Java example source code file (Comment.java)

This example Java source code file (Comment.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

comment, exception, fileoutputstream, inputstream, ioexception, randomaccessfile, string, stringbuffer, test, utf8, zip, zipentry, zipfile, zipoutputstream

The Comment.java Java example source code

/*
 * Copyright (c) 2003, 2011, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

/* @test
   @bug 4334846
   @summary Make sure zip file comments of various sizes can be written.
   @author Martin Buchholz
 */

import java.io.*;

import java.util.zip.ZipEntry;
import java.util.zip.ZipFile;
import java.util.zip.ZipOutputStream;

public class Comment {
    private static final String entryName = "entryName";
    private static final String entryContents = "entryContents";
    private static final int commentMaxLength = 0xFFFF;
    private static final int [] commentLengths
        = { 0, 1, 32768, commentMaxLength - 1, commentMaxLength };

    public static void main(String argv[])
        throws Exception
    {
        for (int i = 0; i < commentLengths.length; ++i) {
            int commentLength = commentLengths[i];
            String comment = buildComment(commentLength);
            String name = "Test" + commentLength + ".zip";
            writeZipFile(name, comment);
            verifyZipFile(name, comment);
            new File(name).delete();
            System.out.println(commentLength + ": successful");
        }
    }

    private static void writeZipFile(String name, String comment)
        throws IOException
    {
        try (FileOutputStream fos = new FileOutputStream(name);
             ZipOutputStream zos = new ZipOutputStream(fos))
        {
            zos.setComment(comment);
            ZipEntry ze = new ZipEntry(entryName);
            ze.setMethod(ZipEntry.DEFLATED);
            zos.putNextEntry(ze);
            new DataOutputStream(zos).writeUTF(entryContents);
            zos.closeEntry();
        }
    }

    private static void verifyZipFile(String name, String comment)
        throws Exception
    {
        // Check that Zip entry was correctly written.
        try (ZipFile zipFile = new ZipFile(name)) {
            ZipEntry zipEntry = zipFile.getEntry(entryName);
            InputStream is = zipFile.getInputStream(zipEntry);
            String result = new DataInputStream(is).readUTF();
            if (!result.equals(entryContents))
                throw new Exception("Entry contents corrupted");
        }

        try (RandomAccessFile file = new RandomAccessFile(name, "r")) {
            // Check that comment length was correctly written.
            file.seek(file.length() - comment.length()
                      - ZipFile.ENDHDR + ZipFile.ENDCOM);
            int b1 = file.readUnsignedByte();
            int b2 = file.readUnsignedByte();
            if (b1 + (b2 << 8) != comment.length())
                throw new Exception("Zip file comment length corrupted");

            // Check that comment was correctly written.
            file.seek(file.length() - comment.length());
            byte [] bytes = new byte [comment.length()];
            file.readFully(bytes);
            if (! comment.equals(new String(bytes, "UTF8")))
                throw new Exception("Zip file comment corrupted");
        }
    }

    private static String buildComment(int length) {
        StringBuffer result = new StringBuffer();
        while (result.length() < length) {
            /* Endhdr is 22 bytes long, so this pattern makes it easy
             * to see if it is copied correctly */
            result.append("abcdefghijklmnopqrstuvABCDEFGHIJKLMNOPQRSTUV");
        }
        String string = result.toString();
        string = string.substring(string.length() - length);
        return string;
    }
}