Convert an Iterator to a List in Java

Find first and last element of ArrayList in java

Last Updated : 25 Aug, 2022

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:

Get the ArrayList with elements.
Get the first element of ArrayList with use of get(index) method by passing index = 0.
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)

Convert an Iterator to a List in Java

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