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  1. /* package whatever; // don't place package name! */
  2.  
  3. import java.util.*;
  4. import java.lang.*;
  5. import java.io.*;
  6.  
  7. /* Name of the class has to be "Main" only if the class is public. */
  8. class Ideone
  9. {
  10. 	public static void main (String[] args) throws java.lang.Exception
  11. 	{
  12. 		GenericObject o;
  13.  
  14.         o = new Object1(10, 10);
  15.         o.wh();
  16.         System.out.println(o.w); // Output: 3 (ok)
  17.         System.out.println(o.h); // Output: 10 (ok)
  18.  
  19.         o = new Object2(10, 10);
  20.         o.wh();
  21.         System.out.println(o.w); // Output: 7 (ok)
  22.         System.out.println(o.h); // Output: 4 (ok)
  23.  
  24.         String inputFromUser = "1";
  25.  
  26.         // o = new Object + inputFromUser + (10, 10);
  27.         /*I know that is an absurd, just to illustrate...
  28. 		if polymorphism can solve this problem, I thik it's the best option. So how use it here?
  29. 		I don't wanna use ifs or switchs, I will use more than 300 classes*/
  30.  
  31. 		Class<?> typeFromUser = Class.forName("Object" + inputFromUser);
  32. 		java.lang.reflect.Constructor<?> constructor = typeFromUser.getDeclaredConstructor(Integer.TYPE, Integer.TYPE);
  33. 		Object obj = constructor.newInstance(10, 10);
  34. 		o = (GenericObject) obj;
  35.  
  36.         o.wh();
  37.         System.out.println(o.w); // Output: 3 (that's what I wanna obtain)
  38.         System.out.println(o.h); // Output: 10 (that's what I wanna obtain)
  39. 	}
  40. }
  41.  
  42. abstract class GenericObject {
  43.             int w, h, x, y;
  44.             GenericObject (int x, int y) {
  45.                 this.x = x;
  46.                 this.y = y;
  47.             }
  48.             public abstract void wh();
  49.         }
  50.         class Object1 extends GenericObject{
  51.             Object1 (int x, int y) {
  52.                 super(x, y);
  53.             }
  54.             @Override
  55.             public void wh () {
  56.                 w = 3;
  57.                 h = 10;
  58.             }
  59.         }
  60.         class Object2 extends GenericObject{
  61.             Object2 (int x, int y) {
  62.                 super(x, y);
  63.             }
  64.             @Override
  65.             public void wh () {
  66.                 w = 7;
  67.                 h = 4;
  68.             }
  69.         }
Success #stdin #stdout 0.1s 320512KB
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Standard input is empty
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3
10
7
4
3
10
https://ideone.com/7HsTsD
language:
Java (HotSpot 12)
created:
10 years ago
visibility:
public

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