Java LinkedList addAll() method - Syntax and Examples

This reference explains LinkedList addAll() method - Syntax and Examples through its syntax, examples and boundaries. Use the linked course lessons when the surrounding Java concepts are unfamiliar.

Java LinkedList addAll() method

The addAll() method in Java's LinkedList allows you to add all elements from another collection (like an array, a set or another list) into your linked list. You can either append these elements at the end of the list or insert them at a specific index.

    public boolean addAll(Collection<? extends E> c) 

public boolean addAll(int index, Collection<? extends E> c)
    
  

Both versions of addAll() return a boolean value. It returns true if the addition was successful, and false otherwise.

This example demonstrates how to append all elements from an existing list to a linked list using the first version of addAll(). Think of it like merging two lists together.

    import java.util.*; 

public class AddAllExample1 {
    public static void main(String[] args) {
        LinkedList<String> list1 = new LinkedList<>(Arrays.asList("A", "B", "C"));

        List<String> list2 = Arrays.asList("D", "E", "F");


        boolean added = list1.addAll(list2);


        System.out.println("Added all elements: " + added);  // Output will be true.

        System.out.println(list1); // Prints the combined list.
    }
}
    
  

Added all elements: true
[A, B, C, D, E, F]

In this example, list2 (containing "D", "E", and "F") is appended to the end of list1. The resulting list contains all elements from both original lists.

This example shows how to insert all elements from one collection into another linked list at a particular position using the second version of addAll(). This is like inserting a new block of items into an existing list.

    import java.util.*; 

public class AddAllExample2 {
    public static void main(String[] args) {
        LinkedList<Integer> list1 = new LinkedList<>(Arrays.asList(1, 2, 3));

        List<Integer> list2 = Arrays.asList(4, 5, 6);


        boolean added = list1.addAll(1, list2); 


        System.out.println("Added all elements: " + added); // Output will be true.

        System.out.println(list1); // Prints the modified list.
    }
}
    
  

Added all elements: true
[1, 4, 5, 6, 2, 3]

Here, the elements of list2 (containing 4, 5, and 6) are inserted into list1 starting at index 1. The original element at index 1 (which was '2') and all subsequent elements are shifted to the right.

This example demonstrates what happens when you try to insert a collection at an invalid index, which leads to an exception.

    import java.util.*; 

public class AddAllExample3 {
    public static void main(String[] args) {
        LinkedList<String> list = new LinkedList<>(Arrays.asList("A", "B", "C"));

        List<String> toAdd = Arrays.asList("D", "E");


        try {
            list.addAll(10, toAdd); // Attempt to insert at an invalid index.

        } catch (IndexOutOfBoundsException e) {
            System.out.println("Caught IndexOutOfBoundsException: " + e.getMessage());
        }
    }
}
    
  

Caught IndexOutOfBoundsException: index out of range

Because the LinkedList only has a size of 3, attempting to insert at index 10 will throw an IndexOutOfBoundsException. It's important to make sure your index is within valid bounds (between 0 and size()).

Check the example’s types, inputs and documented behavior before copying it into an application. Some APIs require external libraries, files or platform services; consult their setup notes.

Related explanations: Java Data Types - Primitive and Non-Primitive, Java Class - Blueprint of Objects, Exceptions in Java Introduction.

Supporting documentation: Official Java learning guide.