Enumerating Jar file entries

At the risk of invoking the wrath and contempt of forum watchers the world over, I wish to reopen this can of worms.
I'm writing a Java program to play cribbage, and I have finally succeeded in getting it to run as a jar. My package structure for the jar is as follows.
cribbage (contains all the cribbage-specific processing)
.....images (contains board.png)
cards (contains general card-related processing)
.....images (contains cards*.png, backs*.png)
common
.....util (contains combinatorial math routines)
If I run through the JarFile enumerating entries, it stops after cribbage/images. My first question is therefore "How can I get beyond cribbage/images and into cards/images, which is where I REALLY want to be?"
The cards/images part of it contains, at the moment 5 cards*.png and 3 backs*.png, defining different card face styles and card back collections, but I may wish to change those nmbers in the future, without hard coding names in the code. This is why I wish to enumerate these entries, to give a player the chance of choosing styles and card backs from a flexible set of alternatives.
Since I may write a program in future to play starchplonkers or gurglemuffins (both card games) I'd really like the card-related stuff to be separated from the cribbage stuff - same with the common stuff - but, as soon as I put cribbage into a jar I can't access any other locally written packages, unless someone can suggest a way of organizing packages more efficiently.
I have been programming for close to 40 years, but only recently decided to exploit certain aspects of Java, like packages and jars.

OK. First, here's the structure of the jar file:
F:\Java\Packages>jar tf Cribbage.jar
META-INF/
META-INF/MANIFEST.MF
cribbage/CardPanel.class
cribbage/Cribbage$1.class
cribbage/Cribbage$CribbageCardComparator.class
cribbage/Cribbage$LogFileFilter.class
cribbage/Cribbage$MsgLineRenderer.class
cribbage/Cribbage.class
cribbage/CribbageBoard.class
cribbage/CribbageDealer$RecordedGame.class
cribbage/CribbageDealer$RecordedHand.class
cribbage/CribbageDealer.class
cribbage/images/
cribbage/images/board.png
cards/Card.class
cards/CardDeck.class
cards/CardFactory.class
cards/images/
cards/images/backs1.png
cards/images/backs2.png
cards/images/backs3.png
cards/images/cards1.png
cards/images/cards2.PNG
cards/images/cards3.PNG
cards/images/cards4.png
cards/images/cards5.png
common/util/Combinations.class
common/util/Derangements.class
common/util/Hex.class
common/util/Ordinal.class
common/util/Permutations.class
common/util/StringKit.class
common/util/TestCombinations.class
..and the code:
try {
JarFile jarfile = new JarFile( "cribbage/Cribbage.jar" );
Enumeration<JarEntry> entries = jarfile.entries();
while ( entries.hasMoreElements() ) {
JarEntry entry = entries.nextElement();
System.out.println( "Entry: " + entry + ", " + entry.getName() );
} // while
} catch (IOException e) {
e.printStackTrace(System.err);

Similar Messages

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How goes it everyone?
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www.pivotonic.com
JavaJar1.1
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Executing java apps without individual JAR file entries in CP???

Hi all,
I'm used to having to specific EACH separate jar file in the CLASSPATH when executing a java application. See the batch file example below.
Is there a way to not have to spell out EACH JAR file separately in this fashion? Eg just refer to the JAR directory?
What do people usually do here when delivering a java application to someone else, given the application has your own class files in a JAR, plus other 3rd party class files? Do you always have to build up a long JAVA batch file like the one below to enable the application to be run?
-----------example-------
c:\Progra~1\jdk1.3.1\bin\java -classpath .;deploy\mail.jar;deploy\activation.jar;deploy\xerces.jar;deploy\commons-digester.jar;deploy\commons-collections.jar;deploy\commons-beanutils.jar sns
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A simple way is to have a class inside your program load all the JAR files needed.
That way, when the main class file starts, place a call to the class that will load
the classes for you. Like this one below...
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public class MyJarLoader {
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How do I prevent Spotlight from categorizing 'JAR' files as 'Application'

