Jocstrap is a bridge between Java and Objective-C. This is needed to write Java applications for IPhone. Just in case you don’t have Cydia and Java installed on your IPhone, follow these instructions: Tutorial: install Java on the IPhone.

Here are the updates:

• JocStrap – Java/Objective-C connection library, version 1.0.2466-17 (was 1.0.2466-15),
• IPhone/Java – examples of Java applications, version 1.0.2474-15 (was 1.0.2357-14)
• Cydia Installer, version 1.0.2473-64 (was 1.0.2460-59)

Not a huge update, but still.

Just in case you don’t have Cydia and Java installed on your IPhone, follow these instructions: Tutorial: install Java on the IPhone.

This is another simple Java GUI application for the IPhone/IPod from Java Flavor Weblog. It simply shows Java system information on iPhone/iPod touch. It uses Java, JocStrap and GNU Classpath.

This application can be installed through Installer. Just add the repository http://javaflavor.cocolog-nifty.com/apptapp/. The application can be found in Java section and is called JavaSysInfo. Or just download it here: javasysinfo-092.zip. The package includes compiled class files, source java files and runnable script with an icon. Here are the sources: JavaSysInfo and JavaSysInfoController.

Note that JocStrap applications, including JavaSysInfo, currently require JocStrap, UICaboodle, JamVM, GNU Classpath, GNU Classpath Tools, Apache APR, libffi and BSD Subsystem. In most cases all this was installed during Java on IPhone installation.

Here is a screenshot of the icon and application itself:

The application consists of several files:

• HelloJava

This file that actually runs the application. It is simple bash script:

#!/bin/bash

# XXX: Java is symlink’d to here so the home button works

exec “$(dirname “$0″)”/Java -Xmx8M -Xss256K -cp /usr/share/java/sqlite.jar:/usr/share/java/jocstrap.jar:/usr/share/java/uicaboodle.jar:”$(dirname “$0″)” com.saurik.uicaboodle.Main HelloJava “$@”

• HelloJava$Contact.class
• HelloJava$Section.class
• HelloJava.class

These are compiled java class files.

• HelloJava.java

This is a source file. It is not needed to run the application. Just for developers to take a look. By the way here it is with syntacs highlighted: HelloJava.java

• Info.plist

This is a xml description file, contains info about executable and etc.

That’s it. Quite simple.

Using this example it is easy to create your own GUI Java application

This is a tutorial, that shows step by step how to use installed Java on the IPhone. Just in case you do not have Java installed on your IPhone there is a tutorial how to do it.

What we need is a working jailbraked IPhone with Java Installed. I used latest firmware 1.1.4, unlocked, jailbreaked and customized by winpwn.

Step 1: Create simple Java application, compile and run.

1. Create file Java4IPhone.java and put simple Java hello-world code there. I used the following code:
2. Upload to IPhone. I used /tmp directory. For uploading I used IPhone Browser.
3. Run Terminal.
4. Use command java -fullversion or jamvm -fullversion to see if java is avaliable.
5. Use command jikes to invoke java compiler.
6. Go to /tmp directory, using command cd /tmp
7. Compile. We need to specify classpath to basic java packages. If we do not do that, jikes will produce an error (see screenshot). So use the following command: jikes Java4IPhone.java -cp /usr/lib/rt.jar
8. After compiling Java4IPhone.class file should appear in the same directory. To run use commandjava Java4IPhone
9. Take a look at the screenshots. Hopefully you’ll have something similar.

Step 2: Have fun!

This is a tutorial, that shows step by step how to install Java on the IPhone.

What we need is a working unlocked and jailbraked IPhone with Installer. I used latest firmware 1.1.4, unlocked, jailbreaked and customized by winpwn.

First of all I’d like to say we all want to use legal IPhones and operators. So everything written below is for testing purposes only . Hopefully this technology will be avaliable on all IPhones sold worldwide. You also might need to recover your IPhone, so make sure you backed up all your data. I personally did everything without any problems and needs to recover. Everything you do is your responsibility, etc…

So let’s start, because it’s worth it! It’s just one evening and you will be able to create your personal Java application, compile and run it on the IPhone, and amaze all your friends .

There are two steps:

Step 1: Go to Installer and install Mobile Terminal and Cydia Installer.

1. Go to Settings -> General -> Auto-Lock and set it to Never. This will avoid some troubles during installation.
2. Run Installer. Repository for Terminal should be already there (BigBoss), because it is in latest Community Sources.
3. Add repository http://apptapp.saurik.com for Cydia Installer and refresh
4. Go to Install -> System
5. Find Term-vt100 – Mibile Terminal App. I used version svn278. Install it.
6. Go to System again and find Cydia Installer – The Future of the IPhone. I used version 1.0. Install it.
7. Exit. Restart IPhone. Two icons for Terminal and Cydia should appear.

Here are some screenshots for Step1:

Step 2: Go to Cydia Installer and install Java.

1. Run Cydia Installer.
2. Go to Install – Java section. You will find many programms there.
3. Select IPhone/Java. It will install most of the needed packages, which includes vm, libraries, etc.
4. Click confirm and wait a little bit.
5. Go to Java section again and install Jikes package (itwill be probably the only one left). Jikes is a compiler.
6. Go to Installed Packages tab. Check that Classpath, IPhone/Java, JamVM, Jikes are installed. Several other packages will be there too (Java SQLite, JocStap, etc).
7. Exit Cydia and restart IPhone. Congratulations!!! You’re done installing Java.

That’s it. The tutorial about using all this stuff is here

With this tutorial you will be able to install Java on the IPhone, compile and run simple Java applications using IPhone.

I decided to split this tutorial into two different ones. So here they are:

• Tutorial: install Java on the IPhone

• Tutorial: compile and run Java application on the IPhone

Have fun and leave comments.

There are so many posts everywhere on the internet about Skype and the IPhone. On each IPhone forum it is possible to find something similar to “Is there a version of Skype for the IPhone?”. And the answer was NO. There are some workarounds, but it’s not what users want. However there is a great possibility, that all IPhone users will hear quite soon “YES there is Skype for the IPhone”.

Skype announced a beta mobile version. It will be possible to chat, receive and make calls to Skype users and more. And it was written in… Yes, Java. So when Java will be avaliable for the IPhone all the users will be able to use Skype.

More information about Skype Mobile can be found here.

This is the simpliest Java application running on the IPhone simulator. The only thing this application does is it prints “Hello world.”. Well done! The whole world is looking forward to see more.