java开始到熟悉105-107

1，HashMap基本用法

 package list;

 import java.util.HashMap;
 import java.util.Map;

 /**
  * 测试map的基本用法
  * @author acer
  *
  */
 public class Hashmap {
     public static void main(String[] args)
     {
         Map map=new HashMap();
         System.out.println(map.isEmpty());
         map.put("日本汽车", new car("丰田"));
         map.put("德国汽车", new car("奥迪"));
         map.put("日本电器", new camera("canon"));
         map.put("one", new Integer(1));
         System.out.println(map.size());
         car c=(car)map.get("日本汽车");
         System.out.println(c.name);
         System.out.println(map.containsKey("日本汽车"));
         System.out.println(map.containsValue(new car("canon")));
         System.out.println(map.containsValue(new Integer(1)));
         map.remove("日本");
     }
 }
 class car{
     String name;
     public car(String name)
     {
         this.name=name;
     }
 }
 class camera{
     String name;
     public camera(String name)
     {
         this.name=name;
     }
 }

2.自己定义HashMap()(原始版)

 package list;
 /**
  * 实现较为粗糙的HashMap类
  * Map：1，存放键值对2根据键对象找相应的值对象3键值不能重复
  * @author acer
  *
  */
 public class myHashMap {
     arrmap[] arr=new arrmap[100];//此时暂时不考虑数组扩容问题，只实现一些基本的方法
     int size;
     public void put(Object key,Object value)
     {
         arrmap newarr=new arrmap(key,value);
         //解决键值重复的问题
         for(int i=0;i<size;i++)
         {
             if(arr[i].key.equals(key))
             {
                 arr[i].value=value;
                 return;
             }
         }
         arr[size++]=newarr;
     }
     public Object get(Object key)
     {
         for(int i=0;i<size;i++)
         {
             if(arr[i].key.equals(key))
                 return arr[i].value;
         }
         return null;
     }
     public boolean containsKey(Object key)
     {
         for(int i=0;i<size;i++)
         {
             if(arr[i].key.equals(key))
             {
                 return true;
             }
         }
         return false;
     }
     public boolean containsValue(Object value)
     {
         for(int i=0;i<size;i++)
         {
             if(arr[i].value.equals(value))
             {
                 return true;
             }
         }
         return false;
     }
     public static void main(String[] args)
     {
         myHashMap arr=new myHashMap();
         arr.put("日本", new car("丰田"));
         arr.put("德国", new car("奔驰"));
         arr.put("美国", new car("福特"));
         arr.put("日本电器", new camera("canon"));
         car c=(car)arr.get("日本");
         System.out.println(c.name);
         camera d=(camera)arr.get("日本电器");
         System.out.println(d.name);
         System.out.println(arr.containsKey("日本"));
         System.out.println(arr.containsValue(new car("丰田")));
         arr.put("日本", new car("本田"));
         c=(car)arr.get("日本");
         System.out.println(c.name);
     }
 }
  class arrmap
 {
     Object key;
     Object value;
     public arrmap(Object key,Object value)
     {
         this.key=key;
         this.value=value;
     }
 }

3.升级版

 package list;

 import java.util.LinkedList;

 /**
  * 完善粗糙的myhashmap
  * 提高查询效率
  * @author acer
  *
  */
 public class myHashMapUpdate {
     LinkedList[] arr=new LinkedList[999];
     int size;
     public void put(Object key,Object value)
     {
         arrmap arra=new arrmap(key,value);
         int a=key.hashCode()%999;
         if(arr[a]==null)
         {
             LinkedList list=new LinkedList();
             arr[a]=list;
             list.add(arra);
         }
         else
         {
             LinkedList list=arr[a];
             for(int i=0;i<list.size();i++)
             {
                 arrmap arra1=(arrmap)list.get(i);
                 if(arra1.key.equals(key))
                 {
                     arra1.value=value;
                     return;
                 }
             }
             arr[a].add(arra);
         }
     }
     public Object get(Object key)
     {
         int a=key.hashCode()%999;
         if(arr[a]!=null)
         {
             LinkedList list=arr[a];
             for(int i=0;i<list.size();i++)
             {
                 arrmap arra=(arrmap)list.get(i);
                 if(arra.key.equals(key))
                 {
                     return arra.value;
                 }
             }
         }
         return null;
     }
     public static void main(String[] args)
     {
         myHashMapUpdate arr=new myHashMapUpdate();
         arr.put("日本", new car("丰田"));
         arr.put("日本", new car("本田"));
         arr.put("德国", new car("奔驰"));
         arr.put("美国", new car("福特"));
         arr.put("日本电器", new camera("canon"));
         car c=(car)arr.get("日本");
         System.out.println(c.name);
     }
 }