import java.util.*;
 import java.util.jar.*;
 import java.util.zip.*;
 import java.io.*;
 /**
* Reads GZIP, Zip, and Jar files and outputs their content to the console.
*/
 class Zip {
 public static void main(String[] args) {
 String fileName = args[0];
 System.out.println("contents of " + fileName + "...");
 if (fileName.endsWith(".gz")) {
readGZIPFile(fileName);
 } else if (fileName.endsWith(".zip")) {
 readZipFile(fileName);
 } else if (fileName.endsWith(".jar")) {
 readJarFile(fileName);
 }
 }
 /**
 * Reads a GZIP file and dumps the contents to the console.
 */
 private static void readGZIPFile(String fileName) {
 // use BufferedReader to get one line at a time
 BufferedReader gzipReader = null;
 try {
 // simple loop to dump the contents to the console
 gzipReader = new BufferedReader(
new InputStreamReader(
 new GZIPInputStream(
 new FileInputStream(fileName))));
 while (gzipReader.ready()) {
 System.out.println(gzipReader.readLine());
 }
 gzipReader.close();
} catch (FileNotFoundException fnfe) {
 System.out.println("The file was not found: " + fnfe.getMessage());
 } catch (IOException ioe) {
 System.out.println("An IOException occurred: " + ioe.getMessage());
 } finally {
 if (gzipReader != null) {
 try { gzipReader.close(); } catch (IOException ioe) {}
 }
 }
 }

 /**
 * Reads a Zip file, iterating through each entry and dumping the contents
 * to the console.
 */
 private static void readZipFile(String fileName) {
 ZipFile zipFile = null;
 try {
 // ZipFile offers an Enumeration of all the files in the Zip file
 zipFile = new ZipFile(fileName);
 for (Enumeration e = zipFile.entries(); e.hasMoreElements();) {
 ZipEntry zipEntry = (ZipEntry) e.nextElement();
 System.out.println(zipEntry.getName() + " contains:");
 // use BufferedReader to get one line at a time
 BufferedReader zipReader = new BufferedReader(
new InputStreamReader(zipFile.getInputStream(zipEntry)));
 while (zipReader.ready()) {
 System.out.println(zipReader.readLine());
 }
 zipReader.close();
 }
 } catch (IOException ioe) {
 System.out.println("An IOException occurred: " + ioe.getMessage());
 } finally {
 if (zipFile != null) {
 try { zipFile.close(); } catch (IOException ioe) {}
 }
 }
 }

 /**
 * Reads a Jar file, displaying the attributes in its manifest and dumping
 * the contents of each file contained to the console.
 */
 private static void readJarFile(String fileName) {
 JarFile jarFile = null;
 try {
 // JarFile extends ZipFile and adds manifest information
 jarFile = new JarFile(fileName);
 if (jarFile.getManifest() != null) {
 System.out.println("Manifest Main Attributes:");
 Iterator iter =
 jarFile.getManifest().getMainAttributes().keySet().iterator();
 while (iter.hasNext()) {
 Attributes.Name attribute = (Attributes.Name) iter.next();
 System.out.println(attribute + " : " +
 jarFile.getManifest().getMainAttributes().getValue(attribute));
 }
 System.out.println();
 }
 // use the Enumeration to dump the contents of each file to the console
 System.out.println("Jar file entries:");
 for (Enumeration e = jarFile.entries(); e.hasMoreElements();) {
 JarEntry jarEntry = (JarEntry) e.nextElement();
 if (!jarEntry.isDirectory()) {
 System.out.println(jarEntry.getName() + " contains:");
 BufferedReader jarReader = new BufferedReader(
new InputStreamReader(jarFile.getInputStream(jarEntry)));
 while (jarReader.ready()) {
 System.out.println(jarReader.readLine());
 }
 jarReader.close();
 }
 }
 } catch (IOException ioe) {
 System.out.println("An IOException occurred: " + ioe.getMessage());
 } finally {
 if (jarFile != null) {
 try { jarFile.close(); } catch (IOException ioe) {}
 }
 }
 }
 }