","H","A","N","L","Z","M"};

    c1r1 = (Button) findViewById(R.id.btn1);
    c2r1 = (Button) findViewById(R.id.btn2);
    c3r1 = (Button) findViewById(R.id.btn3);
    c4r1 = (Button) findViewById(R.id.btn4);
    c5r1 = (Button) findViewById(R.id.btn5);
    c1r2 = (Button) findViewById(R.id.btn6);
    c2r2 = (Button) findViewById(R.id.btn7);
    c3r2 = (Button) findViewById(R.id.btn8);
    c4r2 = (Button) findViewById(R.id.btn9);
    c5r2 = (Button) findViewById(R.id.btn10);
    first = (Button) findViewById(R.id.first);
    second = (Button) findViewById(R.id.second);
    third = (Button) findViewById(R.id.third);
    fourth = (Button) findViewById(R.id.fourth);

    c1r1.setText("" + letters[random.nextInt(letters.length)]);
    c2r1.setText("" + letters[random.nextInt(letters.length)]);
    c3r1.setText("" + letters[random.nextInt(letters.length)]);
    c4r1.setText("" + letters[random.nextInt(letters.length)]);
    c5r1.setText("" + letters[random.nextInt(letters.length)]);
    c1r2.setText("" + letters[random.nextInt(letters.length)]);
    c2r2.setText("" + letters[random.nextInt(letters.length)]);
    c3r2.setText("" + letters[random.nextInt(letters.length)]);
    c4r2.setText("" + letters[random.nextInt(letters.length)]);
    c5r2.setText("" + letters[random.nextInt(letters.length)]);

Emanuel · Accepted Answer · 2017-04-17 15:18:56Z

private String[] letters = {"G","O","K","U","H","A","N","L","Z","M"};
private List<String> list = new ArrayList<String>(Arrays.asList(letters ));

private String getUniqueRandomString() {
      int i = ThreadLocalRandom.current().nextInt(0, letters.size() + 1);
      String s = letters.get(i);
      letters.remove(i);
      return s;
}
private void init() { 

    c1r1 = (Button) findViewById(R.id.btn1);
    c2r1 = (Button) findViewById(R.id.btn2);
    c3r1 = (Button) findViewById(R.id.btn3);
    c4r1 = (Button) findViewById(R.id.btn4);
    c5r1 = (Button) findViewById(R.id.btn5);
    c1r2 = (Button) findViewById(R.id.btn6);
    c2r2 = (Button) findViewById(R.id.btn7);
    c3r2 = (Button) findViewById(R.id.btn8);
    c4r2 = (Button) findViewById(R.id.btn9);
    c5r2 = (Button) findViewById(R.id.btn10);
    first = (Button) findViewById(R.id.first);
    second = (Button) findViewById(R.id.second);
    third = (Button) findViewById(R.id.third);
    fourth = (Button) findViewById(R.id.fourth);

    c1r1.setText(getUniqueRandomString());
    c2r1.setText(getUniqueRandomString());

// ... 

}

makrom · Accepted Answer · 2017-04-17 15:34:01Z

1

You can just use Collections.shuffle(List list)

edited Apr 17, 2017 at 15:34

answered Apr 17, 2017 at 15:27

makrom

3762 silver badges13 bronze badges

Comments

AAryan · Accepted Answer · 2017-04-17 15:22:26Z

0

public ArrayList<String> arrayList;

@Override
protected void onCreate (Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    arrayList=new ArrayList<String>();

    String[] letters = {"G","O","K","U","H","A","N","L","Z","M"};
    for (String s:letters)
      arrayList.add(s);



    c1r1.setText("" + getRandom());
    c2r1.setText("" + getRandom());
    ...
    ...

}


public String getRandom(){

    String randomString=arrayList.get(random.nextInt(arrayList.size()));
    arrayList.remove(randomString);
    return randomString;

}

answered Apr 17, 2017 at 15:22

AAryan

20.2k8 gold badges49 silver badges69 bronze badges

2 Comments

Emanuel Over a year ago

erm, wait. You used my solution and cleaned it up? :)

PG20 Over a year ago

Thank you both @EmanuelSeibold and Abhishek Aryan. It perfectly works :)

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