Java LinkedList peekLast() Method

Java LinkedList Java LinkedList

peekLast()is a [method] in JavaLinkedListmethod provided by the class, used to view but not remove the last element of the linked list. If the linked list is empty, this method returnsnull。

Syntax Format

E peekLast()

Method Characteristics

1. Non-destructive operation

peekLast()The method only views the last element of the linked list and does not remove that element from the linked list.

2. Empty linked list handling

When the linked list is empty,peekLast()it returnsnulland does not throw an exception.

3. Time complexity

SinceLinkedListis a doubly linked list implementation,peekLast()the time complexity of the method is O(1).

Method Parameters and Return Value

Parameters

This method does not accept any parameters.

Return Value

  • Returns the last element of the linked list.
  • If the linked list is empty, it returnsnull

Usage Examples

Basic Usage

Example

import java.util.LinkedList;

public class PeekLastExample {
    public static void main(String[] args) {
        LinkedList<String> list = new LinkedList<>();
       
        list.add("Apple");
        list.add("Banana");
        list.add("Cherry");
       
        String lastElement = list.peekLast();
        System.out.println("Last element: " + lastElement);  // Output: Cherry
        System.out.println("LinkedList after peek: " + list);  // The linked list remains unchanged
    }
}

Empty Linked List Case

Example

import java.util.LinkedList;

public class EmptyListExample {
    public static void main(String[] args) {
        LinkedList<String> emptyList = new LinkedList<>();
       
        String result = emptyList.peekLast();
        System.out.println("Result from empty list: " + result);  // Output: null
    }
}

Comparison of Related Methods

Method Name Function Description Behavior When the Linked List Is Empty Whether the Linked List Is Modified
peekLast() View the last element Returns null no
getLast() Get the last element Throws an exception no
removeLast() Remove and return the last element Throws an exception Yes
pollLast() Remove and return the last element Returns null Yes

Practical Application Scenarios

1. Checking the Queue Tail

When implementing a queue or deque, you can usepeekLast()to check the element at the tail of the queue without removing it.

2. Conditional Processing

When processing linked list data, you can first check whether the last element meets certain conditions before deciding whether to perform subsequent operations.

3. Logging

When you need to record the most recently added element of the linked list but do not want to remove it, you can use this method.

Notes

  1. Null value handling: SincepeekLast()may returnnull, you should perform a null check before using the return value.

  2. Concurrent environment：LinkedListis not thread-safe. UsingpeekLast()in a multi-threaded environment requires additional synchronization measures.

  3. Alternative method: If you need to ensure that the linked list is not empty, consider usinggetLast(), but note that it throws when the linked list is emptyNoSuchElementException。

Summary

peekLast()The method isLinkedLista practical utility method in the class, providing a safe way to view the last element of the linked list without modifying the linked list. Understanding this method and its differences from related methods can help developers use theLinkedListclass more effectively.

Java LinkedList Java LinkedList

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