Bohemian Code

Generics tutorial

2006-03-28T10:34:00.000-08:00

Found this fantastic introduction to generics and many cool code snippets by Gilad Bracha. The wildcard chapter is worth the trip. Enjoy.

Generics Tutorial (pdf)

Running Ant on Mac OS X with JDK 1.5

2006-01-24T11:22:00.000-08:00

For Mac OS X's Java 1.5, the Java preferences utility allows switching versions for applets and applications launched from jars (java -jar) or JNLP (Web Start). This is described in this release note: Apple Java 1.5 Release Note.

However on the command line, ant doesn't pick up the version change even after following the tech note. The release note recommends adding $JAVA_HOME/Commands to the PATH. For Ant, it doesn't work because the ant startup script looks for 'java' in $JAVA_HOME/bin and that, dear friends, does not exist in the standard installation. This is easily solved:

(in .bashrc or equivalent)
export JAVA_HOME=/System/Library/Frameworks/JavaVM.framework/Versions/1.5

(as su)
cd $JAVA_HOME
ln -s Commands bin

That's all to it.

Prototyping with ActionListener

2006-01-22T14:56:00.000-08:00

When prototyping UIs in Swing I like to use ActionListener and a Hashtable to communicate inputs from a field to whatever needs to respond to it. Say there is a round rectangle such as:

int arcw = 8;
int arch = 8;

Shape shape =
new RoundRectangle2D.Double((double) x, (double) y, (double) w,
(double) h, (double)arcw, (double)arch);

Often with prototyping, one likes to fool around to look at various ways the UI may look. But instead of edit-recompile-test, throw in some text fields, add an ActionListener and play with it until cows come home. Like so:

class Pumper implements ActionListener {
protected Hashtable propMap = null;
protected String name = null;

public Pumper(Hashtable propMap, String name) {
this.propMap = propMap;
this.name = name;
}

public void actionPerformed(ActionEvent e) {
propMap.put(name, ((JTextField) e.getSource()).getText());
}
}

The propMap is a class field and the paint code may be modified like so:

// don't forget to initialize propMap with default "arcw" etc values!
int arcw = Integer.parseInt(((String) propMap.get("arcw")));
int arch = Integer.parseInt(((String) propMap.get("arch")));

Shape shape =
new RoundRectangle2D.Double((double) x, (double) y, (double) w,
(double) h, (double)arcw, (double)arch);

and the textfield like so:

JTextField arcwTF = new JTextField(3);
arcwTF.addActionListener(new Pumper(propMap, "arcw"));
b2.add(new JLabel("arc width:"));
b2.add(arcwTF);

That's it! Add a line code somewhere to invoke revalidate() or do what I do, resize the JFrame/JDialog a tad bit back and forth.

void main (String [] args)

2006-01-17T19:21:00.000-08:00

I like code. I like what it does. I like code with least issues and maximum potential. The author will attempt to do least amount of "I this-n-that" and most amount of "the code this-n-that". Keep coding.