Java LinkedList pop() method
Syntax and Examples

The pop() method in Java's LinkedList class is a powerful tool for removing and returning the first element of the list. It’s similar to how a stack operates (Last-In, First-Out), but applied to a linked list.

Syntax

public E pop()

Description

The pop() method removes and returns the first element of this linked list. It throws a NoSuchElementException if the list is empty.

Parameters

Parameter	Description
None	This method does not take any parameters.

Return Value

The pop() method returns the element that was removed from the head of the list. The return type is E, which represents the generic type of elements stored in the linked list.

Examples

Example 1: Basic Usage

This example demonstrates how to use the pop() method with a simple list of strings. We create a LinkedList and add some values, then pop off the first element.

import java.util.LinkedList;
import java.util.NoSuchElementException;

public class PopExample {
    public static void main(String[] args) {
        LinkedList<String> myList = new LinkedList<>();
        myList.add("Apple");
        myList.add("Banana");
        myList.add("Cherry");

        try {
            String firstElement = myList.pop();
            System.out.println("Popped element: " + firstElement);
            System.out.println("Remaining list: " + myList);
        } catch (NoSuchElementException e) {
            System.out.println("List is empty.");
        }
    }
}

Popped element: Apple
Remaining list: [Banana, Cherry]

Explanation: We created a LinkedList named myList and added three strings. The pop() method removed "Apple" (the first element) and assigned it to the variable firstElement. Then we printed the popped element and what's left in the list.

Example 2: Handling Empty List

This example shows how to handle the case where you try to pop from an empty LinkedList using a try-catch block. This is important because attempting to call pop() on an empty list will throw a NoSuchElementException.

import java.util.LinkedList;
import java.util.NoSuchElementException;

public class PopEmptyListExample {
    public static void main(String[] args) {
        LinkedList<Integer> emptyList = new LinkedList<>();

        try {
            Integer poppedElement = emptyList.pop();
            System.out.println("Popped element: " + poppedElement);
        } catch (NoSuchElementException e) {
            System.out.println("Cannot pop from an empty list.");
        }
    }
}

Cannot pop from an empty list.

Explanation: Here, we created a LinkedList emptyList which is initially empty. We then attempted to call the pop() method. Because the list is empty, this resulted in a NoSuchElementException being thrown. The catch block handled this exception and printed an appropriate error message.

Example 3: Using with Generic Types

This example demonstrates using pop() with different data types to showcase the generic nature of LinkedLists.

import java.util.LinkedList;
import java.util.NoSuchElementException;

public class GenericPopExample {
    public static void main(String[] args) {
        LinkedList<Double> doubleList = new LinkedList<>();
        doubleList.add(3.14);
        doubleList.add(2.71);

        try {
            Double firstDouble = doubleList.pop();
            System.out.println("Popped Double: " + firstDouble);
        } catch (NoSuchElementException e) {
           System.out.println("List is empty.");
        }
    }
}

Popped Double: 3.14

Explanation: This example shows that LinkedLists can contain any type of object, not just strings or integers. We created a list of Doubles and successfully popped the first element.