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Find first and last element of ArrayList in java

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  • Difficulty Level : Medium
  • Last Updated : 25 Aug, 2022
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Prerequisite: ArrayList in Java Given an ArrayList, the task is to get the first and last element of the ArrayList in Java, Examples:

Input: ArrayList = [1, 2, 3, 4] 
Output: First = 1, Last = 4

Input: ArrayList = [12, 23, 34, 45, 57, 67, 89] 
Output: First = 12, Last = 89

Approach:

  1. Get the ArrayList with elements.
  2. Get the first element of ArrayList with use of get(index) method by passing index = 0.
  3. Get the last element of ArrayList with use of get(index) method by passing index = size – 1.

Below is the implementation of the above approach: 

Java




// Java code to find first and last element
// of ArrayList
 
import java.util.ArrayList;
 
public class GFG {
 
    // main method
    public static void main(String[] args)
    {
 
        // creating an Empty Integer ArrayList
        ArrayList<Integer> list = new ArrayList<Integer>(5);
 
        // using add() to initialize values
        list.add(1);
        list.add(2);
        list.add(3);
        list.add(4);
 
        // printing initial value ArrayList
        System.out.print("ArrayList: " + list);
 
        // find first element
        int first = list.get(0);
 
        // find last element
        int last = list.get(list.size() - 1);
 
        // print first and last element of ArrayList
        System.out.println("\nFirst : " + first
                           + ", Last : " + last);
    }
}

Output:

ArrayList: [1, 2, 3, 4]
First : 1, Last : 4

Time Complexity: O(1)

Auxiliary Space: O(1)

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