关于hashmap实现的问题[关闭]

Question

我想实现一个hashmap，但是当我测试时，直接运行和调试运行的结果不一致

下面是我的代码

public class HashMap {

    //test
    public static void main(String[] args) {
        var map = new HashMap();
        map.put("c1", "1");
        map.put("w1", "2");
        map.put("m1", "3");
        System.out.println(map.get("c1"));
        System.out.println(map.get("w1"));
        System.out.println(map.get("m1"));
    }
    ListNode[] map = new ListNode[10];

    int size;

    public void put(String key, String value) {
        if (size >= map.length * 0.75f) {
            System.out.println("Capacity expansion required");
        }
        int index = Math.abs(key.hashCode() % map.length);
        ListNode node = map[index];
        if (node == null) {
            node = new ListNode();
            node.head = new Node(key, value, null);
            map[index] = node;
        } else {
            node.addNode(key, value);
        }
        size++;
    }

    public String get(String key) {
        int index = Math.abs(key.hashCode() % map.length);
        ListNode node = map[index];
        if (node == null) {
            return null;
        }
        return node.getValue(key);
    }

    static class Node {
        String key;
        String value;
        Node next;

        public Node(String key, String value, Node next) {
            this.key = key;
            this.value = value;
            this.next = next;
        }
    }

    /**
     * Single linked list container
     */
    static class ListNode {
        Node head;
        Node tail;

        public void addNode(String key, String value) {
            if (head == null) return;
            Node node = new Node(key, value, null);
            //only one
            if (tail == null) {
                if (key.equals(head.key))
                    head.value = value;
                else {
                    head.next = node;
                    tail = node;
                }
            } else {
                if (key.equals(tail.key)) {
                    tail.value = value;
                } else {
                    tail.next = node;
                    tail = node;
                }
            }
        }

        public String getValue(String key) {
            if (head == null) return null;
            if (head.next == null) {
                return head.value;
            } else {
                do {
                    if (key.equals(head.key)) {
                        return head.value;
                    }
                    head = head.next;
                } while (head.next != null);
            }
            return null;
        }
    }
}

这是我的直接运行时的结果

1
2
null

当我在没有断点的情况下调试和运行时，结果同上。但当我踏过它，结果如下

1
2
3

谁能告诉我为什么？？？

Answer 1

您应该在此处处理HashMap的最后一个元素：

do {
    if (key.equals(head.key)) {
        return head.value;
    }
    head = head.next;
} while (head.next != null);

因为头。next在从ListNode获取最后一个元素时没有值，它不能返回m1的值。