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Spotlight seems to think every JAR file is an application, and because I have a lot of java applications and development stuff installed, I can no longer reliably use Spotlight to find actual applications because the search results are overflowing with useless JAR file entries.
Is there any way to configure spotlight to not classify JARS as applications? Or, alternately, can I make Spotlight ignore JARs completely? Either would save me a lot of time..
/Bill

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When I made a saved search, using the Kind drop-down menu to get the pre-defined Application, and then looked to see what criteria Spotlight was using to define "application" (and yes, the search included jar files in its results), I discovered Spotlight was NOT using the simple, straightforward "kMDItemKind=Application" as one would expect. Instead it is using something I had never heard of to define an Application, to wit "_kMDItemGroupId = 8"--furthermore, I believe characterizing applications that way has been deprecated. Be that as it may, it doesn't work to find the things you want, and exclude the things you don't.
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Francine
Schwieder

Nested jar files

two questions:
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That is: "Inner1.jar" works perfectly fine by itself, if it was the only jar file, and it has it's own main method. The same goes for "Inner2.jar". But, How can I put these two into a main jar file, "Outer.jar", and then run each of the two inner jar files?
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--jon
I've never heard of anyone wanting to do this before
but:
1. I think the only way to do this will be to use a
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This custom classloader will load your classes and you
can call your runnable classes in Inner1.jar and
Inner2.jar using seperate threads. You need a custom
classloader because if you launch you .jar from (for
example) "D:\myJar\Outer.jar" and specify the
classpath (in the JAR manifest file) to (for example)
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"lib/Inner1.jar" it will look in
"D:\myJar\lib\Inner1.jar". You're going to have
problems though because you're basically running 3
programs in 1 JVM. Things like static variables and
security are going to be an issue. Basically unless
there is a very good reason to do this, it sounds like
a bad idea.
2. Yes.

*.jar file association setting

I use J2Sdk1.3.1_04 with Windows XP professional. I have a problem with the *.jar file association setting and I need someone's help on how to correct this. Anyone?

In Windows Explorer menu: Tools | Folder Options | File Types, select jar file entry, click Advanced, and use what I posted to for the open action.

Add entries to a Jar-File

I try to add an entry to a jar File,
by using the following code:
String jarFile = new String("/home/xyz/test.jar");
JarOutputStream jos = new JarOutputStream (new FileOutputStream(jarFile));
/* this one doesn't work either ->
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* JarOutputStream jos = new JarOutputStream (new FileOutputStream(jarFile,true));
JarEntry newEntry = new JarEntry("test.class");
jos.putNextEntry(newEntry);
//...write something in new Entry...
jos.close();But instead of appending the new entry, the code overwrites the file test.jar with a new archive.
any ideas would help me very much ! thx !

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Alin.

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Main-Class: J3Ed
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Loading jar files at execution time via URLClassLoader

