Store multiple values (of different types) under a same key using 'Map' in Java

Question

I am trying to instantiate a map structure with the following

Map<Timestamp, Test> map = new Map<Timestamp, Test>();

where Test is a class with 3 different types of variables and Timestamp is a java.sql.Timestamp type.

But I am getting the following error

Can not instantiate type Map<Timestamp, Test>

My primary objective is to create a map structure where I can store multiple values/objects (of different types) from a Class implementation under the same timestamp key.

To store multiple values within a key you can refer to HashMap with multiple values under the same key — Alvin Wong
– Alvin Wong, Commented Jun 24, 2013 at 13:37

Community · Accepted Answer · 2020-06-20 09:12:55Z

9

Map<Timestamp, Test>

You can't instantiate Map because it is interface. You need to do use one of the implementations like HashMap.
You can't store multiple values in HashMap, for same Key unless values are either collection of objects (or) array. Another alternative is Google MultiMap

edited Jun 20, 2020 at 9:12

CommunityBot

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answered Jun 24, 2013 at 13:35

kosa

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4 Comments

Joarder Kamal Over a year ago

using HashMap now I am getting the following error: HashMap cannot be resolved to a type any suggestion, pls?

kosa Over a year ago

@JoarderKamal:Make sure imports are there.

Joarder Kamal Over a year ago

Just wondering, how can I now put multiple values using the Test class variables (I have 3 variables of different types in Test). Any guidance kindly?

kosa Over a year ago

@JoarderKamal: I would suggest to add all 3 instances of Test to either ArrayList (or) HashSet etc., and add this collection to your map.

NimChimpsky · Accepted Answer · 2013-06-24 13:35:57Z

3

YOu can't instantiate an Interface.

Use HashMap on the righthand side

answered Jun 24, 2013 at 13:35

NimChimpsky

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Comments

JHS · Accepted Answer · 2013-06-24 13:36:14Z

3

Map is an interface. You cannot instantiate an interface.

You need to use a class that implements the Map interface. Have a look here.

answered Jun 24, 2013 at 13:36

JHS

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Comments

Ridcully · Accepted Answer · 2013-06-24 13:37:09Z

2

Do this:

Map<Timestamp, Test> map = new HashMap<Timestamp, Test>();

answered Jun 24, 2013 at 13:37

Ridcully

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Comments

Juned Ahsan · Accepted Answer · 2013-06-24 13:37:48Z

2

Do this

Map<Timestamp, Test> map = new HashMap<Timestamp, Test>();

instead of

Map<Timestamp, Test> map = new Map<Timestamp, Test>();

as you cannot instantiate the interface Map

The other thing you have mentioned that you want to store the values of different types, so use Object as the value instead of Test:

Map<Timestamp, Object> map = new HashMap<Timestamp, Object>();

answered Jun 24, 2013 at 13:37

Juned Ahsan

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1 Comment

Joarder Kamal Over a year ago

Thanks for the guide. No more error message now. Btw, I actually wanted to use multiple values of different types not a single Object (of different type).

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