数据结构-链表实现--待更新

实体类：ListNode

public class ListNode {
    int val;
    ListNode next;
    ListNode() {}
    ListNode(int val) { this.val = val; }
    ListNode(int val, ListNode next) { this.val = val; this.next = next; }

}

 链表实现：插入和打印 LinkedList 

public class LinkedList {
    ListNode head;

//     插入节点到链表尾部
    public void insert(int val) {
        ListNode newNode = new ListNode(val);

        if (head == null) {
            // 如果链表为空，新节点成为头节点
            head = newNode;
        } else {
            // 否则，遍历到链表尾部并插入新节点
            ListNode current = head;
            while (current.next != null) {
                current = current.next;
            }
            current.next = newNode;
        }
    }

//     打印链表
    public void printList() {
        ListNode current = head;
        while (current != null) {
            System.out.print(current.val + " -> ");
            current = current.next;
        }
        System.out.println("null");
    }

}

测试类：

public class LibraryTest extends TestCase {

    @Test
    public void testAddNode() {

        LinkedList linkedList = new LinkedList();
        linkedList.insert(2);
        linkedList.insert(1);
        linkedList.printList();

    }
}

问题：

传入参数1时

此时的head结构是[2,null]

current.next=newNode更新后，为什么head也更新了？

从代码：ListNode current = head;

这代表着current和head指向同一对象，current发生改变，head也更新