Hello�All,
I'm�making�a�Java�SQL�Client.�I�have�practicaly�all�basic�work�done,�now�I'm�trying�to�improve�it.
One�thing�I�want�it�to�do�is�to�allow�the�user�to�specify�new�drivers�and�to�use�them�to�make�new�connections.�To�do�this�I�have�this�class:�
public�class�DriverFinder�extends�URLClassLoader{
��private�JarFile�jarFile�=�null;
��
��private�Vector�drivers�=�new�Vector();
��
��public�DriverFinder(String�jarName)�throws�Exception{
��super(new�URL[]{�new�URL("jar",�"",�"file:"�+�new�File(jarName).getAbsolutePath()�+"!/")�},�ClassLoader.getSystemClassLoader());
��jarFile�=�new�JarFile(new�File(jarName));
��
��/*
��System.out.println("-->"�+�System.getProperty("java.class.path"));
��System.setProperty("java.class.path",�System.getProperty("java.class.path")+File.pathSeparator+jarName);
��System.out.println("-->"�+�System.getProperty("java.class.path"));
��*/
��
��Enumeration�enumeration�=�jarFile.entries();
��while(enumeration.hasMoreElements()){
��String�className�=�((ZipEntry)enumeration.nextElement()).getName();
��if(className.endsWith(".class")){
��className�=�className.substring(0,�className.length()-6);
��if(className.indexOf("Driver")!=-1)System.out.println(className);
��
��try{
��Class�classe�=�loadClass(className,�true);
��Class[]�interfaces�=�classe.getInterfaces();
��for(int�i=0;�i<interfaces.length;�i++){
��if(interfaces.getName().equals("java.sql.Driver")){
��drivers.add(classe);
��}
��}
��Class�superclasse�=�classe.getSuperclass();
��interfaces�=�superclasse.getInterfaces();
��for(int�i=0;�i<interfaces.length;�i++){
��if(interfaces[i].getName().equals("java.sql.Driver")){
��drivers.add(classe);
��}
��}
��}catch(NoClassDefFoundError�e){
��}catch(Exception�e){}
��}
��}
��}
��
��public�Enumeration�getDrivers(){
��return�drivers.elements();
��}
��
��public�String�getJarFileName(){
��return�jarFile.getName();
��}
��
��public�static�void�main(String[]�args)�throws�Exception{
��DriverFinder�df�=�new�DriverFinder("D:/Classes/db2java.zip");
��System.out.println("jar:�"�+�df.getJarFileName());
��Enumeration�enumeration�=�df.getDrivers();
��while(enumeration.hasMoreElements()){
��Class�classe�=�(Class)enumeration.nextElement();
��System.out.println(classe.getName());
��}
��}
It�loads�a�jar�and�searches�it�looking�for�drivers�(classes�implementing�directly�or�indirectly�interface�java.sql.Driver)�At�the�end�of�the�execution�I�have�found�all�drivers�in�the�jar�file.
The�main�application�loads�jar�files�from�an�XML�file�and�instantiates�one�DriverFinder�for�each�jar�file.�The�problem�is�at�execution�time,�it�finds�the�drivers�and�i�think�loads�it�by�issuing�this�statement�(Class�classe�=�loadClass(className,�true);),�but�what�i�think�is�not�what�is�happening...�the�execution�of�my�code�throws�this�exception
java.lang.ClassNotFoundException:�com.ibm.as400.access.AS400JDBCDriver
��at�java.net.URLClassLoader$1.run(URLClassLoader.java:198)
��at�java.security.AccessController.doPrivileged(Native�Method)
��at�java.net.URLClassLoader.findClass(URLClassLoader.java:186)
��at�java.lang.ClassLoader.loadClass(ClassLoader.java:299)
��at�sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:265)
��at�java.lang.ClassLoader.loadClass(ClassLoader.java:255)
��at�java.lang.ClassLoader.loadClassInternal(ClassLoader.java:315)
��at�java.lang.Class.forName0(Native�Method)
��at�java.lang.Class.forName(Class.java:140)
��at�com.marmots.database.DB.<init>(DB.java:44)
��at�com.marmots.dbreplicator.DBReplicatorConfigHelper.carregaConfiguracio(DBReplicatorConfigHelper.java:296)
��at�com.marmots.dbreplicator.DBReplicatorConfigHelper.<init>(DBReplicatorConfigHelper.java:74)
��at�com.marmots.dbreplicator.DBReplicatorAdmin.<init>(DBReplicatorAdmin.java:115)
��at�com.marmots.dbreplicator.DBReplicatorAdmin.main(DBReplicatorAdmin.java:93)
Driver�file�is�not�in�the�classpath�!!!�
I�have�tried�also�(as�you�can�see�in�comented�lines)�to�update�System�property�java.class.path�by�adding�the�path�to�the�jar�but�neither...
I'm�sure�I'm�making�a/some�mistake/s...�can�you�help�me?
Thanks�in�advice,
(if�there�is�some�incorrect�word�or�expression�excuse�me)

