ArrayList clone() method in Java

In this tutorial, we will see examples of ArrayList clone() method. This method creates a shallow copy of an ArrayList.

Syntax:

newList = oldList.clone()

Creates a shallow copy of oldList and assign it to newList.

Example 1: Creating a copy of an ArrayList using clone()

In this example, we have an ArrayList of String type and we are cloning it to another ArrayList using clone() method. The interesting point to note here is that when we added and removed few elements from original ArrayList al after the clone() method, the another ArrayList al2 didn’t get affected. It shows that clone() method just returns a shallow copy of ArrayList.

import java.util.ArrayList;
public class Details {

   public static void main(String a[]){
     ArrayList<String> al = new ArrayList<String>();

     //Adding elements to the ArrayList
     al.add("Apple");
     al.add("Orange");
     al.add("Mango");
     al.add("Grapes");
     System.out.println("ArrayList: "+al);

     ArrayList<String> al2 = (ArrayList<String>)al.clone();
     System.out.println("Shallow copy of ArrayList: "+ al2);

     //add and remove from original ArrayList
     al.add("Fig");
     al.remove("Orange");

     //print both ArrayLists after add & remove
     System.out.println("Original ArrayList:"+al);
     System.out.println("Cloned ArrayList:"+al2);
   }
}

Output:

ArrayList: [Apple, Orange, Mango, Grapes]
Shallow copy of ArrayList: [Apple, Orange, Mango, Grapes]
Original ArrayList:[Apple, Mango, Grapes, Fig]
Cloned ArrayList:[Apple, Orange, Mango, Grapes]

Example 2: Clone Integer ArrayList

In the following example, we are creating a shallow copy of an Integer ArrayList using clone() method. This example is similar to the first example, except that here list contains integers.

import java.util.ArrayList;
public class JavaExample {

  public static void main(String args[])
  {
    // Creating an ArrayList
    ArrayList<Integer> numbers = new ArrayList<Integer>();

    // Adding elements to the arraylist
    numbers.add(3);
    numbers.add(7);
    numbers.add(5);
    numbers.add(11);
    numbers.add(9);

    // print first ArrayList
    System.out.println("Original ArrayList: "+ numbers);

    // Creating another ArrayList
    // Copying the array list "numbers" to this list
    ArrayList<Integer> copyList = (ArrayList<Integer>)numbers.clone();

    // Displaying the other linked list
    System.out.println("Second ArrayList: "+ copyList);
  }
}

Output:

Original ArrayList: [3, 7, 5, 11, 9]
Second ArrayList: [3, 7, 5, 11, 9]

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