自定义线性结构-Map

**
 * @desc: 基于单链表实现Map结构
 * 实现Iterable接口，方便遍历Map
 * @author: 毛会懂
 * @create: 2020-12-30 13:31:00
 **/
public class MyMap<K,V> implements Iterable<K>{
    private Node head;
    private Integer count;

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

    //插入元素
    public void put(K key,V value){
        Node newNode = new Node(key,value,null);
        Node temp = head;
        while (temp.next != null){
            temp = temp.next;
            if(temp.key.equals(key)){
                temp.value = value;
                return;
            }
        }
        temp.next = newNode;
        count++;
    }

    //获取元素
    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;
    }

    //删除元素
    public V del(K key){
        if(isEmpty()){
            return null;
        }
        Node node = head;
        Node pre = null;
        while (node.next != null){
            //上一个节点
            pre = node;
            //当前节点
            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;
        }
    }
}

 //map的key可以是对象，这里实现了Comparable接口，为下一篇有序Map做铺垫。

public class Student implements Comparable<Student>{
    private String name;
    private Integer age; //为了方便，假设age不能为空吧

    public Student(String name, Integer age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }


    @Override
    public boolean equals(Object obj) {
        if(this == obj){
            return true;
        }
        if(obj == null){
            return false;
        }

        if(obj instanceof Student){
            Student temp = (Student) obj;
            //这里就假设age不能为空吧
            if(temp.age.equals(this.age)){
                return true;
            }
        }
        return false;
    }

    @Override
    public int hashCode() {
        return age.hashCode();
    }

    @Override
    public int compareTo(Student o) {
        return this.getAge() - o.age;
    }
}

测试：

//非有序的map
public static void main2(String[] args) {
    MyMap<String,String> map = new MyMap();
    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"));
    System.out.println("元素的个数：" + map.size());
    System.out.println("元素是否为空：" + map.isEmpty());

    System.out.println("--------以下演示key为Student对象的使用----------");
    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)};
    MyMap<Student,Integer> stuMap = new MyMap<>();
    stuMap.put(stus[0],11);
    stuMap.put(stus[1],111);
    stuMap.put(stus[2],11);
    stuMap.put(stus[3],122);
    stuMap.put(stus[4],11); //这里根据年龄判断的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("遍历学生map");
    Iterator<Student> iterator = stuMap.iterator();
    while (iterator.hasNext()){
        Student next = iterator.next();
        System.out.println("姓名：" + next.getName() + "  年龄：" + next.getAge() + " 值：" + stuMap.get(next));
    }
    System.out.println("-----删除元素-----");
    Integer del = stuMap.del(stus[5]);
    System.out.println("删除的value=" + del);
}