We can copy and add List items in Array List using addAll() method. This method accepts a Collection (Ex. List) as an argument and adds the collection items at the end of its calling Collection (Ex. ArrayList). This method returns a boolean value. addAll() return true if the collection successfully adds else it returns false.
We can clone the list by two ways:
- Using addAll() method
- Using a copy constructor
Method 1: Using addAll() method
Syntax:
public boolean addAll(Collection c);
Parameter: It accepts a collection to be cloned as its parameter
Return Value: This method returns a boolean value. addAll() return true if the collection successfully adds else it returns false.
Exception: It will throw Null Pointer Exception if the specified Collection is null.
Java
// Java program to clone the list import java.util.ArrayList;import java.util.List; public class GFG { public static void main(String[] args) { // create ArrayList ArrayList<String> ArrList = new ArrayList<String>(); // Adding elements to the ArrayList ArrList.add("item 1"); ArrList.add("item 2"); ArrList.add("item 3"); System.out.println("ArrayList = " + ArrList); // create List List<String> ListItem = new ArrayList<String>(); ListItem.add("item 4"); ListItem.add("item 5"); // add List items in ArrayList ArrList.addAll(ListItem); System.out.println( "After Adding List Item in ArrayList = "+ ArrList); }} |
ArrayList = [item 1, item 2, item 3] After Adding List Item in ArrayList = [item 1, item 2, item 3, item 4, item 5]
Method 2: Using a copy constructor
Using the ArrayList constructor in Java, a new list can be initialized with the elements from another collection.
Syntax:
ArrayList arrlist = new ArrayList(collection c);
Here, c is the collection containing elements to be added to this list.
Approach:
- Create a list to be cloned.
- Clone the list bypassing the original list as the parameter of the copy constructor of ArrayList.
Java
// Program to clone a List in Java import java.util.ArrayList; import java.util.Arrays; import java.util.List; class Example { public static void main(String[] args) { // Create a list List<String> original = Arrays.asList( "GeeksForGeeks", "Coding", "Portal"); // Clone the list List<String> cloned_arraylist = new ArrayList<String>(original); System.out.println(cloned_arraylist); } } |
[GeeksForGeeks, Coding, Portal]