Sorry i have tried to format the code, but it has changed to �... sorry read this one...
Hello All,
I'm making a Java SQL Client. I have practicaly all basic work done, now I'm trying to improve it.
One thing I want it to do is to allow the user to specify new drivers and to use them to make new connections. To do this I have this class:
public class DriverFinder extends URLClassLoader{
private JarFile jarFile = null;
private Vector drivers = new Vector();
public DriverFinder(String jarName) throws Exception{
super(new URL[]{ new URL("jar", "", "file:" + new File(jarName).getAbsolutePath() +"!/") }, ClassLoader.getSystemClassLoader());
jarFile = new JarFile(new File(jarName));
System.out.println("-->" + System.getProperty("java.class.path"));
System.setProperty("java.class.path", System.getProperty("java.class.path")+File.pathSeparator+jarName);
System.out.println("-->" + System.getProperty("java.class.path"));
Enumeration enumeration = jarFile.entries();
while(enumeration.hasMoreElements()){
String className = ((ZipEntry)enumeration.nextElement()).getName();
if(className.endsWith(".class")){
className = className.substring(0, className.length()-6);
if(className.indexOf("Driver")!=-1)System.out.println(className);
try{
Class classe = loadClass(className, true);
Class[] interfaces = classe.getInterfaces();
for(int i=0; i<interfaces.length; i++){
if(interfaces.getName().equals("java.sql.Driver")){
drivers.add(classe);
Class superclasse = classe.getSuperclass();
interfaces = superclasse.getInterfaces();
for(int i=0; i<interfaces.length; i++){
if(interfaces[i].getName().equals("java.sql.Driver")){
drivers.add(classe);
}catch(NoClassDefFoundError e){
}catch(Exception e){}
public Enumeration getDrivers(){
return drivers.elements();
public String getJarFileName(){
return jarFile.getName();
public static void main(String[] args) throws Exception{
DriverFinder df = new DriverFinder("D:/Classes/db2java.zip");
System.out.println("jar: " + df.getJarFileName());
Enumeration enumeration = df.getDrivers();
while(enumeration.hasMoreElements()){
Class classe = (Class)enumeration.nextElement();
System.out.println(classe.getName());
It loads a jar and searches it looking for drivers (classes implementing directly or indirectly interface java.sql.Driver) At the end of the execution I have found all drivers in the jar file.
The main application loads jar files from an XML file and instantiates one DriverFinder for each jar file. The problem is at execution time, it finds the drivers and i think loads it by issuing this statement (Class classe = loadClass(className, true);), but what i think is not what is happening... the execution of my code throws this exception
java.lang.ClassNotFoundException: com.ibm.as400.access.AS400JDBCDriver
at java.net.URLClassLoader$1.run(URLClassLoader.java:198)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:186)
at java.lang.ClassLoader.loadClass(ClassLoader.java:299)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:265)
at java.lang.ClassLoader.loadClass(ClassLoader.java:255)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:315)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:140)
at com.marmots.database.DB.<init>(DB.java:44)
at com.marmots.dbreplicator.DBReplicatorConfigHelper.carregaConfiguracio(DBReplicatorConfigHelper.java:296)
at com.marmots.dbreplicator.DBReplicatorConfigHelper.<init>(DBReplicatorConfigHelper.java:74)
at com.marmots.dbreplicator.DBReplicatorAdmin.<init>(DBReplicatorAdmin.java:115)
at com.marmots.dbreplicator.DBReplicatorAdmin.main(DBReplicatorAdmin.java:93)
Driver file is not in the classpath !!!
I have tried also (as you can see in comented lines) to update System property java.class.path by adding the path to the jar but neither...
I'm sure I'm making a/some mistake/s... can you help me?
Thanks in advice,
(if there is some incorrect word or expression excuse me)

Images in a JAR file

Hi all,
I need see by code all the names of the resources (Images) that are includes into a JAR file. There are some function that do that work?.
Thanks in advance!!
Salvador Huertas.

For example          /* test.jar is a jar file containing some files, one directory named traffic
             and some files in the traffic directory. */
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          Enumeration enum = jf.entries();
          ArrayList list = new ArrayList();
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Read filenames from jar-file

