1，HashMap基本用法
1 package list; 2 3 import java.util.HashMap; 4 import java.util.Map; 5 6 /** 7 * 测试map的基本用法 8 * @author acer 9 * 10 */ 11 public class Hashmap { 12 public static void main(String[] args) 13 { 14 Map map=new HashMap(); 15 System.out.println(map.isEmpty()); 16 map.put("日本汽车", new car("丰田")); 17 map.put("德国汽车", new car("奥迪")); 18 map.put("日本电器", new camera("canon")); 19 map.put("one", new Integer(1)); 20 System.out.println(map.size()); 21 car c=(car)map.get("日本汽车"); 22 System.out.println(c.name); 23 System.out.println(map.containsKey("日本汽车")); 24 System.out.println(map.containsValue(new car("canon"))); 25 System.out.println(map.containsValue(new Integer(1))); 26 map.remove("日本"); 27 } 28 } 29 class car{ 30 String name; 31 public car(String name) 32 { 33 this.name=name; 34 } 35 } 36 class camera{ 37 String name; 38 public camera(String name) 39 { 40 this.name=name; 41 } 42 }
2.自己定义HashMap()(原始版)
1 package list; 2 /** 3 * 实现较为粗糙的HashMap类 4 * 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 5 * @author acer 6 * 7 */ 8 public class myHashMap { 9 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 10 int size; 11 public void put(Object key,Object value) 12 { 13 arrmap newarr=new arrmap(key,value); 14 //解决键值重复的问题 15 for(int i=0;i<size;i++) 16 { 17 if(arr[i].key.equals(key)) 18 { 19 arr[i].value=value; 20 return; 21 } 22 } 23 arr[size++]=newarr; 24 } 25 public Object get(Object key) 26 { 27 for(int i=0;i<size;i++) 28 { 29 if(arr[i].key.equals(key)) 30 return arr[i].value; 31 } 32 return null; 33 } 34 public boolean containsKey(Object key) 35 { 36 for(int i=0;i<size;i++) 37 { 38 if(arr[i].key.equals(key)) 39 { 40 return true; 41 } 42 } 43 return false; 44 } 45 public boolean containsValue(Object value) 46 { 47 for(int i=0;i<size;i++) 48 { 49 if(arr[i].value.equals(value)) 50 { 51 return true; 52 } 53 } 54 return false; 55 } 56 public static void main(String[] args) 57 { 58 myHashMap arr=new myHashMap(); 59 arr.put("日本", new car("丰田")); 60 arr.put("德国", new car("奔驰")); 61 arr.put("美国", new car("福特")); 62 arr.put("日本电器", new camera("canon")); 63 car c=(car)arr.get("日本"); 64 System.out.println(c.name); 65 camera d=(camera)arr.get("日本电器"); 66 System.out.println(d.name); 67 System.out.println(arr.containsKey("日本")); 68 System.out.println(arr.containsValue(new car("丰田"))); 69 arr.put("日本", new car("本田")); 70 c=(car)arr.get("日本"); 71 System.out.println(c.name); 72 } 73 } 74 class arrmap 75 { 76 Object key; 77 Object value; 78 public arrmap(Object key,Object value) 79 { 80 this.key=key; 81 this.value=value; 82 } 83 }
3.升级版
1 package list; 2 3 import java.util.LinkedList; 4 5 /** 6 * 完善粗糙的myhashmap 7 * 提高查询效率 8 * @author acer 9 * 10 */ 11 public class myHashMapUpdate { 12 LinkedList[] arr=new LinkedList[999]; 13 int size; 14 public void put(Object key,Object value) 15 { 16 arrmap arra=new arrmap(key,value); 17 int a=key.hashCode()%999; 18 if(arr[a]==null) 19 { 20 LinkedList list=new LinkedList(); 21 arr[a]=list; 22 list.add(arra); 23 } 24 else 25 { 26 LinkedList list=arr[a]; 27 for(int i=0;i<list.size();i++) 28 { 29 arrmap arra1=(arrmap)list.get(i); 30 if(arra1.key.equals(key)) 31 { 32 arra1.value=value; 33 return; 34 } 35 } 36 arr[a].add(arra); 37 } 38 } 39 public Object get(Object key) 40 { 41 int a=key.hashCode()%999; 42 if(arr[a]!=null) 43 { 44 LinkedList list=arr[a]; 45 for(int i=0;i<list.size();i++) 46 { 47 arrmap arra=(arrmap)list.get(i); 48 if(arra.key.equals(key)) 49 { 50 return arra.value; 51 } 52 } 53 } 54 return null; 55 } 56 public static void main(String[] args) 57 { 58 myHashMapUpdate arr=new myHashMapUpdate(); 59 arr.put("日本", new car("丰田")); 60 arr.put("日本", new car("本田")); 61 arr.put("德国", new car("奔驰")); 62 arr.put("美国", new car("福特")); 63 arr.put("日本电器", new camera("canon")); 64 car c=(car)arr.get("日本"); 65 System.out.println(c.name); 66 } 67 }