/*
 * Copyright (c) 2001 Matthew Feldt. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided the copyright notice above is
 * retained.
 *
 * THIS SOFTWARE IS PROVIDED ''AS IS'' AND WITHOUT ANY EXPRESSED OR
 * IMPLIED WARRANTIES.
 */

/**
 * Head.java
 *
 * Java Examples In A Nutshell Copyright (c) 2000 David Flanagan
 * Exercise 3-1:
 * Write a program named Head that prints out the first ten lines of each file
 * specified on the command line.
 *
 * @author Matthew Feldt <developer@feldt.com>
 * @version 1.0, 01/30/2001 8:39
 */

package com.feldt.examples.io;
import java.io.*;


public class Head {
	public static void main (String args[]) {
		final int NUM_LINES = 10;
		final String usage = "Usage: java Head file ...";
		BufferedReader in;
		String out;

		if (args.length < 1) fail(usage);

		// print the first NUM_LINES from files supplied on the command line
		for (int i = 0; i < args.length; i++) {
			try {
				File f = new File(args[i]);
				if (! f.exists()) fail(args[i] + ": no such file or directory.");
				if (! f.canRead()) fail(args[i] + ": read protected.");
				if (! f.isFile()) fail(args[i] + ": is not a regular file.");

				in = new BufferedReader(new FileReader(f));

				// print the filename
				System.out.println("::::::::::::::");
				System.out.println(f);
				System.out.println("::::::::::::::");

				// print up to NUM_LINES from the beginning of the file
				for (int j = 0; j < NUM_LINES; j++) {
					out = in.readLine();
					if (out == null) break;
					else System.out.println(out);
				}
			} catch(IOException e) {
				System.err.println(e.getMessage());
			} catch(IllegalArgumentException e) {
				System.err.println(e.getMessage());
			}
		}
	}

	/** shorthand method to throw an exception with the appropriate message */
	protected static void fail(String msg) throws IllegalArgumentException {
		throw new IllegalArgumentException(msg);
	}
}