Greenfoot

2014/10/27

Checking whether an object is of a specific class

2014/10/27

Say you have an object of class Bird and you want to find an intersecting object of class Sky. One way to find that object is to write:

public Sky intersectingSky()
{

   for (Sky s: getWorld().getObjects(Sky.class))
   {
        if (s ==getOneIntersectingObject(Sky.class))
      {
          return s; 
      }
   }
return null;
}

But does there not exist an easier way to do this, without having to go through all Sky objects? .

classicjimmy

2014/10/27

Never mind, I found out myself:

public Sky intersectingSky()
{
Object o = getOneIntersectingObject(Sky.class); 
Sky s = (Sky)o; 
        if (s != null)
        {            
            return s;   
        }
        
return null;
        
    }

danpost

2014/10/27

Or, more simply:

public Sky intersectingSky()
{
    return (Sky)getOneIntersectingObject(Sky.class);
}

This method, unless called from a different class or called several times, would be a bit wasteful as the code '(Sky)getOneIntersectingObject(Sky.class)' could replace the call to the method 'intersectingSky()' without making it to difficult to follow.

classicjimmy

2014/10/27

Thanks, that's really simple and beautiful.

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Checking whether an object is of a specific class