简易java链表（含构造、toString、测试用例）

class ListNode {
    int val;
    ListNode next;
    ListNode(int x) {
        val = x;
    }
    ListNode(int[] x) {//保证输入的数组至少有1个元素
        val = x[0];
        ListNode n = this;
        for (int i = 1; i < x.length; i++) {
            //给next开空间，赋值
            n.next = new ListNode(x[i]);
            //下一个
            n = n.next;
        }
    }

    @Override
    public String toString() {
        String s = "" + this.val;
        if (this.next != null) {
            ListNode n = this.next;
            while (true) {
                s += n.val;
                if (n.next == null) break;//没下一个了
                //有下一个
                n = n.next;
            }
        }
        return s;
    }

    public static void deleteNode(ListNode node) {
        node.val = node.next.val;
        node.next = node.next.next;
    }
}

测试方法：

public static void main(String[] args) {
        //4519
        ListNode n = new ListNode(4);
        //保存起点
        ListNode start = n;

//        n=n.next;//此处不起作用，因为n.next为空，所以赋值无效！
        //所以先让next有值，再让n=n.next才生效！
        //给next赋值
        n.next = new ListNode(5);
        //让n=n.next
        n = n.next;//n现在代表5
        //以下重复
        n.next = new ListNode(1);
        n = n.next;//1
        n.next = new ListNode(9);
        n = n.next;//9
        n.next = null;//9为最后一个，next=null


        System.out.println(start.val + " " + start.next.val 
        + " " + start.next.next.val + " " + start.next.next.next.val);
        System.out.println(start);
        System.out.println("---------------------------------");

        //4519
        //新写的构造
        ListNode nn = new ListNode(new int[]{4, 5, 1, 9});
        //保存起点
        ListNode startn = nn;
        System.out.println(startn);
    }