Add element to the beginning of linked list in Java using addFirst() method of LinkedList class

Use the addFirst() method of the LinkedList class to add elements to the beginning of the linked list in Java

The linked list is a common data structure that consists of a series of nodes, each node contains a data element and a reference to the next node. The head of the linked list points to the first node, and the pointer to the tail node is empty.

In Java, we can use the LinkedList class to implement the function of a linked list. LinkedList is a class in the Java collection framework. It implements the List interface and the Deque interface, and has operation methods such as adding, deleting and getting elements.

In the LinkedList class, there is a special addFirst() method, which can insert an element at the beginning of the linked list. The following is a sample code:

import java.util.LinkedList;

public class LinkedListExample {
    public static void main(String[] args) {
        // 创建一个空的链表
        LinkedList<String> linkedList = new LinkedList<>();

        // 添加元素到链表的开头
        linkedList.addFirst("Element 1");
        linkedList.addFirst("Element 2");
        linkedList.addFirst("Element 3");

        // 打印链表的所有元素
        System.out.println("链表的元素：" + linkedList);

        // 获取链表的第一个元素
        String firstElement = linkedList.getFirst();
        System.out.println("链表的第一个元素：" + firstElement);

        // 删除链表的第一个元素
        linkedList.removeFirst();

        // 打印链表的所有元素
        System.out.println("删除第一个元素后，链表的元素：" + linkedList);
    }
}

Running the above code will output the following results:

链表的元素：[Element 3, Element 2, Element 1]
链表的第一个元素：Element 3
删除第一个元素后，链表的元素：[Element 2, Element 1]

As can be seen from the above sample code, by calling the addFirst() method of the LinkedList class, we Elements can be added to the beginning of the linked list. Use the getFirst() method to get the first element of the linked list, and use the removeFirst() method to delete the first element of the linked list.

In summary, the addFirst() method of the LinkedList class is a simple and effective operation in Java to add elements to the beginning of the linked list. It makes it easy to insert new elements and maintain the structure of the linked list. Using the LinkedList class, we can flexibly operate linked lists to meet various needs.

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