Dynamically calling method

[stian.hoiland]

int choice = 0;
Scanner scanner = new Scanner(System.in);
choice = scanner.nextInt();
(...)
Method[B](choice)[/B] method = new Method[B](choice)[/B]();

The problem here is the "(choice)" part. How can you do this whitout a switch?

In the case of choice == 1:
Method(choice) should be "Method1".
In the case of choice == 2:
Method(choice) should be "Method2".
etc...

[DarrylBurke]

How can you do this whitout a switch?

if-else?

db

[stian.hoiland]

I don't see how that would solve the problem. Example?

[Fubarable]

I don't see how that would solve the problem. Example?

?
Do you understand if/else blocks? A switch statement is not much more than a glorified bunch of if/else blocks, also known as syntactic sugar. I think you should be able to create an example yourself... why not give it a try?

[stian.hoiland]

As far as I can see the problem is not what kind of loop to use.

int choice = 0;
Scanner scanner = new Scanner(System.in);
choice = scanner.nextInt(); //capture choice
(...)
Car[B](choice)[/B] volvo = new Car[B](choice)[/B](); //contruct Car based on choice. NOTE: this is pseudocode.

There will be different Cars in different files called Car1, Car2, etc... I want to create the right Car, and that is the Car choosen by the user and stored in choice.


The obvious way to do this is:

switch (choice) {
            case 1:  Car[B][U]1[/U][/B] volvo = new Car[B][U]1[/U][/B](); break;
            case 2:  Car[B][U]2[/U][/B] bmw = new Car[B][U]2[/U][/B](); break;
}

... but this isn't dynamic enough for me. You would have to hardcode the number of Cars, but this code is meant for a framework with an unknown/dynamic number of files containing Cars.


The above example might not make much sense semantically, but it is only an example.


Recap:

Files:
Car1.java - contains properties of Car1
Car2.java - contains properties of Car2

Program:
1. list avalible cars (Car1 and Car2)
2. capture choice of car (e.g. 2)
3. get properties from the choosen car (construct Car2)

Step 3 is where I'm stuck because I cannot find any code to do this.

Car[B](choice)[/B] volvo/bmw = new Car[B](choice)[/B]()

... is the nearest I come, but it is pseudocode.

Car2 bmw = new Car2()

... is what the code should execute.

[Fubarable]

The name of the variable means nothing. And since all your Car classes derive from the parent class Car (I assume), you could do:

Car car = null;
switch (choice) {
  case 1: 
    car = new Car1();
    break;
  case 2:
    car = new Car2();
    break;
}

Another possible solution is to create and use a factory pattern.

[stian.hoiland]

You are using a switch and therefore have to hardcode the number of Cars, which will not be known. What is a factory pattern? :o

[Fubarable]

A factory pattern is a way of encapsulating the creation of objects, and information on it can be found here: Factory pattern - Wikipedia, the free encyclopedia

Are you dynamically loading classes via a class loader? If so then perhaps you need to do this with reflection as a way solve your problem. For e.g.,

Dynamic Class Loading using Java Reflection API. Java Reflection API Tutorial | ViralPatel.net
Java Reflection: Dynamic Class Loading and Reloading

[JosAH]

?
Do you understand if/else blocks? A switch statement is not much more than a glorified bunch of if/else blocks, also known as syntactic sugar.

That is not enirely true; there's the table based switch and the 'direct' switch statement. The first form used a lookup table (ints are the keys, the addresses of the corresponding case statements form the associated values). The 'direct' form uses the int in the switch clause as an index in an array of target addresses. A bunch of if-else-if ... tests simply sequentially tests all conditions. imho this is not just syntactic sugar.

kind regards,

Jos

[Fubarable]

That is not enirely true; ....imho this is not just syntactic sugar.

Oops! thanks for the correction (as always)!