How to Check if a Java ArrayList is Empty and Display a Message

How can I check if a Java ArrayList is empty and display a message based on its state?

import java.util.*;
import javax.swing.JOptionPane;

In Java, you can check whether an ArrayList is empty by utilizing the `isEmpty()` method, which returns `true` if the list contains no elements. This article outlines how to implement this functionality and display appropriate messages to the user using `JOptionPane`.

import java.util.*;
import javax.swing.JOptionPane;

public class ArrayListEmpty {
    public static void main(String[] args) {
        List<Integer> numbers = new ArrayList<>();
        int number;
        do {
            number = Integer.parseInt(JOptionPane.showInputDialog("Enter a number (-1 to stop):"));
            if(number != -1) {
                numbers.add(number);
            }
        } while (number != -1);
        giveList(numbers);
    }

    public static void giveList(List<Integer> numbers) {
        if (numbers.isEmpty()) {
            JOptionPane.showMessageDialog(null, "List is empty!");
        } else {
            JOptionPane.showMessageDialog(null, "List isn't empty");
        }
    }
}

Causes

• The original implementation checks if the list is `null`, which is incorrect as you should check if the list is empty instead.
• The use of `add(number)` includes the value `-1` in the list, which you might want to exclude before checking for emptiness.

Solutions

• Modify the `giveList()` method to use `numbers.isEmpty()` for checking if the list is empty.
• Avoid adding `-1` to the list and implement the exit condition correctly.

Mistake: Checking for `null` instead of using `isEmpty()` method.

Solution: Replace the null check with a call to `numbers.isEmpty()`.

Mistake: Adding `-1` to the list, which affects the check for emptiness.

Solution: Implement a conditional to add numbers to the list only if they are not `-1`.