用Java实现反转链表起⽹络

反转链表是一个常见的面试题，以下是用Java实现反转链表的代码：

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

class ReverseLinkedList {
    Node head;
    
    public ReverseLinkedList() {
        head = null;
    }
    
    public void insert(int val) {
        if (head == null) {
            head = new Node(val);
            return;
        }
        Node curr = head;
        while (curr.next != null) {
            curr = curr.next;
        }
        curr.next = new Node(val);
    }
    
    public void reverse() {
        Node prev = null;
        Node curr = head;
        Node next = null;
        while (curr != null) {
            next = curr.next;
            curr.next = prev;
            prev = curr;
            curr = next;
        }
        head = prev;
    }
    
    public void printList() {
        Node curr = head;
        while (curr != null) {
            System.out.print(curr.val + " ");
            curr = curr.next;
        }
        System.out.println();
    }
}

这里定义了一个Node类和ReverseLinkedList类，Node类表示链表中的节点，ReverseLinkedList类表示链表。insert方法用于插入节点，reverse方法用于反转链表，printList方法用于打印链表。reverse方法里使用了三个指针prev、curr、next，分别表示前一个节点、当前节点和下一个节点，通过改变节点之间的链接关系，实现了反转链表的功能。