Non duplicates numbers in user input

Question

I am trying to work out how to create an input validation where it won\'t let you enter the same number twice as well as being inside a range of numbers and that nothing can be

Answer 1

I hope it will help , upvote if yes

import java.util.ArrayList;
import java.util.Scanner;
public class Test {
private ArrayList choose() {
Scanner scanner = new Scanner(System.in);
ArrayList alreadyEntered = new ArrayList<>(6); // using six because your loop indicated me that you're taking six digits 
for(int i = 0 ; i < 6 ; ++i){ // ++i is more efficient than i++
    System.out.println("Enter a number between 1 & 59");
    String digit;
    digit = scanner.nextLine().trim();
    if(digit.matches("[1-5][0-9]|[0-9]" && !alreadyEntered.contains(digit))// it checks if it is a number as well as if it is in range as well if it is not already entered, to understand this learn about regular expressions
    alreadyEntered.add(digit);
    else {
      System.out.println("Invalid input, try again");
      --i;
    }
 }
 return alreadyEntered // return or do whatever with the numbers as i am using return type in method definition i am returning
}

 scanner.close();
 } 

using arraylist of string just to make things easy otherwise i would have to to some parsing from integer to string and string to integer