java

How to Update Eclipse Software on Linux behind proxy

Posted on by Jessica Chiang

To update eclipse software on Linux behind proxy is a bit tricky but doable and here is how:
1) Find the proxy server’s host name and your account’s authentication info
2) Open the network connection by “Windows”->”Preferences”-> “General”->”Network Connection”, select “manual” and enter the proxy information. Below is a screenshot of my setup:

Java with Greenfoot Lesson 3: Tic-Tac-Toe Game Part II

Posted on by Jessica Chiang

In the last lesson (Lesson 2), we created the Tic-Tac-Toe Board and GameBall classes. We also added GameBall objects to the Board object. In this lesson, we will add a Player class such that a Player object interacts with GameBall objects in a meaningful way.

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Java with Greenfoot Lesson4: Tic-Tac-Toe Game Part III

Posted on by Jessica Chiang

In this lesson, we will make the Board class check the game progress and stop the game once someone has won. I will then introduce the concept of Java Arrays. We will add code to constantly check whether three game balls of the same color has lined up and to mark those winning game balls.

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Use alternatives utility to update JDK

Posted on by Jessica Chiang

At the prompt, type

sudo update-alternatives --config java

The current available java installs would be displayed

Selection    Command
———————————————–
*  1           /usr/lib/jvm/jre-1.6.0-openjdk/bin/java
2           /usr/lib/jvm/jre-1.4.2-gcj/bin/java

To get out of the prompt without make changes, hit Ctrl+C

To add a new jdk, I downloaded the jdk-6u-linux-i586.bin from the Oracle Java site. Unzip it

chmod 755 jdk-6u27-linux-i586.bin
./jdk-6u27-linux-i586.bin

It unzip it to a directory jdk1.6.0_27. I moved it to /usr/lib/jvm,

mv jdk1.6.0_27 /usr/lib/jvm

Then install the jdk1.6.0_27 as a Java alternative. The number 3 is for the priority.

update-alternatives --install /usr/bin/java java /usr/lib/jvm/jdk1.6.0_27/bin/java 3

Now if you do “update-alternatives –config java” again, you would see jdk1.6.0_27 got added as a new alternative. Type 3 and hit Enter to select.

Selection    Command
———————————————–
+ 1           /usr/lib/jvm/jre-1.6.0-openjdk/bin/java
2           /usr/lib/jvm/jre-1.4.2-gcj/bin/java
3           /usr/lib/jvm/jdk1.6.0_27/bin/java
Enter to keep the current selection[+], or type selection number: 3

Test by typing “java -version”

[root@VM1 ~ ]# java -version
java version “1.6.0_27”
Java(TM) SE Runtime Environment (build 1.6.0_27-b07)
Java HotSpot(TM) Client VM (build 20.2-b06, mixed mode, sharing)

 

Create Custom Widgets using InkScape and NetBeans Visual Library

Posted on by Jessica Chiang

This blog entry shows one how to create a special widget using InkScape and NetBeans Visual Library. This is part of my effort to create a Java-based implementation of MIT’s Scratch, which is implemented in Squeak Smalltalk.

Step 1 Create JScratch Block Graphics:

First I created the image using Inkscape (steps to follow), import the image to IDE, then create two LayerWidgets, one transparent, and another opaque. Add the image to the background LayerWidget, adn the Swing component to the front LayerWidget. Finally, use the BorderFactory.createEmptyBorder function to limit the size of the swing component at the front layer.

To create the Scratch blocks, I used InkScape, the Open Source SVG editor. Here are the steps I took to create the graphic:

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