Java基础

package ycw;

class ListNode{ //注意这里不能有public
    int val;
    ListNode next;
    ListNode(){}
    ListNode(int val){
        this.val = val;
    }
}
public class Test {
    public static void main(String[] args){
        Test a = new Test();
        ListNode head = new ListNode(1);
        head.next = new ListNode(2);
        a.change(head.next); //把head.next的地址传递给了change.
        System.out.println(head.next.val); //还是等于2.
    }

    public void change(ListNode head){
        head.next.val = 3;
    }
}