Hi,
I want to read image names in a jar-file directory in a web start application. This used to work in previous versions of jdk,
but when I use jdk 1.6.0_20 I get this errormessage:
"http:\server:8080\test\client.jar The filename, directory name, or volume label syntax is incorrect".
Why doesn´t this work anymore?
Some of my code looks like this:
     getFiles("images/toolbuttons/val/", ".gif", true);
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         boolean removePath)
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          String jarFilePath = jarFileFinder.getClassLocation(
              this.getClass().getName());
          String[] files = null;
          try
               if (fileNameEnd != null)
                    fileNameEndFilter = new FileNameEndFilter(fileNameEnd);
               files = getFilesInJar(jarFilePath, fileNameEndFilter, catalog,
                   removePath);
          catch (Exception e)
               MessageUtil.messageOk(null, this.getClass().getName(), e.getMessage());
          return files;
     private String[] getFilesInJar(String jarFilePath, FilenameFilter filter,
         String catalog, boolean removePath)
         throws Exception
          ZipFile zipFile = new ZipFile(jarFilePath);
          Enumeration e = zipFile.entries();
          String name;
          ZipEntry zipEntry;
          ArrayList filesList = new ArrayList();
          while (e.hasMoreElements())
               zipEntry = (ZipEntry) e.nextElement();
               name = zipEntry.getName();
               if ((filter == null || !filter.accept(null, name)) ||
                   (catalog != null && !name.startsWith(catalog)))
                    continue;
               if (removePath == true)
                    name = name.substring(name.lastIndexOf("/") + 1);
               filesList.add(name);
          String[] files = new String[filesList.size()];
          for (int i = 0; i < filesList.size(); i++)
               String s = (String) filesList.get(i);
               files[i] = s;
          return files;
public class JarFileFinder
     public String getClassLocation(String classname)
          try
               Class clazz = Class.forName(classname);
               if (clazz == null) return null;
               URL url =
                   clazz.getProtectionDomain().getCodeSource().getLocation();
               String location = url.toString();
               if (location.startsWith("jar"))
                    url = ((JarURLConnection)
                        url.openConnection()).getJarFileURL();
                    location = url.toString();
               if (location.startsWith("file"))
                    return new File(URLDecoder.decode(url.getFile(), "UTF-8")).getAbsolutePath();
               else
                    return URLDecoder.decode(url.toString(), "UTF-8");
          catch (Exception e)
               MessageUtil.messageOk(null, this.getClass().getName(), e.getMessage());
          return null;
}

AndrewThompson64 wrote:
Lisa_R wrote:
..I tried to remove the URLDecoder, but the result was the same. I still get:
"http:\server:8080\test\client.jar The filename, directory name, or volume label syntax is incorrect".Given an URL should use '/' as opposed to '\', and starts with 2 '/' rather than one, it is not surprising that URL was rejected. Strange as it may seem, programming by typing random characters into an editor will rarely, if ever, work to create a working application.Yes, I agre that it´s not that surprising that the URL was rejected (even though the URL work in firefox and IE). But I didn´t write it that way. The code that put the URL together worked fine in previous versions of the jdk.
>
..The reason why I want to read the filenames from the jar instead of including a list of the names is that if you
want to add an image then all you have to do is include it in the directory.. That is largely irrelevant, since the Jar needs to be freshly built, uploaded by the developer, and downloaded by the client. Since all of that needs to be done for the addition of a single image, you might as well add an Ant task to the build that provides a single file (like I suggested earlier) that lists the resources of interest. It would take less time to write an Ant task, than debug all the hoops the code is currently jumping through(1) in order to get the information of interest.
If this was the only place were this method was used I would agre with you, but unfortunatelly it´s not. The application dosen´t only read image filenames it also reads class-names.
1) And even if you got that working, it would be likely that Sun would introduce some change in the next version of Java that breaks it again. My advice is to stop fighting it, and go with the flow.Thats not good of course! But it has been working for a long time, so I think I will try to make it work again....
Is there someone out there who has done this or knows how to do it I would appreciate some help! :-)

Find a class under Jar file

Hi all,
If I want to find out a class resides under what jar file, under Linux, I use this command:
for i in $(find -name \*.jar) ; do if jar tf $i | grep �q className.class ; then echo $i ; fi ; done
Does anybody know how can I do this under Windows? If I need to know a class is under what jar file, is there anyway to do this except extracting each jar file and see what classes are under the jar file?
Is there any tool that can mount the jar file and expand it in a tree structure to see all of it's classes visually?
Any help is greatly appreciated.

