JAVA variable as 2 types

Question

How can I create value of type String and also Collection?

I want someTimes put in this Strings and the othertimes put collections.

for example in javascript I would do

 var k;
 if (someBoolean){
    k=1;
 } else{
    k=[1,2,3];
 }

can I get this behavior of the variable in java, hack or something?

I found Solution: I created an interface and declear this Objects as this interface.

Please be more specific. You can have a collection of Strings, or you could serialize some collection of Strings in a [JSON](http://stackoverflow.com/q/7976643/2970947) (or [XML](http://stackoverflow.com/q/4441017/2970947)) array. — Elliott Frisch, May 04 '14 at 02:20
no array no collections of strings I have also collection and Strings I want variable that will be in some cases string and the other to put in it Collection — Alon, May 04 '14 at 02:22
Why not just use a Collection of Strings to begin with and fetch the Strings from the Collection later? — PakkuDon, May 04 '14 at 02:23
because I dont want that I will need to go into the Collection and use the get method .. — Alon, May 04 '14 at 02:24
@user3160197 Please [edit](http://stackoverflow.com/posts/23451903/edit) your question; at the moment it seems like a [XY problem](http://meta.stackexchange.com/q/66377/243725). — Elliott Frisch, May 04 '14 at 02:27
Indeed, as @ElliottFrisch states, this question seems like it's barking up the wrong tree, or perhaps even the wrong forest. Tell us your use case, why you feel you need this set up, and perhaps we can show you a better way. — Hovercraft Full Of Eels, May 04 '14 at 02:32

score 1 · Accepted Answer · answered May 04 '14 at 02:28

Java does not support union types; however, both of these types share the same base Object class, so you could assign either one of them to a variable defined like this

 Object something;
 something = "Hello World!";
 something = new ArrayList(); // this is a collection.

Odds are that you probably were thinking of a Collection of Strings, in which case, you define it like Collection<String>

 Collection<String> strings = new ArrayList<String>();
 strings.add("Hello");
 strings.add("World");
 strings.add("!");

If that's not what you wanted, and you really want to sometimes store a String and sometimes store a Collection, remember that Java enforces strict type checking. This means that variables cannot just store anything, they must store something that is type compatible.

String and Collection are too different to be considered type compatible without some seriously bad programming (like using Object) or something even stranger.

score 0 · Answer 2 · answered May 04 '14 at 02:28

You cant. String is a final class, meaning you cannot extend upon it. A String will only ever be a String. You can have a collections that contain Strings, but a String object will only have 2 types: Object and String.

You can have a class that contains a String (or a StringBuilder) and a collection, then use that class to store/receive from

JAVA variable as 2 types

2 Answers2