我需要创建密钥作为整数一个HashMap,它应该保持不同的数据类型的多个值。例如,如果关键是MSG ID和值
那么如何不同数据类型的值存储与单个键进入HashMap的?
如果你没有自己的数据类,那么你可以设计自己的地图如下
Map<Integer, Object> map=new HashMap<Integer, Object>();
这里不要忘记,而从地图检索值用“的instanceof”操作符。
如果你有自己的数据类,那么,那么你可以设计自己的地图如下
Map<Integer, YourClassName> map=new HashMap<Integer, YourClassName>();
import java.util.Date;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
public class HashMapTest {
public static void main(String[] args) {
Map<Integer,Demo> map=new HashMap<Integer, Demo>();
Demo d1= new Demo(1,"hi",new Date(),1,1);
Demo d2= new Demo(2,"this",new Date(),2,1);
Demo d3= new Demo(3,"is",new Date(),3,1);
Demo d4= new Demo(4,"mytest",new Date(),4,1);
//adding values to map
map.put(d1.getKey(), d1);
map.put(d2.getKey(), d2);
map.put(d3.getKey(), d3);
map.put(d4.getKey(), d4);
//retrieving values from map
Set<Integer> keySet= map.keySet();
for(int i:keySet){
System.out.println(map.get(i));
}
//searching key on map
System.out.println(map.containsKey(d1.getKey()));
//searching value on map
System.out.println(map.containsValue(d1));
}
}
class Demo{
private int key;
private String message;
private Date time;
private int count;
private int version;
public Demo(int key,String message, Date time, int count, int version){
this.key=key;
this.message = message;
this.time = time;
this.count = count;
this.version = version;
}
public String getMessage() {
return message;
}
public Date getTime() {
return time;
}
public int getCount() {
return count;
}
public int getVersion() {
return version;
}
public int getKey() {
return key;
}
@Override
public String toString() {
return "Demo [message=" + message + ", time=" + time
+ ", count=" + count + ", version=" + version + "]";
}
}
你有一些变量是不同类型的像Java语言:
message of type string
timestamp of type time
count of type integer
version of type integer
如果您使用HashMap,如:
HashMap<String,Object> yourHash = new HashMap<String,Object>();
yourHash.put("message","message");
yourHash.put("timestamp",timestamp);
yourHash.put("count ",count);
yourHash.put("version ",version);
如果你想使用yourHash:
for(String key : yourHash.keySet()){
String message = (String) yourHash.get(key);
Datetime timestamp= (Datetime) yourHash.get(key);
int timestamp= (int) yourHash.get(key);
}
定义一个类来第一存储数据
public class YourDataClass {
private String messageType;
private Timestamp timestamp;
private int count;
private int version;
// your get/setters
...........
}
然后初始化您的地图:
Map<Integer, YourDataClass> map = new HashMap<Integer, YourDataClass>();
创建一个对象持有以下属性以适当的名称。
并以此作为你的映射中的值。
也可以考虑重写的equals()和hashCode()方法,因此,如果你不想使用对象平等的比较(例如将值插入到你的地图时)。
不要简单地像下面....
HashMap<String,Object> yourHash = new HashMap<String,Object>();
yourHash.put(yourKey+"message","message");
yourHash.put(yourKey+"timestamp",timestamp);
yourHash.put(yourKey+"count ",count);
yourHash.put(yourKey+"version ",version);
强制转换的价值,同时找回。对于例如:
int count = Integer.parseInt(yourHash.get(yourKey+"count"));
//or
int count = Integer.valueOf(yourHash.get(yourKey+"count"));
//or
int count = (Integer)yourHash.get(yourKey+"count"); //or (int)