Thread: how to call an object with a string or variable?

Hi all,

i'd like to call an object with a String but I haven't found anything about it, how to do that.

So, you have a process, and its result is, that you get a String (result) filled with the characters lets say "house"

You have an Object named 'house' too.

Now, I would like to call the 'house' object, because String (result) = house after.

If the process gives the result 'car', than the program should call not the house object but the car object.

So for example:

String result

car called Object;

process gives a result (it can be car, or house, or whatever, ((the result is random choice from a defined number of result possibilities)) )

String result = car

calledObject = new car(); // here is the point, i don't now if the result is car or house, so for me it would look like this:
// callesObject = new result(); - so that the call calles the objcetname which the process gives


So:

So after a process I get a value for a String. And than I would like to call the Object whichs name is the same like the value of the String. How do I do that?

I hope you understand my issue, im total beginner, so sorry for the poor explanation!

Thank You very much in advance for replying!

Zoli

I'm not sure I understand, but why can't you just use a switch or an 'if' statement to create the object based on 'result'?

if ( result.equals( "car" )
{
    new Car();
}

Can you create a short code-like or pseudo code example to demonstrate what you mean?

--- Update ---

Sorry, missed a close paren:

if ( result.equals( "car" ) )
{
    new Car();
}

Hi Greg, thank you for your answer!!

Yes it would be a good solution for the first version, but later than I have to write a program, which re-writes the main program if the group of possible result will grow, and in the future it should be a very big group, like over 4000 members (later even more). So the best would be to be able to open the class with a call, in which I can use the string variable instead of giving the exact name of the object, as I don't know what the result will be.

like if:

String result;

some process that gives a value to result (car, house, dog, garden ... ...)

new result ();

would call the object that has the same name like the in result stored word. So new result (); could be: new house (); or: new house(); etc..

Or is this question if i would ask if there was a command like: do what i want (); and the program would do it...

Okay, rather than an if/switch statement with 4,000+ possible results, I recommend some kind of an event-driven system that responds appropriately to the 'result' events as they occur. An EventBus comes to mind, but there may be better options, because an EventBus with 4,000+ events is a bit ridiculous.

I'm having trouble imagining the situation where you'd have 4,000+ unique results to respond to which means 4,000+ unique objects to create to correspond to each of the 4,000+ results, etc. I'll accept it if you say it's so, but I suspect the problem can be simplified significantly.

You can do something like this:

Car someCar = (Car) create("Car");
 
public Object create(String className) {
    return Class.forName(className).newInstance();
}

But thats usually not a "safe" way to code.

Thank you guys for the answers, i will experiment a little bit with it!

Thanks for the ideas!

--- Update ---

Or is it possible to write a code that modifies the code itself?
(and anyways I came to the thing, that a create simple files instead of objects, so the problem is now: how to open a file with a string?)

So i imagine it like this:

i have txt files like car.txt, house.txt etc...

String result;

prozess gives a value to result

and here it would be great to have a command which would implement the text i give in into the program itself to the next line like:

write.programitslef("Scanner " + result + "Scanner = new Scanner (new File ("" + result + ".txt"));")

So if you run it, after you have for example 'car' for the String, to code writes to itself:

Scanner carScanner = new Scanner (new File ("car.txt));

so i could reach the stored information in the actual file, without knowing it in advance which i'll need

--- Update ---

i mean:

Scanner carScanner = new Scanner (new File ("car.txt"));