if you have a lot of jars, its actually time-consuming....Sorry, my computer freez.
Vector<String> parcalar=null;
          try {
          JarFile jarfile = new JarFile(new File("lang.jar"));
          Enumeration<JarEntry> dosyalar=jarfile.entries();
          parcalar=new Vector<String>();
          System.out.println(jarfile.size()-2);
          while(dosyalar.hasMoreElements()) {
               JarEntry entry = dosyalar.nextElement();
               String name=entry.getName();
               if(name.equals("MessagesBundle.properties")) {
                    //parcalar="--------------------";
               else if(name.equals("META-INF/MANIFEST.MF")) {
               else {
                    parcalar.addElement(name);
          catch(IOException ex){
               ex.printStackTrace();
System.out.println(parcalar);

Loading icons from jar file

Hello,
i am trying to load ALL imagefiles from my jar file. i do the following:
Class clazz = Class.forName("com.xxx.IconSelectionDialog");
String me = clazz.getName().replace(".", "/") + ".class";
dirURL = clazz.getClassLoader().getResource(me);
if (dirURL.getProtocol().equals("jar")) {
String jarPath = dirURL.getPath().substring(6, dirURL.getPath().indexOf("!")); //strip out only the JAR file
JarFile jar = new JarFile(jarPath );
Enumeration<JarEntry> entries = jar.entries(); //gives ALL entries in jar
while (entries.hasMoreElements()) {
JarEntry nextEntry = entries.nextElement();
String jarEntryName = nextEntry.getName();
this works fine with my debug local jws installation. when i try to run it online starting i get an error:
java.io.FileNotFoundException: xentis.jar (Das System kann die angegebene Datei nicht finden)
     at java.util.zip.ZipFile.open(Native Method)
     at java.util.zip.ZipFile.<init>(ZipFile.java:114)
     at java.util.jar.JarFile.<init>(JarFile.java:133)
     at java.util.jar.JarFile.<init>(JarFile.java:70)
how can i load ALL icons from a jar (without knowing the filename) ?
is there a generic way to iterate over all entries of a jarfile ?
thank you
michael

Look at "Loading Images Using getResource" on this page
http://java.sun.com/docs/books/tutorial/uiswing/components/icon.html
It should provide some ideas.

Making jar files using API

hello!
I m trying to make a jar file using the API. When the jar tool is used for the same manifest file, it is correctly written and an executable jar is created. When I use the API, the jar file is made but it is nor executable. Here is that part of code:
jar = new File(parent, jarName);
System.out.println("Executing jar command...");
//create jar file here
Manifest mf = new Manifest(new FileInputStream(manifest));
fos = new FileOutputStream(jar);
jos = new JarOutputStream(new BufferedOutputStream(fos), mf);
BufferedInputStream reader = null;
byte[] data = new byte[BUFFER];
int byteCount = 0;
for(int i = 0; i < fileNames.length; i++)
System.out.println("Adding " + fileNames);
FileInputStream fis = new FileInputStream(fileNames);
reader = new BufferedInputStream(fis, BUFFER);
JarEntry entry = new JarEntry(new ZipEntry(fileNames));
jos.putNextEntry(entry);
while((byteCount = reader.read(data,0,BUFFER)) != -1)
jos.write(data, 0, byteCount);
}//end while
reader.close();
}//end for
jos.close();//close jar output stream
fos.close();
I m sure someone will be kind and intelligent enough to solve the problem. Thank you!
Umer

