Why do I get a NullPointerException?

[nessa203]

I have two classes in a package called compressor: Compressor and Reader. Compressor takes a file from the first command line argument (args[0]) and then attempts to read it into a byte array using an instance of Reader.

Compressor's code:

public class Compressor {
    File f;

    public Compressor(File file) {
            f = file;
            System.out.println("File set.");
    }
    
    public void compress() {
        try {
			r.read(f);
		} catch (Exception e) {
			System.out.println("Caught");
			e.printStackTrace();
		}
    }
    
    public static void main(String[] args) throws IOException {
		String fileName = args[0];
		File f = new File(fileName);
		Compressor c = new Compressor(f);
		c.compress();
    }

}

Reader's Code:

public class Reader {
    FileInputStream fileIn;
    byte[] in;
    
    public Reader() throws IOException {
            fileIn = null;
    }

    public byte[] read(File file) throws IOException {
            long length = file.length();
            in = new byte[(int) length];

            fileIn = new FileInputStream(file);
            int offset = 0;
            int numRead = 0;
            while (offset < in.length && (numRead = fileIn.read(in, offset, in.length-offset)) >= 0) {
            		offset = offset + numRead;
            }
            fileIn.close();
			return in;
    }
}

Both classes compile fine ("javac compressor/Compressor.java"), but when I try to run them on the command line with a file ("java compressor/Compressor 1") I get the following:
File set.
Caught
java.lang.NullPointerException
at compressor.Compressor.compress(Compressor.java:19)
at compressor.Compressor.main(Compressor.java:30)

Having looked up NullPointerExceptions, etc, I think that the program is not calling the actual file (named "1"), but I'm not sure why not.

Any advice on what I am doing wrong would be greatly appreciated!

[PhHein]

I doubt that they compile fine. r.read(f); r is not defined in Compressor. Or you've posted the wrong code.

[nessa203]

Sorry my bad code editing! It's defined just after "File f;" as "Reader r;"

[PhHein]

There you go. Where is the line r = new Reader(); ?

[nessa203]

Thank you very much! I knew it was something small and silly, but I really couldn't see it :s

[PhHein]

You're welcome.