[java] Bullshit exceptions
Author
On a game I'm currently working in Java, I'm trying to get the 16 bit data from a BufferedImage. I do this by creating a BufferedImage of TYPE_USHORT_565_RGB, and set the data. I then use this statement:
DataBuffer data = image.getRaster().getDataBuffer();
to get the DataBuffer. However I need to convert the DataBuffer to DataBufferUShort to be able to retrieve data, and I also need it in an unsigned short form.
((DataBufferUShort)data).getData()
^^ That is how I do that (not the full statement by the way, don't correct syntax).
What then happens when I run it, is it causes ClassCastException. I have no idea why it is doing this. It's a direct subclass of DataBuffer. Any ideas why this might be happening?
Any help would be appreciated, thanks
Quote:
What then happens when I run it, is it causes ClassCastException. I have no idea why it is doing this. It's a direct subclass of DataBuffer.
The exception explicitly says you it is not a subclass of DataBuffer. If you ask me: I believe the computer! :-)
Although the buffer may hold unsigned data that does not guarantee that the object is a super class as you think (unless the documents say so and even then it is not sure of course).
Greetz,
Illco
Author
It's a direct subclass, and that's why I don't get why it's throwing that exception. DataBuffer - http://java.sun.com/j2se/1.4.2/docs/api/java/awt/image/DataBuffer.html
It's listed in the subclasses.
http://java.sun.com/j2se/1.4.2/docs/api/java/awt/image/DataBufferUShort.html
That extends DataBuffer.
It's listed in the subclasses.
http://java.sun.com/j2se/1.4.2/docs/api/java/awt/image/DataBufferUShort.html
That extends DataBuffer.
DataBufferUShort is a subclass of DataBuffer, so it would be cool if you turned a DataBufferUShort into a DataBuffer. But you're trying to go backwards. A DataBuffer can't necessarily be casted into a DataBufferUShort.
Let's say Cat is a subclass of an Animal. If someone gives me a random Animal, I can't necessarily start feeding it cat food.
Let's say Cat is a subclass of an Animal. If someone gives me a random Animal, I can't necessarily start feeding it cat food.
Ok. So generally: B extends A. But that does not mean that every instance of A is also a B! It just says that some instances of B are also A's.
DataBufferUShort extends DataBuffer. So some instances of DataBuffer are in fact DataBufferUShort's. But it is not true that you can cast any DataBuffer to a DataBufferUShort. In this particular case it seems you can not.
@pinacolade: well you could try to feed it cat food but you better be careful what type it actually was. :-)
DataBufferUShort extends DataBuffer. So some instances of DataBuffer are in fact DataBufferUShort's. But it is not true that you can cast any DataBuffer to a DataBufferUShort. In this particular case it seems you can not.
@pinacolade: well you could try to feed it cat food but you better be careful what type it actually was. :-)
Quote:Original post by Ganoosh_
On a game I'm currently working in Java, I'm trying to get the 16 bit data from a BufferedImage. I do this by creating a BufferedImage of TYPE_USHORT_565_RGB, and set the data.
Obviously then your creation isn't doing what you think it is. I can't see anything that says that USHORT_565 actually uses a UShort buffer behind the scenes, as such you're not guranteed to get anything specific back. Have a look in the debugger (or print the data.class to System.out) and see what class it *actually* is. You'll probably find its actually using a different internal format.
In general, explicit casts like this are bad unless it specifically mentions that such casts will work! Otherwise just work with the interface you've been given.
Quote:Original post by Anonymous Poster
i just glanced at this thread, so sorry if i repeat.
try not using java
Ya, good one! :p
Can't have those damn exceptions and crap, enforcing correctness, and everything! :P
Include the stack trace from the exception. Sometimes that will tell you what the real class is.
Lazy man's exception handling (well you could remove the print statement to be lazier) hehe.. and change the IOException to a more general Exception for total slacking.
try { someBullshitThatThrowsAnIOException();} catch (IOException e) { System.out.print("IOException thrown by someBullshitThatThrowsAnIOException()"); e.printStackTrace()}This topic is closed to new replies.
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