Java ArrayList subList() Method

Last Updated : 12 Dec, 2024

The subList() method of the ArrayList class in Java is used to retrieve a portion of an ArrayList between specified indices. When we perform any modifications to the sub list, that will reflect in the original list and vice versa.

Example 1: Here, we use the subList() method to extract a sublist from an ArrayList.

// Java program to demonstrate subList()
// by extracting a portion of the ArrayList
import java.util.ArrayList;
import java.util.List;

public class GFG {
    public static void main(String[] args) {
      
        // Creating an ArrayList of flowers
        ArrayList<String> l = new ArrayList<>();
        l.add("Rose");
        l.add("Lotus");
        l.add("Lavender");
        l.add("Lilly");
        l.add("Sunflower");

        // Extracting a sublist
        List<String> s = l.subList(1, 4);

        // Printing the original list and sublist
        System.out.println("" + l);
        System.out.println("" + s);
    }
}

Output

[Rose, Lotus, Lavender, Lilly, Sunflower]
[Lotus, Lavender, Lilly]

Syntax of ArrayList subList() Method

public List<E> subList(int fromIndex, int toIndex)

Parameters:

fromIndex: Starting index (inclusive) of the sublist.
toIndex: Ending index (exclusive) of the sublist.

Returns Value: It returns a view of the portion of this list between the specified indices.

Exception: This method throws the following Exceptions.

IndexOutOfBoundsException: If an endpoint index value is out of range (fromIndex > size).
IllegalArgumentException: If an endpoint indices are out of order (fromIndex > toIndex).

Example 2: Here, we will modify a sublist and will see how the changes reflect in the original list.

// Java program to demonstrate subList()
// by modifying elements in the sublist
import java.util.ArrayList;
import java.util.List;

public class GFG {
    public static void main(String[] args) {
      
        // Creating an ArrayList of numbers
        ArrayList<Integer> n = new ArrayList<>();
        n.add(1);
        n.add(2);
        n.add(3);
        n.add(4);
        n.add(5);

        // Creating a sublist
        List<Integer> s = n.subList(1, 4);

        // Modifying the sublist
        s.set(0, 9); // Updating the first element in sublist
        s.remove(2);  // Removing the last element in sublist

       
        System.out.println("Original List After Modification: " + n);
        System.out.println("Modified Sublist: " + s);
    }
}

Output

Original List After Modification: [1, 9, 3, 5]
Modified Sublist: [9, 3]

Explanation: In the above example, we have created the original list starts with 5 elements i.e. [1, 2, 3, 4, 5]. The sublist created using subList(1, 4) contains 3 elements [2, 3, 4]. After modifications, the original list becomes [1, 99, 3, 5], and the sublist becomes [99, 3].

Example 3: Here, we will try to use invalid indices and handle the IndexOutOfBoundsException.

// Java program to demonstrate 
// IndexOutOfBoundsException in subList()
import java.util.ArrayList;

public class GFG {
    public static void main(String[] args) {
      
        // Creating an ArrayList of names
        ArrayList<String> n = new ArrayList<>();
        n.add("Sweta");
        n.add("Gudly");

        try {
          
            // Trying to create a sublist 
            // with invalid indices
            n.subList(1, 5);
        } catch (IndexOutOfBoundsException e) {
            System.out.println("Error: " + e.getMessage());
        }
    }
}