双向循环链表返回元素x第一次出现在双向循环链表中的位置号Java代码

以下是返回元素x第一次出现的位置号的Java代码示例：

public class Node {
    int data;
    Node prev;
    Node next;
    
    public Node(int data) {
        this.data = data;
        this.prev = null;
        this.next = null;
    }
}

public class DoublyLinkedList {
    Node head;
    
    public void addNode(int data) {
        Node newNode = new Node(data);
        
        if (head == null) {
            head = newNode;
            head.next = head;
            head.prev = head;
        } else {
            Node last = head.prev;
            
            last.next = newNode;
            newNode.prev = last;
            
            newNode.next = head;
            head.prev = newNode;
        }
    }
    
    public int findFirstOccurrence(int x) {
        if (head == null) {
            return -1; // List is empty
        }
        
        Node current = head;
        int position = 0;
        
        do {
            if (current.data == x) {
                return position;
            }
            
            current = current.next;
            position++;
        } while (current != head);
        
        return -1; // Element not found
    }
}

// Usage example
public class Main {
    public static void main(String[] args) {
        DoublyLinkedList list = new DoublyLinkedList();
        
        list.addNode(1);
        list.addNode(2);
        list.addNode(3);
        list.addNode(4);
        list.addNode(5);
        
        int x = 3;
        int position = list.findFirstOccurrence(x);
        
        if (position != -1) {
            System.out.println("Element " + x + " found at position " + position);
        } else {
            System.out.println("Element " + x + " not found in the list");
        }
    }
}

这段代码定义了一个双向循环链表的实现，并提供了一个方法 `findFirstOccurrence`，该方法用于返回元素 x 第一次出现在双向循环链表中的位置号。你可以根据需要进行修改和扩展。