LinkedListMap.java

package SetBasicsAndBSTSet;

import java.util.ArrayList;

/**
 * @ Description: 利用链表实现映射
 * @ Date: Created in 21:57 20/07/2018
 * @ Author: Anthony_Duan
 */
public class LinkedListMap<K, V> implements Map<K, V> {

    private class Node {

        public K key;
        public V value;
        public Node next;


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


        public Node(K key, V value) {
            this(key, value, null);
        }

        public Node() {
            this(null, null, null);
        }


        @Override
        public String toString() {
            return key.toString() + ":" + value.toString();
        }
    }


    private Node dummyHead;
    private int size;

    public LinkedListMap() {
        dummyHead = new Node();
        size = 0;
    }


    private Node getNode(K key) {

        Node cur = dummyHead.next;
        while (cur != null) {
            if (cur.key.equals(key)) {
                return cur;
            }
        }
        return null;
    }


    @Override
    public void add(K key, V value) {
        Node node = getNode(key);
        if (node == null) {
            dummyHead.next = new Node(key, value, dummyHead.next);
        } else {
            node.value = value;
        }
    }


    @Override
    public V remove(K key) {

        Node prev = dummyHead;
        while (prev.next != null) {
            if (prev.next.key.equals(key)) {
                break;
            }
            prev = prev.next;
        }

        //这个if判断必须有
        if (prev.next != null) {
            Node delNode = prev.next;
            prev.next = delNode.next;
            delNode.next = null;
            size--;
            return delNode.value;
        }

        return null;
    }

    @Override
    public boolean contains(K key) {
        return getNode(key) != null;
    }

    @Override
    public V get(K key) {
        Node node = getNode(key);
        return node == null ? null : node.value;
    }

    @Override
    public void set(K key, V newValue) {

        Node node = getNode(key);
        if (node == null) {
            throw new IllegalArgumentException(key + " doesn't exist!");
        }
        node.value = newValue;
    }

    @Override
    public int getSize() {
        return size;
    }

    @Override
    public boolean isEmpty() {
        return size == 0;
    }


    public static void main(String[] args) {

        System.out.println("Pride and Prejudice");

        ArrayList<String> words = new ArrayList<>();
        if (FileOperation.readFile("/Users/duanjiaxing/IdeaProjects/Data-Structure/data-structure/src/SetBasicsAndBSTSet/pride-and-prejudice.txt", words)) {
            System.out.println("Total words: " + words.size());

            LinkedListMap<String, Integer> map = new LinkedListMap<>();
            for (String word : words) {
                if (map.contains(word)) {
                    map.set(word, map.get(word) + 1);
                } else {
                    map.add(word, 1);
                }
            }

            System.out.println("Total different words: " + map.getSize());
            System.out.println("Frequency of PRIDE: " + map.get("pride"));
            System.out.println("Frequency of PREJUDICE: " + map.get("prejudice"));
        }

        System.out.println();
    }
}