Am I closing my input stream correctly in Java?

Question

I created a class that extends InputStream so that I can keep count of the number of bytes being read and throw an exception if it exceeds a max limit that I define.

Her

Answer 1

If LimitedSizeInputStream extends InputStream and wraps another stream, then @areus's solution is the best one.

An alternative approach would be to extend FilterInputStream, like this:

public class LimitedSizeInputStream extends FilterInputStream
{
    private final long maxSize;
    private long total;

    public LimitedSizeInputStream(InputStream original, long maxSize)
    {
        super(original);
        this.original = original;
        this.maxSize = maxSize;
    }

    // use 'this.in' instead of 'this.original'
    // at least one of the 'read' methods needs to be overridden.
}

Note that FilterInputStream provides default implementations of the API methods that may prove useful.

The javadoc provides details of what the default method implementations do.

Answer 2

The try-with-resources only closes the declared resource. So will only close metadataStream.

You should implement the close method in LimitedSizeInputStream to close the original stream.

@Override
public void close() throws IOException {
    original.close();
}