A jar file is simply a Zip file. So the two API's are quite similar. First, you create a CRC - that is a way to make sure that the file isn't corrupted and that all the bytes are there (it's a polynominal algorithm that returns a number which is written in the Zip(Jar) file as well). Each entry is a file or directory. Before writing any data to the Zip(Jar) file, you have to write info on the actual file (like name, path, length etc). That's why you use putNextEntry(). Each file can have it's storing methods, although the most common is to use the "default" methods (built in the ZipOutputStream/JarOutputStream)
But in this example you set the storing methods on the entry. You use the setMethod() method to switch between either storing or compression (don't know why, but in this example you don't compress the file - you should). I myself don't use the setSize() and setCompressedSize() methods at all (and it works fine). Don't know exactly what are the implications of using them. Neither do I use the setCrc() method (If I think a little, I've only used this API once - I don't use it that much), but it's quite straightforward. It's used to check that the data is ok, and since the CRC number is the result of an algorithm, it needs to know the bytes of UNCOMPRESSED data: that's why you use crc.update() on the bytes. After that you actually write all the info set before to the Zip (Jar) file using putNextEntry(). But remember that a ZipEntry doesn't have any data. You'll have to write it yourself: thus the need for the write method: Here are two small programs I used for Zipping and Unzipping. Changing them to work for Jar files is extremely simple:
//Zip.java
import java.io.*;
import java.util.zip.*;
public class Zip
     public static void main(String[] arg)
          try
               if (arg.length < 3)
                    System.out.println("Usage: java Zip <0-9> <zip file> <file 1> [file 2] [file 3] ...");
                    System.exit(0);
               System.out.println("Compressing files into file " + arg[1]);
               ZipOutputStream out = null;
               try
                    out = new ZipOutputStream(new FileOutputStream(arg[1]));
               catch (FileNotFoundException ex)
                    System.out.println("Cannot create file " + arg[1]);
                    System.exit(1);
               try
                    out.setLevel(Integer.parseInt(arg[0]));
               catch (IllegalArgumentException ex)
                    System.out.println("Illegal compression level");
                    new File(arg[1]).delete();
                    System.exit(1);
               for (int i=2; i<arg.length; i++)
                    System.out.println("\tCompressing file " + (i-1));
                    FileInputStream read = null;
                    try
                         read = new FileInputStream(arg);
                    catch (FileNotFoundException ex)
                         System.out.println("\tCannot find file " + arg[i]);
                         continue;
                    out.putNextEntry(new ZipEntry(arg[i]));
                    int av = 0;
                    while ((av = read.available()) != 0)
                         byte[] b = new byte[av < 64 ? av : 64];
                         read.read(b);
                         out.write(b);
                    out.closeEntry();
                    read.close();
                    System.out.println("\tDone compressing file " + i);
               System.out.println("Done compressing");
               out.finish();
               out.close();
          catch (Exception e)
               new File(arg[1]).delete();
               e.printStackTrace(System.err);
And the unzipping app:
//UnZip.java
import java.io.*;
import java.util.*;
import java.util.zip.*;
public class UnZip
     public static void main(String[] arg)
          try
               if (arg.length < 1)
                    System.out.println("Usage: java UnZip <zip file> [to dir]");
                    System.exit(0);
               String dir = "";
               if (arg.length > 1)
                    dir = arg[1] + System.getProperty("file.separator");
                    File f = new File(arg[1]);
                    if (!f.exists()) f.mkdirs();
               System.out.println("Decompressing files from file " + arg[0]);
               ZipFile read = null;
               try
                    read = new ZipFile(arg[0]);
               catch (ZipException ex)
                    System.err.println("Zip error when reading file " + arg[0]);
                    System.exit(1);
               catch (IOException ex)
                    System.err.println("I/O Exception when reading file " + arg[0]);
                    System.exit(1);
               Enumeration en = read.entries();
               while (en.hasMoreElements())
                    ZipEntry entry = (ZipEntry) en.nextElement();
                    System.out.println("\tDecompressing file " + entry.getName());
                    FileOutputStream out;
                    try
                         out = new FileOutputStream(dir + entry.getName());
                    catch (FileNotFoundException ex)
                         System.err.println("\tCannot write down to file " + dir + entry.getName());
                         continue;
                    InputStream re = read.getInputStream(entry);
                    int nRead = 0;
                    for (byte[] buffer = new byte[1024]; (nRead = re.read(buffer)) != -1; out.write(buffer, 0, nRead));
                    out.close();
                    System.out.println("\tDone decompressing file " + entry.getName());
               read.close();
               System.out.println("Done decompressing files");
          catch (Exception e)
               new File(arg[1]).delete();
               e.printStackTrace(System.err);

Enumerating Jar file entries

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