Question

I use below method for reading a binary file :

public void readFile()
{
    try
    {
        Reader in = new InputStreamReader( this.getClass().getResourceAsStream( this.fileName));
        int count = (in.read() * 0xFF) + in.read();
        int heights = in.read();

        this.shapes = new int[count][];
        for(int ii = 0;ii<count;ii++)
        {
            int gwidth = in.read();
            int[] tempG = new int[gwidth * heights];
            int len = (in.read() * 0xff) + in.read();
            for(int jj = 0;jj<len;jj++)
            {
                tempG[top++] = in.read() * 0x1000000;
            }
            this.shapes[ii] = tempG;
        }
        in.close();

    }catch(Exception e){}
}

It works perfectly in netbeans emulator and some devices,but in some devices and in kemulator it seems that in.read(), read a char (two byte), and it causes my app crashes on those device and emulator.

what is the best method for reading file in bytes?

Answer 1

Since you are always dealing with bytes, you should use an InputStream rather than an InputStreamReader.

Add the Javadoc says:

An InputStreamReader is a bridge from byte streams to character streams: It reads bytes and decodes them into characters using a specified charset. The charset that it uses may be specified by name or may be given explicitly, or the platform’s default charset may be accepted.

And the read() method reads a “character”:

On the other hand, an InputStream represents an input stream of bytes:

public abstract int read() throws IOException

Reads the next byte of data from the input stream. The value byte is returned as an int in the range 0 to 255. If no byte is available because the end of the stream has been reached, the value -1 is returned. This method blocks until input data is available, the end of the stream is detected, or an exception is thrown.

(And for kicks, here’s a dated article about “buffered readers” in j2me)