Java ArrayList.subList() Method

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

The subList() method is used to get a portion of this list between the specified fromIndex, inclusive, and toIndex, exclusive. If fromIndex and toIndex are equal, the returned list is empty.
The returned list is backed by this list, so non-structural changes in the returned list are reflected in this list, and vice-versa. The returned list supports all of the optional list operations.

This method eliminates the need for explicit range operations (of the sort that commonly exist for arrays). Any operation that expects a list can be used as a range operation by passing a subList view instead of a whole list. For example, the following idiom removes a range of elements from a list:

list.subList(from, to).clear();

Package: java.util

Java Platform:Java SE 8

Syntax:

subList(int fromIndex, int toIndex)

Parameters:

Return Value:

a view of the specified ranges within this list

Throws:

• IndexOutOfBoundsException - if an endpoint index value is out of range (fromIndex < 0 || toIndex > size)
• IllegalArgumentException - if the endpoint indices are out of order (fromIndex > toIndex)

Pictorial presentation of ArrayList.subList() Method

Example: Java ArrayList.subList Method

In the following example the subList() method is used to get a portion of this list between the specified fromIndex, inclusive, and toIndex.

import java.util.*;

public class test {
   public static void main(String[] args) {
      
    // create an empty array list 
    ArrayList<String> color_list = new ArrayList<String>();

    // use add() method to add values in the list
    color_list.add("White");
    color_list.add("Black");
	color_list.add("Red");
	color_list.add("Green");
    color_list.add("Yellow");
    System.out.println("List of the colors :" + color_list);
   
   //Return portion of the list : fromindex(inclusive)->1,  toindex(exclusive)->3
     ArrayList<String> new_color_list1 = new ArrayList<String>(color_list.subList(1, 3));
     System.out.println("Portion of the list: "+new_color_list1);

   //Return empty list as fromindex and toindex are equal
     ArrayList<String> new_color_list2 = new ArrayList<String>(color_list.subList(3, 3));
     System.out.println("Portion of the list: "+new_color_list2);
  }
}

Output:

F:\java>javac test.java

F:\java>java test
List of the colors :[White, Black, Red, Green, Yellow]
Portion of the list: [Black, Red]
Portion of the list: []

Example of Throws: subList(int fromIndex, int toIndex) Method

IndexOutOfBoundsException - if an endpoint index value is out of range (fromIndex < 0 || toIndex > size)
IllegalArgumentException - if the endpoint indices are out of order (fromIndex > toIndex)

Let

ArrayList new_color_list1 = new ArrayList(color_list.subList(1, 8));

in the above example.

Output:

List of the colors :[White, Black, Red, Green, Yellow] 
Exception in thread "main" java.lang.IndexOutOfBoundsEx
ception: toIndex = 8                                   
        at java.util.ArrayList.subListRangeCheck(ArrayL
ist.java:962)                                          
        at java.util.ArrayList.subList(ArrayList.java:9
54)                                                    
        at test.main(test.java:18

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