Remove blank spaces from arraylist

Question

I have just started studying Computer Science, and we have just started our first Java project. It is a information system that should keep tracks of our friends.

I have made an arraylist where I can put in some interests that our friends have. The problem is that I can easily enter blank spaces and just press enter to insert an "empty" element into the array list. I have tried using different methods to remove them from the array list, and haven't come to an answer. Under here is the code that I am stuck with.

I have set the program to exit when I enter "exit", and that works perfectly fine. At the start when I typed in "exit", then the program would include the "exit" into the array, but after I added the checklist() method, I was able to keep "exit" out of the array list. I just can't seem to make it work with spaces and Enters.

package testing;

import java.util.ArrayList;
import java.util.Scanner;

public class Test {

public static void main(String[] args) {
    ArrayList<String> interests = new ArrayList<String>();
    String interest;
    String quit = "exit";
    do {
        Scanner userInput =  new Scanner(System.in);
        System.out.println("Write interest: ");
        interest = userInput.nextLine();
        if (interest.isEmpty()) { // Makes sure you cant press ENTER.
            System.out.println("You just entered SPACE, please write an interest: ");
            interest = userInput.nextLine();
        }  else if (interest.isBlank()) { // Makes sure you cant enter a plain space.
            System.out.println("You just entered a plain space, please write an interest: ");
            interest = userInput.nextLine();
        }
        interests.add(interest);
    } while (!interest.equals(quit));
    checkList(interests);
    System.out.println(interests);
}

public static void checkList(ArrayList<String> interests) {
    String quit = "exit";
    for (int i = 0; i < interests.size(); i++) {
        if(interests.get(i).isBlank()) {                
            interests.remove(i);
            System.out.println("Position: " + i + " is a blank space");
            System.out.println("Removed blank space: " + interests.get(i));
        } else if (interests.get(i).isEmpty()) {
            interests.remove(i);
            System.out.println("Position: " + i + " is a ENTER");
            System.out.println("Removed ENTER: " + interests.get(i));
        } else if (interests.get(i).equals(quit)) {
            interests.remove(i);
        }
    }
}

}

score 1 · Answer 1 · edited Oct 03 '20 at 10:13

1

I already managed to find the answer to my question. The solution was to use this instead of using the method checkList().

interests.removeAll(Arrays.asList("", null, " ", "exit"));

edited Oct 03 '20 at 10:13

Mark Rotteveel

100,966
191
140
197

answered Oct 02 '20 at 21:34

Lasse Jonassen

23
10

String.trim() is better. Check your solution against tabs and newlines. – MarsAtomic Oct 02 '20 at 21:42

score -1 · Answer 2 · answered Oct 02 '20 at 21:33

-1

I am not familier with Java. But i think the best concept would be to block an input from empty space. So a user needs to enter data into an array. Just check if string is null || empty

answered Oct 02 '20 at 21:33

ddave

19
3

Look at the my answer below. There is the solution. – Lasse Jonassen Oct 02 '20 at 21:34
Checking with String.isEmpty() isn't enough. That method returns true if the String in question has a length of zero. What if someone enters " ", which is a single space, and therefore, not empty? That's exactly the case that OP complains about. What about "\t\t\t" or "\n\t\n "? None of those are empty, but they are whitespace and they'll break the program. Be careful when answering questions on languages where you lack proficiency -- things may not work the same as they do in languages with which you are familiar. Also, answers on this site are supposed to be definitive. Please don't guess. – MarsAtomic Oct 02 '20 at 21:40

Remove blank spaces from arraylist

2 Answers2