LinkedList addAll() Method in Java
In Java, the addAll() method of the LinkedList class is used to add all the elements of one collection to another. This method takes a Collection as an argument and adds all its elements to the end of the list.
Example: Here, we use the addAll() method to add all the elements of one collection to another.
// Java Programm to demonstrate the
// working of addAll() in LinkedList
import java.util.LinkedList;
public class Geeks {
public static void main(String args[]) {
// Create an empty LinkedList
LinkedList<String> l1 = new LinkedList<>();
// Use add() method to add
// elements in the list
l1.add("Geeks");
l1.add("for");
l1.add("Geeks");
// Created another list
LinkedList<String> l2 = new LinkedList<>();
l2.add("10");
l2.add("20");
System.out.println("" + l1);
// Appending the collection
// to the list
l1.addAll(l2);
System.out.println("" + l1);
}
}
Output
[Geeks, for, Geeks] [Geeks, for, Geeks, 10, 20]
Now there are two versions of LinkedList addAll() method i.e. one with the specified index and one without any specified index.
1. addAll(Collection)
The addAll() method takes a Collection as an argument and adds all elements from the specified collection to the end of the current LinkedList.
Syntax:
public boolean addAll(Collection)
Parameters:
- list is the current LinkedList.
- Collection is the group of items whose elements will be added to the end of the current list.
Return Type: This method returns true, if at least one action of append is performed.
Example: Here, we use addAll() method to add all the elements of one collection to another at the end of the list.
// Add all the elements of one collection to another
import java.util.LinkedList;
public class Geeks {
public static void main(String args[]) {
// Create an empty list
LinkedList<Integer> l1 = new LinkedList<>();
// Use add() method to add
// elements in the list
l1.add(100);
l1.add(200);
l1.add(300);
// Create another list
LinkedList<Integer> l2 = new LinkedList<>();
l2.add(400);
l2.add(500);
l2.add(600);
System.out.println("" + l1);
// Appending the collection to the list
l1.addAll(l2);
System.out.println("" + l1);
}
}
Output
[100, 200, 300] [100, 200, 300, 400, 500, 600]
2. addAll(index , Collection)
The addAll(index , Collection) method takes an index and a Collection as arguments and adds all elements from the specified collection starting at the given index. The subsequent elements are shifted to the right.
Syntax:
public boolean.addAll(index , Collection);
Parameters: This function accepts two parameters an index and Collection. The elements of the collection are inserted at the specified index in the list.
Example: Here, we use the addAll() method to add all the elements from a collection at the specified index.
// Add all the elements from a
// collection at the specified index
import java.util.ArrayList;
import java.util.LinkedList;
class Geeks {
public static void main(String[] args) {
// Create an empty list
LinkedList<Integer> l1 = new LinkedList<>();
// Use add() to insert elements
// in the list
l1.add(100);
l1.add(200);
System.out.println("" + l1);
// Create another collection (ArrayList)
ArrayList<Integer> l2 = new ArrayList<>();
l2.add(300);
l2.add(400);
// use addAll() to add all
// elements from l2 at index 1
l1.addAll(1, l2);
System.out.println("" + l1);
}
}
Output
[100, 200] [100, 300, 400, 200]
