Java Program to Access the Part of List as List

06 Jul, 2021
A List is an ordered sequence of elements stored together to form a collection. A list can contain duplicate as well as null entries. A list allows us to perform index-based operations, that is additions, deletions, manipulations, and positional access. Java provides an in-built interface <<java.util>> to perform list as well as other class-based functions. 
Methods:
The naive approach by maintaining the start and end index.Using subList() method.
The naive approach by maintaining the start and end index.
Using subList() method.
Method 1
Elements are accessed at the required indexes of the list.Add them to a new empty list created.The start and end index values are used to access the part of the list required. By default, the indexes are assumed to start at 0.
Elements are accessed at the required indexes of the list.
Add them to a new empty list created.
The start and end index values are used to access the part of the list required. By default, the indexes are assumed to start at 0.
This approach requires an additional space of maintaining a new list to store the sublist desired.
Example
Java
// Java Program to Access the Part of List as List // Importing utility and input/output java classesimport java.util.*;import java.io.*;// Importing Iterator classimport java.util.Iterator; // Classpublic class GFG {     // Main driver method    public static void main(String[] args)    {         // Declaring a list        List<Integer> list1 = new ArrayList<Integer>();         // Adding elements to list1        list1.add(1);        list1.add(7);        list1.add(8);        list1.add(2);        list1.add(11);        list1.add(3);        list1.add(66);        list1.add(30);         // Print the original List        System.out.println("The original list contents : ");         Iterator iterator = list1.iterator();         // Iterating over elements using hasNext()        // which holds true till        // there is further more element in the List        while (iterator.hasNext()) {            System.out.print(iterator.next() + " ");        }         // Declaring a new List to store sublist        List<Integer> new_list = new ArrayList<Integer>();         // Maintaining and Setting counter to zero        int i = 0;         // Specifying the positions of the list to access        // custom        int start_indx = 2, end_indx = 5;         // Condition check which holds true till        // current counter value is less than size of List        while (i < list1.size()) {             // Checking if counter is in range of start and            // end indx            if (i >= start_indx && i <= end_indx) {                 // Adding element to new List                new_list.add(list1.get(i));            }             // Incrementing counter            i++;        }         // Print all element of List        System.out.println();         // Display message        System.out.println("The sublist contents : ");         // Iterator        iterator = new_list.iterator();         // Iterating over elements using hasNext() method        // which holds true till further element is        // remaining in List else returns false        while (iterator.hasNext()) {             // Print the elements of subList            System.out.print(iterator.next() + " ");        }    }}
  
The original list contents : 
1 7 8 2 11 3 66 30 
The sublist contents : 
8 2 11 3
Time Complexity = O(n)
Space Complexity = O(n) where n is the size of the list.
 
Method 2: Java provides us with an in-built method sublist() to access the elements belonging to the specified range of index values. The method is provided by the ArrayList package.
 
Syntax : 
 
public List subList(int fromIndex, int toIndex)
 
Parameters: 
 
fromIndex = start index
toIndex = endIndex
 
Return Type: A list of the required elements. The method access all the elements in the range fromIndex to toIndex-1. If fromIndex is equal to toIndex, an empty list is returned. 
 
Example:
 
Java
// Java Program to Access the Part of List as List // Importing java utility package, and// all classes of input/output libraryimport java.util.*;import java.util.Iterator;import java.io.*; class AccessSublist {     // Main driver method    public static void main(String[] args)    {         // Declaring a List of String type        List<String> list1 = new ArrayList<String>();         // Adding elements to above List(List1)        // Custom inputs        list1.add("Are");        list1.add("you");        list1.add("working!");        list1.add("hard");        list1.add("Geeeks?");         // Display message        System.out.print("The original list contents : ");         // Iterator        Iterator iterator = list1.iterator();         // Iterating over elements using hasNext()        // which holds true till there is        // further more element present in List        while (iterator.hasNext()) {             // Print the original List            System.out.print(iterator.next() + " ");        }         // Extracting the contents of the list        // index between 0 and 2 (custom)        List<String> new_list = list1.subList(0, 3);         // Print        System.out.println();         // Display message        System.out.print("The sublist contents : ");         // Iterator        iterator = new_list.iterator();         // Iterating over elements using hasNext()        // which holds true till there is        // further more element present in List        while (iterator.hasNext()) {             // Print the sublist(list2)            System.out.print(iterator.next() + " ");        }    }}
  
The original list contents : Are you working! hard Geeeks? 
The sublist contents : Are you working!
 
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