fishes extends actor piranha1 extends piranhas piranhas extend actor bloodstain extends actor thanks!

I would think a piranha would be considered a fish and therefore it should extend fishes -- not that this is such big deal, however. I do now see something in you original code posting that is a bit off and you should probably have mentioned you were getting an error message saying something like "method 'addObject(Actor)' not found" or maybe something about wrong number of argument. This line: cannot compile as is. The 'addObject' method of the World class uses one Actor object (the actor to add into the world) and two ints (the x and y coordinates where the actor is to be added at). You are missing the location at which the actor is to be placed. When you get a message like that, search the class documentation for the method and see how it should be used.

yep, but in the fishes class are just the prey fishes; ^^ without BloodStain bloodstain = new BloodStain(); world.addObject (bloodstain); it works fine, but i just want that the bloodstain appears one the same place as the fish who just disappeared; is that possible?

You can apply any public method to the variable 'fish' which is of Actor type; but, for its location, it must be done prior to removing the 'fish' from the world.

Yes. You must supply the appropriate location (X and Y coordinates) as parameters to the 'addObject' method. The bloodstain will then be added at these coordinates.

thanks for your help; but thats the problem that i don't know the exact location because it always depends on where you eat the fish. at exactly that point, the bloodstains should appear; how can i manage to do that? btw: merry xmas! :)

Use the pre-defined method from the Actor class to get the values you need. See the Actor class documentation and review what methods are available if you still are not sure what to do.

Merry Christmas! I feel like this needs further explication. We are trying to lead you to the solution on your own but I'm not sure you are really understanding. So, let me try again: You need to add one object at the location of another. You say that you can't specify the co-ordinates to add the object because you don't know what they are. However, you don't need to provide literal values such as '124' or '57'; you can use expressions which evaluate to a number. In this case, you want to use two expressions - one for the x coordinate and one for the y coordinate. What I mean by 'expression' is 'something that gives a value'. For example, a method call usually qualifies as an expression. You can use documented methods to retrieve the x and y co-ordinates of either the fish or the object which is doing the eating, and use the resulting values as parameters to the world's 'addObject' method. If you're still confused, let me start with a simpler problem which forms part of the larger one you're now dealing with: how can you get the co-ordinates of the fish, i.e. which method would you call (look it up in the documentation if you don't know) - and how do you write that method call? If you can answer this, we can guide you to the next step.

thanks; so i managed to do a bloodstain moving from right to left and kind of replace the fish; i get no syntax errors but if i eat a fish, i get an error code. thats the code of the fish to be eaten: public void die() { Actor piranhas = getOneIntersectingObject(Piranhas.class); if(piranhas!= null) { Greenfoot.playSound("BloodSplatter.mp3"); World world; world = getWorld(); Waterworld waterworld = (Waterworld)world; Counter counter = waterworld.getCounter(); counter.addScore(); getWorld().removeObject(this); getWorld().addObject(new BloodStain(), getX(), getY()); } } and thats the code of the bloodstain (sorry its a bit long): public class BloodStain extends Actor { GreenfootImage bloodstain1 = new GreenfootImage("bloodstain1(klein).png"); GreenfootImage bloodstain2 = new GreenfootImage("bloodstain2(klein).png"); GreenfootImage bloodstain3 = new GreenfootImage("bloodstain3(klein).png"); GreenfootImage bloodstain4 = new GreenfootImage("bloodstain4(klein).png"); GreenfootImage bloodstain5 = new GreenfootImage("bloodstain5(klein).png"); GreenfootImage bloodstain6 = new GreenfootImage("bloodstain6(klein).png"); GreenfootImage bloodstain7 = new GreenfootImage("bloodstain7(klein).png"); GreenfootImage bloodstain8 = new GreenfootImage("bloodstain8(klein).png"); public int animationCounter; public int frame = 1; public void act() { animationCounter = animationCounter + 1; if(animationCounter % 4 == 0) { animation(); } setLocation (getX()-2, getY()); // ohne das funktioniert es (fast) immer } public void animation() { if(frame == 1) { setImage(bloodstain1); frame = 2; } else if(frame == 2) { setImage(bloodstain1); frame = 3; } else if(frame == 3) { setImage(bloodstain2); frame = 4; } else if(frame == 4) { setImage(bloodstain2); frame = 5; } else if(frame == 5) { setImage(bloodstain3); frame = 6; } else if(frame == 6) { setImage(bloodstain3); frame = 7; } else if(frame == 7) { setImage(bloodstain4); frame = 8; } else if(frame == 8) { setImage(bloodstain4); frame = 9; } else if(frame == 9) { setImage(bloodstain5); frame = 10; } else if(frame == 10) { setImage(bloodstain5); frame = 11; } else if(frame == 11) { setImage(bloodstain6); frame = 12; } else if(frame == 12) { setImage(bloodstain6); frame = 13; } else if(frame == 13) { setImage(bloodstain7); frame = 14; } else if(frame == 14) { setImage(bloodstain7); frame = 15; } else if(frame == 15) { setImage(bloodstain8); frame = 16; } else if(frame == 16) { setImage(bloodstain8); frame = 17; } else if(frame == 17) { getWorld().removeObject(this); } } } and thats the error message i get: java.lang.IllegalStateException: Actor not in world. An attempt was made to use the actor's location while it is not in the world. Either it has not yet been inserted, or it has been removed. at BabyNemo.die(BabyNemo.java:59) at BabyNemo.act(BabyNemo.java:18) at BloodStain.act(BloodStain.java:26) i have different codes for removing the fish: for example if you eat it or it just reaches the left corner of the game; and the bloodstain should disappear after the animation or if it reaches the left corner too; i don't just want one removing code

So, read the error message: Looking at your code, this seems right. You've got this: It does exactly what the error says: removes an object (this) from the world, and then asks for its position (getX(), getY()) when it is no longer in the world. The fix is obvious: reverse the order of the two statements. By the way, when you post here, there are a bunch of links below the text box that you type into. One of them says: Posting code? read this! Seeing as you are posting code, you need to click that link. It explains how you should use 'code' tags to properly format the code.

Well, it can be done both ways -- as two separate removing codes or as two separate conditions within the same 'if' that removes the actor. That is: In the second way, condition two will not be checked if condition one was true -- so, no exceptions will be thrown and the extra check to ensure the actor is still in the world to check the second condition is not needed (since both checks are done prior to the actor being removed). Hope that made some sense.