I need to create a hashmap with key as integer and it should hold multiple values of different data types. For example if the key is msg id and the values are
Then how to store the values of different data type with a single key into the hashmap?
If you don't have Your own Data Class, then you can design your map as follows
Map<Integer, Object> map=new HashMap<Integer, Object>();Here don't forget to use "instanceof" operator while retrieving the values from MAP.
If you have your own Data class then then you can design your map as follows
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 + "]";
}
}
You have some variables that are different types in Java language like that:
message of type string
timestamp of type time
count of type integer
version of type integer
If you use a HashMap like:
HashMap<String,Object> yourHash = new HashMap<String,Object>();
yourHash.put("message","message");
yourHash.put("timestamp",timestamp);
yourHash.put("count ",count);
yourHash.put("version ",version);
If you want to use the yourHash:
for(String key : yourHash.keySet()){
String message = (String) yourHash.get(key);
Datetime timestamp= (Datetime) yourHash.get(key);
int timestamp= (int) yourHash.get(key);
}
Define a class to store your data first
public class YourDataClass {
private String messageType;
private Timestamp timestamp;
private int count;
private int version;
// your get/setters
...........
}
And then initialize your map:
Map<Integer, YourDataClass> map = new HashMap<Integer, YourDataClass>();
Create an object holding following properties with an appropriate name.
and use this as a value in your map.
Also consider overriding the equals() and hashCode() method accordingly if you do not want object equality to be used for comparison (e.g. when inserting values into your map).
equals() and hashCode() are not important, as his keys will be Integer.
equals()), you need to explain why this is important. Merely highlighting best practice will tend to bloat answers unnecessarily.Do simply like below....
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);
typecast the value while getting back. For ex:
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)
Map<Integer, YourClass>