Append elements at the end of a List in Java

This post will discuss how to append elements at the end of a List in Java.

1. Using `List.add()` method

The standard solution to append an element to the end of a list is using the List.add() method, which takes the element to be inserted. Following is a simple example demonstrating the usage of this method:

import java.util.ArrayList;

import java.util.Arrays;

import java.util.List;

class Main

{

public static void main(String[] args)

{

List<String> alphabets = new ArrayList<>(Arrays.asList("A", "B", "C", "D"));

String e = "E";

alphabets.add(e);

System.out.println(alphabets);

}

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Output:

[A, B, C, D, E]

The List interface provides an overloaded version of the add() method, which additionally takes the index at which the specified element is to be inserted. To insert at the end, pass the list’s size as an index to it.

import java.util.*;

class Main

{

public static void main(String[] args)

{

List<String> alphabets = new ArrayList<>(Arrays.asList("A", "B", "C", "D"));

String e = "E";

alphabets.add(alphabets.size(), e);

System.out.println(alphabets);

}

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Output:

[A, B, C, D, E]

2. Using `List.addAll()` method

If you want to insert multiple elements at the end of a list, the addAll() method might come in handy. It appends all elements in the collection to the end of the list, in the iteration order. For example,

import java.util.*;

class Main

{

public static void main(String[] args)

{

List<String> alphabets = new ArrayList<>(Arrays.asList("A", "B", "C", "D"));

List<String> collection = Arrays.asList("E", "F", "G");

alphabets.addAll(collection);

System.out.println(alphabets);

}

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Output:

[A, B, C, D, E, F, G]

If you want to insert only a single element, you can pass a singleton collection.

import java.util.*;

class Main

{

public static void main(String[] args)

{

List<String> alphabets = new ArrayList<>(Arrays.asList("A", "B", "C", "D"));

String e = "E";

alphabets.addAll(Collections.singleton(e));

System.out.println(alphabets);

}

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Output:

[A, B, C, D, E]

3. Using `Deque.addLast()` method

The Deque data structure is optimized to insert an element at the front and end in constant time. All Deque implementations contain the addLast() method, which adds the specified element at the end of the deque.

import java.util.ArrayDeque;

import java.util.Arrays;

import java.util.Deque;

class Main

{

public static void main(String[] args)

{

Deque<String> alphabets = new ArrayDeque<>(Arrays.asList("A", "B", "C", "D"));

String e = "E";

alphabets.addLast(e); // or add() method

System.out.println(alphabets);

}

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Output:

[A, B, C, D, E]

That’s all about appending elements at the end of a List in Java.

Append elements at the end of a List in Java

1. Using List.add() method

2. Using List.addAll() method

3. Using Deque.addLast() method

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1. Using `List.add()` method

2. Using `List.addAll()` method

3. Using `Deque.addLast()` method