/**
 * @desc: 基於單鏈表實現有序Map
 *        有序Map，主要是在插入元素時，保證佇列有序即可，所以key需要實現Comparable介面。
 * @author: 毛會懂
 * @create: 2020-12-30 13:31:00
 **/
public class MyOrderMap<K extends Comparable<K>,V> implements Iterable<K>{
    private Node head;
    private Integer count;

    public MyOrderMap() {
        
 
this.head = new Node(null,null,null);
        count = 0;
    }

    //插入元素時，保證有序
    public void put(K key,V value){
        Node curNode = head;
        Node pre = null;
        Node newNode = new Node(key,value,null);
        while (curNode.next != null){
            pre = curNode;
            curNode 
 
= curNode.next;
            if(curNode.key.compareTo(key) == 0){
                curNode.value = value;
                return;
            }else if(curNode.key.compareTo(key) > 0){
                pre.next = newNode;
                newNode.next = curNode;
                count++;
                
 
return;
            }
        }
        //已經遍歷到末尾，則直接新增
        curNode.next = newNode;
        count++;
    }

    //獲取元素
    public V get(K key){
        Node temp = head;
        while (temp.next != null){
            temp = temp.next;
            if(temp.key.equals(key)){
                return temp.value;
            }
        }
        return null;
    }

    //刪除元素
    public V del(K key){
        if(isEmpty()){
            return null;
        }
        Node node = head;
        Node pre = null;
        while (node.next != null){
            //上一個節點
            pre = node;
            //當前節點
            node = node.next;
            if(node.key.equals(key)){
                pre.next = node.next;
                return node.value;
            }
        }
        return null;
    }

    public Boolean isEmpty(){
        return count == 0;
    }

    //
    public Integer size(){
        return count;
    }

    @Override
    public Iterator<K> iterator() {
        return new MyIterator();
    }

    public class MyIterator implements Iterator<K>{
        private Node node;

        public MyIterator(){
            node = head;
        }

        @Override
        public boolean hasNext() {
            return node.next != null;
        }

        @Override
        public K next() {
            node = node.next;
            return node.key;
        }
    }

    private class Node{
        private K key;
        private V value;
        private Node next;

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

測試（Student的定義見上一篇文章）：

 MyOrderMap<String,String> map = new MyOrderMap();
    map.put("abc","abc");
    map.put("bcd","dddd");
    System.out.println("取元素：" + map.get("bcd"));
    System.out.println("取元素：" + map.get("abcd")); //沒有這個key，所以取出來是null
    System.out.println("元素的個數：" + map.size());
    System.out.println("元素是否為空：" + map.isEmpty());

    System.out.println("--------以下演示key為Student物件的使用----------");
    Student[] stus = {
            new Student("b", 11),
            new Student("a", 10),
            new Student("c", 12),
            new Student("b", 111),
            new Student("a", 111),
            new Student("c", 4)};
    MyOrderMap<Student,Integer> stuMap = new MyOrderMap<>();
    stuMap.put(stus[0],11);
    stuMap.put(stus[1],111);
    stuMap.put(stus[2],11);
    stuMap.put(stus[3],122);
    stuMap.put(stus[4],12); //這裡根據年齡判斷的key是否相同，所以stus[3]和stus[4] key相同
    stuMap.put(stus[5],11);
    Integer value = stuMap.get(stus[3]);
    System.out.println(value);
    System.out.println("遍歷學生map");
    Iterator<Student> iterator = stuMap.iterator();
    while (iterator.hasNext()){
        Student next = iterator.next();
        System.out.println("姓名：" + next.getName() + "  年齡：" + next.getAge() + " 值：" + stuMap.get(next));
    }
    System.out.println("-----刪除元素-----");
    Integer del = stuMap.del(stus[5]);
    System.out.println("刪除的value=" + del);
}