Understanding of classes

Question

I am new to programming and ask some questions about classes.

I use Karel as an example:

public class Karel extends robot{
   ....

}

then I expand Karel:

public class SuperKarel extends Karel{
   ....

}

but then I want to organize several groups of methods:

public class KarelJumps extends SuperKarel {
    ....

}

public class KarelColor extends SuperKarel {
    ....

}

But if I want to make a Karel jump, I need to instantiate it KarelJumpssooner SuperKarel. But since there KarelJumpsis another object, then KarelColorI could not use any of its methods.

I would just put all the methods KarelJumpsand KarelColor inside SuperKarel?I just make one big object?

Answer 1

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Answer 2

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Answer 3

, Karel KarelColor, .

KarelJumps KarelColor . , :

public class SuperKarel extends Karel
public class KarelJumps extends SuperKarel
public class KarelColor extends KarelJumps

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Answer 4

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public class Karel extends robot{
    public void jump(){
    ...
    } 

   public void setColor(Color c) {
   ...
   }

}

public class SuperKarel extends Karel{
    public void jump(){
       //jump in a super way    
    } 

   public void setColor(Color c) {
       //set some super color 
   }
}

Answer 5

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Here is myK he is a Karel

oh, I wonder what he can do ... hmmm looks like a Karel can jump

myK.jump(howHigh)

hey he jumped

wonder what else he can do ...

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Answer 6

:

• ( ).

• . KarelJumps KarelColor , " ". () , . : ( → ).

• Java "mixins", , : Mixins - , . , , , ( , , ).

• You can use a delegate. The delegate then implements this method. In two Karel classes, you add a field delegateand invoke the delegate implementation:

  interface IDelegate { void method (); }
  class Delegate implements IDelegate {
      void method () { ... }
  }
  
  public class KarelJumps extends SuperKarel implements IDelegate {
      IDelegate delegate = new Delegate ();
  
      // Instead of copying the code, delegate the work
      void method () { delegate.method (); }
  }