How to Remove Element from ArrayList in Java - Simple Guide

To remove an ArrayList element in Java, use the remove() method. You can remove by index using remove(int index) or by value using remove(Object o).

Syntax

The ArrayList class provides two main remove() methods:

• remove(int index): Removes the element at the specified position (index) in the list.
• remove(Object o): Removes the first occurrence of the specified element from the list.

Indexes start at 0, so the first element is at index 0.

java

arrayList.remove(2); // removes element at index 2
arrayList.remove("apple"); // removes first "apple" element

Example

This example shows how to remove elements by index and by value from an ArrayList of strings.

java

import java.util.ArrayList;

public class RemoveElementExample {
    public static void main(String[] args) {
        ArrayList<String> fruits = new ArrayList<>();
        fruits.add("apple");
        fruits.add("banana");
        fruits.add("cherry");
        fruits.add("date");
        fruits.add("apple");

        System.out.println("Original list: " + fruits);

        // Remove element at index 1 ("banana")
        fruits.remove(1);
        System.out.println("After removing index 1: " + fruits);

        // Remove first occurrence of "apple"
        fruits.remove("apple");
        System.out.println("After removing first 'apple': " + fruits);
    }
}

Output

Original list: [apple, banana, cherry, date, apple]
After removing index 1: [apple, cherry, date, apple]
After removing first 'apple': [cherry, date, apple]

Common Pitfalls

Common mistakes when removing elements from an ArrayList include:

• Using remove(int index) when you mean to remove by value, which can cause unexpected removals if the list contains integers.
• Trying to remove an element that does not exist, which returns false but does not throw an error.
• Modifying the list while iterating over it without using an iterator, which causes ConcurrentModificationException.

java

import java.util.ArrayList;

public class RemovePitfall {
    public static void main(String[] args) {
        ArrayList<Integer> numbers = new ArrayList<>();
        numbers.add(1);
        numbers.add(2);
        numbers.add(3);

        // Wrong: removes element at index 2, not the number 2
        numbers.remove(2);
        System.out.println("After remove(2): " + numbers); // Output: [1, 2]

        // Right: remove object 2 by casting to Integer
        numbers.remove(Integer.valueOf(2));
        System.out.println("After remove(Integer.valueOf(2)): " + numbers); // Output: [1, 3]
    }
}

Output

After remove(2): [1, 2]
After remove(Integer.valueOf(2)): [1, 3]

Quick Reference

Here is a quick summary of how to remove elements from an ArrayList:

Method	Description	Example
remove(int index)	Removes element at the given index	list.remove(0); // removes first element
remove(Object o)	Removes first occurrence of the object	list.remove("apple"); // removes first "apple"
clear()	Removes all elements from the list	list.clear(); // list becomes empty

Key Takeaways

Use remove(int index) to delete element by position in the list.

Use remove(Object o) to delete element by value; it removes the first match.

Be careful with remove(int) on lists of Integer to avoid confusion between index and value.

Removing elements while iterating requires using an iterator to avoid errors.

If the element to remove does not exist, remove(Object) returns false but does not throw an error.