读取图像时出现内存不足错误

Question

All right, so I am reading images in a subdirectory in the .jar file called 'images', and of course I have to access them via a stream because it's in a .jar. This is what reads the images:

    private Image wPawn = getImage(getClass().getResourceAsStream("images/WhitePawn.png")),
        bPawn = getImage(getClass().getResourceAsStream("images/BlackPawn.png")),
        wRook = getImage(getClass().getResourceAsStream("images/WhiteRook.png")),
        bRook = getImage(getClass().getResourceAsStream("images/BlackRook.png")),
        wKnight = getImage(getClass().getResourceAsStream("images/WhiteKnight.png")),
        bKnight = getImage(getClass().getResourceAsStream("images/BlackKnight.png")),
        wBishop = getImage(getClass().getResourceAsStream("images/WhiteBishop.png")),
        bBishop = getImage(getClass().getResourceAsStream("images/BlackBishop.png")),
        wQueen = getImage(getClass().getResourceAsStream("images/WhiteQueen.png")),
        bQueen = getImage(getClass().getResourceAsStream("images/BlackQueen.png")),
        wKing = getImage(getClass().getResourceAsStream("images/WhiteKing.png")),
        bKing = getImage(getClass().getResourceAsStream("images/BlackKing.png"));
private Image getImage(InputStream stream){
    Image i;
    try{
        i = ImageIO.read(stream);
        stream.close();
    } catch (IOException e) {
        i = null;
    }
    return i;
}

This code works, but the chess game that runs is simply terribly behind with my mouse inputs. Before, I had a small separate class that did this same job, but it did not result in an OutOfMemoryError.

The error comes from the line with i = ImageIO.read(stream); and it is called from the image declarations. Can anyone help be figure out the best way to combtat the error?

Answer 1

Optimize/resise/compress your images. There's no way twelve PNGs representing simple chess pieces at sizes to be used in a game should take up enough space to run you out of memory, even at 32M or 64M heap sizes.

Answer 2

If you know that you must do a lot of IO (ie, reading a whole bunch of images), you can always increase the total heap consumed by your java application.

an example to do that would look like this:

java -Xms128m -Xmx256m YourClassNameHere

Throwing more resources at a problem is never a solution unless you know that there is no way around it. I would use this solution as a last resort after you have optimized your solution and have ensured that no memory is being wasted and the application really needs to use extra memory.

Answer 3

The best way to diagnose OOMs is to use a profiler. JProfiler is pretty good and I believe it has a free trial period.

Also, remember that OOMs are often misleading. Just because the OOM is thrown at one particular line doesn't actually mean that's the line that uses a lot of memory; it's just the line that used the last bit of available memory. For example:

byte[] unused = new byte[availableMemory - 1];
byte[] reallyImportant = new byte[10]; // throws OutOfMemoryError

Answer 4

Image.read() caches the image data in memory/disk.

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