Compress.java Source code

Introduction

Here is the source code for Compress.java

Source

/*
 * Copyright (c) 2004 David Flanagan.  All rights reserved.
 * This code is from the book Java Examples in a Nutshell, 3nd Edition.
 * It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied.
 * You may study, use, and modify it for any non-commercial purpose,
 * including teaching and use in open-source projects.
 * You may distribute it non-commercially as long as you retain this notice.
 * For a commercial use license, or to purchase the book, 
 * please visit http://www.davidflanagan.com/javaexamples3.
 */

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.zip.GZIPOutputStream;
import java.util.zip.ZipEntry;
import java.util.zip.ZipOutputStream;

/**
 * This class defines two static methods for gzipping files and zipping
 * directories. It also defines a demonstration program as a nested class.
 */
public class Compress {
    /** Gzip the contents of the from file and save in the to file. */
    public static void gzipFile(String from, String to) throws IOException {
        // Create stream to read from the from file
        FileInputStream in = new FileInputStream(from);
        // Create stream to compress data and write it to the to file.
        GZIPOutputStream out = new GZIPOutputStream(new FileOutputStream(to));
        // Copy bytes from one stream to the other
        byte[] buffer = new byte[4096];
        int bytes_read;
        while ((bytes_read = in.read(buffer)) != -1)
            out.write(buffer, 0, bytes_read);
        // And close the streams
        in.close();
        out.close();
    }

    /** Zip the contents of the directory, and save it in the zipfile */
    public static void zipDirectory(String dir, String zipfile) throws IOException, IllegalArgumentException {
        // Check that the directory is a directory, and get its contents
        File d = new File(dir);
        if (!d.isDirectory())
            throw new IllegalArgumentException("Compress: not a directory:  " + dir);
        String[] entries = d.list();
        byte[] buffer = new byte[4096]; // Create a buffer for copying
        int bytes_read;

        // Create a stream to compress data and write it to the zipfile
        ZipOutputStream out = new ZipOutputStream(new FileOutputStream(zipfile));

        // Loop through all entries in the directory
        for (int i = 0; i < entries.length; i++) {
            File f = new File(d, entries[i]);
            if (f.isDirectory())
                continue; // Don't zip sub-directories
            FileInputStream in = new FileInputStream(f); // Stream to read file
            ZipEntry entry = new ZipEntry(f.getPath()); // Make a ZipEntry
            out.putNextEntry(entry); // Store entry
            while ((bytes_read = in.read(buffer)) != -1)
                // Copy bytes
                out.write(buffer, 0, bytes_read);
            in.close(); // Close input stream
        }
        // When we're done with the whole loop, close the output stream
        out.close();
    }

    /**
     * This nested class is a test program that demonstrates the use of the static
     * methods defined above.
     */
    public static class Test {
        /**
         * Compress a specified file or directory. If no destination name is
         * specified, append .gz to a file name or .zip to a directory name
         */
        public static void main(String args[]) throws IOException {
            if ((args.length != 1) && (args.length != 2)) { // check arguments
                System.err.println("Usage: java Compress$Test <from> [<to>]");
                System.exit(0);
            }
            String from = args[0], to;
            File f = new File(from);
            boolean directory = f.isDirectory(); // Is it a file or directory?
            if (args.length == 2)
                to = args[1];
            else { // If destination not specified
                if (directory)
                    to = from + ".zip"; // use a .zip suffix
                else
                    to = from + ".gz"; // or a .gz suffix
            }

            if ((new File(to)).exists()) { // Make sure not to overwrite
                System.err.println("Compress: won't overwrite existing file: " + to);
                System.exit(0);
            }

            // Finally, call one of the methods defined above to do the work.
            if (directory)
                Compress.zipDirectory(from, to);
            else
                Compress.gzipFile(from, to);
        }
    }
}