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MAP of multiple datatypes

Posted on 2009-04-03

Java

1 solution

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Last Modified: 2013-11-23

Hi,

I'm new to JAVA and I'm trying to achieve something that the JAVA Map seems to be the solution for, but I'm hitting a wall. Basically I want to have a MAP of values BUT with different data types. That doesn't work (maybe I'm doing something wrong) as it asks me to declare the Map parameterized.

Below is a sample snippet of what I want to do.

Note: I know I can use the Memento pattern to achieve this, but I'm wondering if this is at all possible.

public class MyClass{
 
protected Map instance;
 
  public void setName( String sName ){
    this.instance.put("sName",sName);
  }
  public void setDate(Date date){
    this.instance.put("date", date)
  }
  public Map getInstanceState(){
    return Collections.unmodifiableMap(this.instance);
  }
}

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Question by:lostlinkpr

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3 Comments

LVL 25

Accepted Solution

by:InteractiveMind

InteractiveMind earned 500 total points

ID: 240664562009-04-04

Why not just use a HashMap? (Attached is an example)

import java.util.HashMap;
 
public class Ex
{
   public Ex()
   {
      HashMap hm=new HashMap();
      hm.put("sn","InteractiveMind");
      hm.put("size",new Integer(200));
      
   }
   
   public static void main(String[]a)
   {new Ex();}
}

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LVL 1

Author Comment

by:lostlinkpr

ID: 240678262009-04-04

Thank you, that works! The compiler (Eclipse) still throws a warning saying the HashMap should be parameterized but it works well.

final snippet:

protected HashMap inst = new HashMap();
 
    /*
     * Get the state of the object properties at a specific moment
     * 
     * @return unmodifiable SortedMap (memento of object)
     */
    public Map getMemento(){
    	return Collections.unmodifiableSortedMap( new TreeMap(this.inst) );
    }

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LVL 25

Expert Comment

by:InteractiveMind

ID: 240679772009-04-04

Yes, from Java 5 onwards, parametrisation is available (and thus recommended by the compiler), but it's not necessary, just good coding practice (when viable).

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