How to get sublist of List in Java?

In Java, a List is an interface that stores elements of the same type. You can retrieve a sub-list from a List in Java. A sub-list is the view of a portion (or part) of the List. For example, if the given list is {a, b, c, d, e}, then the possible sub-lists can be {a, b}, {a, b, c}, {b, c, d}, {d, e}, etc.

The List interface in Java provides a built-in method named subList(), which returns a sub-list from the given List. We just need to specify the range of extraction.

Sublist from a List using the subList() Method

The subList() method of the List interface returns a portion (i.e., sub-list) of the original list between the specified range, which is fromIndex to toIndex. In the obtained sub-list, the element at fromIndex will be included, and at toIndex will be excluded.

Following is the syntax of the subList() method:

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

Here,

• fromIndex: The starting index (inclusive) from which the sub-list will begin extracting elements.
• toIndex: The last index (not included) up to which the sub-list will be extracted.

Example

In the following example, we use the subList() method to get a sub-list from an List {1, 2, 3, 4, 5} between the specified range 0 to 4:

import java.util.ArrayList;
import java.util.ArrayList;
import java.util.List;
public class getSublist {
   public static void main(String[] args) {
   
      //instantiating a List using ArrayList class
      List<Integer> list = new ArrayList<>();
      
      //adding elements
      list.add(1);
      list.add(2);
      list.add(3);
      list.add(4);
      list.add(5);
      
      System.out.println("The original list is: " + list);
      
      //range
      int fromIndex = 0;
      int toIndex = 4;
      System.out.println("The range is: " + fromIndex + ", " + toIndex);
      
      // Get the subList using subList() method
	  
      List<Integer> subList = list.subList(fromIndex, toIndex);
      System.out.println("The sublist elements are: " + subList);
   }
}

Below is the output of the above program:

The original list is: [1, 2, 3, 4, 5]
The range is: 0, 4
The sublist elements are: [1, 2, 3, 4]

Adding a List Element to another List

We can get a sub-list by adding a specific range of elements from one List to another List. The resultant list will be the desired sub-list.

The add() method of the List interface appends the specified element to the end of the list. Therefore, to get a sublist of a List, we need to iterate through the (original) list at any position using a for loop and add those elements to a new list (i.e., sub-list) using the add() method.

Example

In the example below, we add elements from the original List to a new List (i.e., sub-list) from index 1. To do this, we iterate through the original list starting from index 1 and add each element to the sub-list using the add() method:

import java.util.ArrayList;
import java.util.List;
public class getSublist  {
   public static void main(String[] args) {

      //instantiating a List using an ArrayList class
      List<String> vowels = new ArrayList<>();

      //adding elements
      vowels.add("A");
      vowels.add("E");
      vowels.add("I");
      vowels.add("O");
      vowels.add("U");

      System.out.println("The original list is: " + vowels);

      //creating another List
      List<String> subList = new ArrayList<>();
      for(int i = 1; i<vowels.size(); i++){
         subList.add(vowels.get(i));
      }
      
      System.out.println("The subList elements are: " + subList);
   }
}

Following is the output of the above program:

The original list is: [A, E, I, O, U]
The subList elements are: [E, I, O, U]