Java: create a list of HashMaps

Question

I tried to create a list of maps. In the following code, I'm expecting to get

[{start=1,text=ye}, {start=2,text=no}]

however, I only got

[{start=2,text=no}, {start=2,text=no}]

How to avoid overriding the first map? Here is my code:

HashMap mMap = new HashMap();
ArrayList list = new ArrayList();
list.add(new HashMap());
mMap.put("start",1);
mMap.put("text","yes");
list.add(mMap); 
mMap.put("start",2);
mMap.put("text","no");
list.add(mMap); 
System.out.println("Final result: " + list );

thanks!

==========================

As a learner of Java who came from a procedure language background (SAS), I spent quite a few hours learning and experimenting ArrayList, LinkedList, Map, LinkedMap, etc--- I coldn't get it to work. And I don't understand why with my limited knowledge. Now, these following answers are all excellent! They explained very important data structure in Java, at least for me.

THANK YOU ALL!!!!

Answer 1

Something which is maybe also worth mention it, is that you should define the type of the elements you use in the List, for the HashMap its not possible because you are mixing Integers and Strings.

And another thing is that you should use the List interface as type, so you are able to change the implementation (ArrayList or whatever) in the future.

Here the corrected code:

Map mMap = new HashMap();
List<Map> list = new ArrayList();

Answer 2

You need to create a new HashMap for every entry, instead of reusing the existing one. This would work:

HashMap mMap = new HashMap();
mMap.put("start",1);
mMap.put("text","yes");
list.add(mMap); 
mMap = new HashMap(); // create a new one!
mMap.put("start",2);
mMap.put("text","no");
list.add(mMap); 

also, you can remove the list.add(new HashMap()); as that adds an empty map to your list that is never populated.