Java 9 ArrayList add, set and remove element

John D K -

Java ArrayList has useful methods for adding, setting and removing new elements:

  • list.add("Bing");
  • list.set(0, "DuckDuckGo");
  • list.remove(2);

You can check also:

Adding new element to ArrayList Java

ArrayList is dynamic unlike Array and you can add elements dynamically:

import java.util.ArrayList;

ArrayList<String> list = new ArrayList<>();
list.add("Yahoo");      // [0]
list.add("Google");     // [1]
list.add("Bing");       // [2]

result:

Yahoo
Google
Bing

Set new value to ArrayList Java

You can set new values to ArrayList by index:

import java.util.ArrayList;

ArrayList<String> list = new ArrayList<>();
list.add("Yahoo");      // [0]
list.add("Google");     // [1]
list.add("Bing");       // [2]

list.set(0, "DuckDuckGo");
list.set(1, "Baidu");
list.set(2, "Yandex");

result:

DuckDuckGo
Baidu
Yandex

Note: If you give an not existing index in the array you will get: > java.lang.IndexOutOfBoundsException: Index: 1, Size: 1

Remove item from ArrayList by index

Deleting ArrayList item is easy but could be tricky:

import java.util.ArrayList;

ArrayList<String> list = new ArrayList<>();

list.add("Yahoo");      // [0]
list.add("Google");     // [1]
list.add("Bing");       // [2]

list.remove(0);
list.remove(1);

for (String value : list) {
    System.out.println(value);
}

result:

Google

Note: In this example we are deleting [0] and [1] but at the end we get: Google which is item - 1. This is because the second remove is applied on changed ArrayList. If you want to delete [0] and [1] of the original list you have to delete [0] twice.

Again wrong index produce error:

Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 2, Size: 2

Remove item from ArrayList by value

You can remove element by value (in case of non existing value then nothing is changed to ArrayList):

import java.util.ArrayList;

ArrayList<String> list = new ArrayList<>();

list.add("Yahoo");
list.add("Google");
list.add("Bing");

list.remove("Yahoo");
list.remove("Google");

for (String value : list) {
    System.out.println(value);
}

result:

Bing