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

// 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

// 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

// 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());         }     } }

Output

Error: toIndex = 5

Explanation: In this example, the toIndex exceeds the size of the list.

ArrayList to Array Conversion in Java : toArray() Methods

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