java集合之间的关系及实现细节——Set与Map

 1 package com.ngu4k.test.collection;
 2 
 3 import java.io.Serializable;
 4 import java.util.Map.Entry;
 5 
 6 public class SimpleEntry<K,V> implements Entry<K,V>,Serializable{
 7     private static final long serialVersionUID = -4352059623055803486L;
 8     private final K key;
 9     private V value;
10     //定义两个如下构造器
11     public SimpleEntry(K key,V value)
12     {
13         this.key = key;
14         this.value = value;
15     }
16     
17     public SimpleEntry(Entry<? extends K,? extends V> entry)
18     {
19         this.key = entry.getKey();
20         this.value = entry.getValue();
21     }
22     //获取key
23     public K getKey() 
24     {
25         return key;
26     }
27     //获取value
28     public V getValue() 
29     {
30         return value;
31     }
32     //改变该key-value对的value值
33     public V setValue(V value) 
34     {
35         V oldValue = this.value;
36         this.value = value;
37         return oldValue;
38     }
39     //根据key比较两个对象是否相等
40     public boolean equals(Object o)
41     {
42         if(o == this){
43             return true;
44         }
45         if(o.getClass() == SimpleEntry.class){
46             SimpleEntry se = (SimpleEntry)o;
47             return se.getKey().equals(getKey());
48         }
49         return false;
50     }
51     //根据key获得hashCode的值
52     public int hashCode(){
53         return key == null ? 0 : key.hashCode();
54     }
55     
56     public String toString(){
57         return key + "=" + value;
58     }
59 }

  1 package com.ngu4k.test.collection.map;
  2 
  3 import java.util.HashSet;
  4 import java.util.Iterator;
  5 import java.util.Map;
  6 
  7 import com.ngu4k.test.collection.SimpleEntry;
  8 
  9 /**
 10  * Set到Map的简单实现
 11  * @author ikouer
 12  * @param <K>
 13  * @param <V>
 14  */
 15 public class Set2Map<K,V> extends HashSet<SimpleEntry<K,V>>{
 16 
 17     private static final long serialVersionUID = 1596710712757978024L;
 18     
 19     //清空Set2Map中key-value对
 20     public void clear()
 21     {
 22         super.clear();
 23     }
 24     //查看是否包含指定的key
 25     public boolean containsKey(K key)
 26     {
 27         return super.contains(new SimpleEntry<K, V>(key,null));
 28     }
 29     //查看是否包含指定的value
 30     public boolean containsValue(V value)
 31     {
 32         for(SimpleEntry<K,V> se : this)
 33         {
 34             if(se.getValue().equals(value))
 35             {
 36                 return true;
 37             }
 38         }
 39         return false;
 40     }
 41     //根据指定的key获取对应的value
 42     public V get(K key)
 43     {
 44         for(SimpleEntry<K,V> se : this)
 45         {
 46             if(se.getKey().equals(key)){
 47                 return se.getValue();
 48             }
 49         }
 50         return null;
 51     }
 52     //把指定的key-value添加到集合中
 53     public V put(K key,V value)
 54     {
 55         this.add(new SimpleEntry<K,V>(key,value));
 56         return value;
 57     }
 58     //把一个Map集合添加到Set2Map集合中
 59     public void putAll(Map<? extends K,? extends V> om)
 60     {
 61         for(K key : om.keySet())
 62         {
 63             this.add(new SimpleEntry<K,V>(key,om.get(key)));
 64         }
 65     }
 66     //根据指定的key移除对应的key-value
 67     public V remove(K key)
 68     {
 69         for(Iterator<SimpleEntry<K,V>> it = this.iterator(); it.hasNext();){
 70             SimpleEntry<K,V> se = it.next();
 71             if(se.getKey().equals(key))
 72             {
 73                 V rv = se.getValue();
 74                 it.remove();
 75                 return rv;
 76             }
 77         }
 78         return null;
 79     }
 80     //获取集合大小
 81     public int size(){
 82         return super.size();
 83     }
 84     
 85     public static void main(String[] args) {
 86         Set2Map<String,Integer> smap = new Set2Map<String,Integer>();
 87         //将key-value放入集合
 88         smap.put("语文", 88);
 89         smap.put("数学", 99);
 90         smap.put("英语", 102);
 91         System.out.println(smap);
 92         System.out.println(smap.size());
 93         //执行移除对称key的entry
 94         smap.remove("数学");
 95         System.out.println("删除key为\"数学\"的Entry之后:"+smap);
 96         //获取key为语文的value值
 97         System.out.println("key为\"语文\"的value值："+smap.get("语文"));
 98         //判断是否包含key
 99         System.out.println("是否包含key为\"英语\"的entry:"+smap.containsKey("英语"));
100         //判断是否包含value
101         System.out.println("是否包含value为102:"+smap.containsValue(102));
102         //执行clear方法
103         smap.clear();
104         System.out.println("执行完clear()方法之后的集合："+smap);
105         
106     }
107 }