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Java帝国之实现无/有序符号表

​ 符号表最主要的目的是将一个键和一个值联系起来，通过查找键的方式找到对应的值。其中键具有唯一性。

如座位号、图书编号等，具有一一对应的关系。

1. 无序符号表

public class SymbolTable<Key, Value> {

    private Node head; // 首节点
    private int N;     // 长度

    public SymbolTable(){
        head = new Node<>();
    }

    private class Node<Key, Value>{
        public Key key;     // 键
        public Value value; // 值
        public Node next;   // 下指针

        public Node(){}
        public Node(Key key, Value value){
            this.key = key;
            this.value = value;
        }
    }

    /**
     * 根据键，返回对应值
     * @param key   键
     * @return      值
     */
    public Value get(Key key){
        Node tmp = this.head;
        while (tmp.next != null && !tmp.next.key.equals(key))
            tmp = tmp.next;
        return tmp.next == null ? null : (Value)tmp.next.value;
    }

    /**
     * 向符号表中插入一个键值对
     * 注意：键具有唯一性！！！ 如果插入的键key已存在则覆盖值value
     * @param key   键
     * @param val   值
     */
    public void put(Key key, Value val){
        Node tmp = this.head;
        while(tmp.next != null && !tmp.next.key.equals(key)){
            tmp = tmp.next;
        }
        if(tmp.next != null && tmp.next.key.equals(key)){
            tmp.next.value = val;
            return;
        }
        Node<Key, Value> newNode = new Node<>(key, val);
        newNode.next = tmp.next;
        tmp.next = newNode;
        this.N++;
    }

    /**
     * 删除指定键的键值对 不存在不删除
     * @param key
     */
    public void delete(Key key){
        Node tmp = this.head;
        while (tmp.next != null && !tmp.next.key.equals(key))
            tmp = tmp.next;
        if(tmp.next == null)
            return;
        if(tmp.next.next != null)
            tmp.next = tmp.next.next;
        else tmp.next = null;
        this.N--;
    }

    public int size(){
        return this.N;
    }

    public boolean isEmpty(){
        return this.N == 0;
    }

    @Override
    public String toString() {
        StringBuilder stringBuilder = new StringBuilder();
        Node tmp = this.head;
        while (tmp.next != null){
            tmp = tmp.next;
            stringBuilder.append("key: ").append(tmp.key).append(" value: ").append(tmp.value).append("\n");
        }
        return stringBuilder.toString();
    }
}

测试：

public class SymbolTableTest {
    public static void main(String[] args) {
        //创建符号表对象
        SymbolTable<Integer, String> symbolTable = new SymbolTable<>();

        //测试put方法（插入,替换）
        symbolTable.put(1,"乔峰");
        symbolTable.put(2,"虚竹");
        symbolTable.put(3,"段誉");
        System.out.println("插入完毕后，元素的个数为:" + symbolTable.size());
        System.out.println(symbolTable);

        symbolTable.put(2, "慕容复");
        System.out.println("替换完毕后的元素的个数为:" + symbolTable.size());
        System.out.println(symbolTable);

        //测试get方法
        System.out.println("替换完毕后，键2对应的值为:" + symbolTable.get(0));
        System.out.println(symbolTable);

        //测试删除方法
        symbolTable.delete(2);
        System.out.println("删除完毕后，元素的个数:" + symbolTable.size());
        System.out.println(symbolTable);
    }
}

2. 有序符号表

package com.jsoft.work;

public class OrderSymbolTable<Key, Value> {

    private Node head;  // 首节点
    private int N;      // 长度

    public OrderSymbolTable(){
        this.head = new Node<>();
    }

    private class Node<Key, Value>{
        public Key key;        // 键
        public Value value;    // 值
        public Node next;      // 下指针

        public Node(){}
        public Node(Key key, Value value){
            this.key = key;
            this.value = value;
        }
    }

    /**
     * 根据键，返回对应值
     * @param key   键
     * @return      值
     */
    public Value get(Key key){
        Node tmp = this.head;
        while (tmp.next != null && !tmp.next.key.equals(key))
            tmp = tmp.next;
        return tmp.next == null ? null : (Value) tmp.next.value;
    }

    /**
     * 向符号表中按照键的升序插入一个键值对
     * 注意：键具有唯一性！！！ 如果插入的键key已存在则覆盖值value
     * @param key   键
     * @param val   值
     */
    public void put(Key key, Value val){
        Node tmp = this.head;
        while (tmp.next != null && String.valueOf(tmp.next.key).compareTo(String.valueOf(key)) < 0)
            tmp = tmp.next;
        if(tmp.next != null && tmp.next.key.equals(key)){
            tmp.next.value = val;
            return;
        }
        Node<Key, Value> newNode = new Node<>(key, val);
        newNode.next = tmp.next;
        tmp.next = newNode;
        this.N++;
    }

    /**
     * 删除指定键的键值对 不存在不删除
     * @param key
     */
    public void delete(Key key){
        Node tmp = this.head;
        while (tmp.next != null && !tmp.next.key.equals(key))
            tmp = tmp.next;
        if(tmp.next == null)
            return;
        if(tmp.next.next != null)
            tmp.next = tmp.next.next;
        else tmp.next = null;
        this.N--;
    }

    public int getN() {
        return this.N;
    }

    public boolean isEmpty(){
        return this.N == 0;
    }

    @Override
    public String toString() {
        StringBuilder stringBuilder = new StringBuilder();
        Node tmp = this.head;
        while (tmp.next != null){
            tmp = tmp.next;
            stringBuilder.append("key: ").append(tmp.key).append(" value: ").append(tmp.value).append("\n");
        }
        return stringBuilder.toString();
    }
}

测试：

public class OrderSymbolTableTest {
    public static void main(String[] args) {
        //创建有序符号表对象
        OrderSymbolTable<Integer, String> table = new OrderSymbolTable<>();
        table.put(1,"张三");
        table.put(2,"李四");
        table.put(4,"赵六");
        table.put(7,"田七");
        table.put(3,"王五");
        System.out.println(table);
    }
}

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