Processing/Java - Simple example

Question

I'm trying to get a simple example to run. The below code compiles but gives me errors when I try to run it. I'm a newbie to Processing/Java. Also, my goal is to see if I can make a simple command line utility with processing for charting/graphics (very simple), kind of like gnuplot.

import processing.core.*;

public class MyProcessingSketch extends PApplet {

  public void setup() {
    size(200,200);
    background(0);
  }

  public void draw() {
    stroke(255);
    if (mousePressed) {
      line(mouseX,mouseY,pmouseX,pmouseY);
    }
  }
  public static void main(String args[]) {
    PApplet.main(new String[] { "--present", "MyProcessingSketch" });
  }
}

I build with

javac -cp location/of/core/core.jar MyProcessingSketch.java

and run with

java -cp location/of/core/core.jar MyProcessingSketch

the error I get is,

Exception in thread "main" java.lang.NoClassDefFoundError: MyProcessingSketch

EDIT:

I've now tried

java -cp "location/of/core/core.jar:." MyProcessingSketch

and the error is now,

Exception in thread "main" java.lang.RuntimeException: java.lang.NullPointerException

You're trying to run an applet as a desktop application. At best it should be loaded into a browser, at worse, you can try using the applet viewer included with the JDK — MadProgrammer
– MadProgrammer, Commented Apr 30, 2013 at 0:19
"I'm a newbie to Processing..." Why are you bothering with that primitive AWT based API? — Andrew Thompson
– Andrew Thompson, Commented Apr 30, 2013 at 1:20
As an aside, what is the --present attribute? I don't see it mentioned in the JavaDocs. — Andrew Thompson
– Andrew Thompson, Commented Apr 30, 2013 at 2:51

rgettman · Accepted Answer · 2013-04-30 00:14:26Z

4

You have set your classpath to location/of/core/core.jar, but that doesn't include the current directory where your class lies.

Include "." (the current directory) in your classpath option:

java -cp "location/of/core/core.jar:." MyProcessingSketch

The ":" is the path separator on Unix and Linux; use a semicolon on Windows instead.

java -cp "location/of/core/core.jar;." MyProcessingSketch

answered Apr 30, 2013 at 0:14

rgettman

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1 Comment

Mel Nicholson Over a year ago

@ctsa It is also a good idea to put your class in a package. Then you would run mypackage.MyProcessingSketch

raptortech97 · Accepted Answer · 2013-04-30 00:15:22Z

0

Your classpath currently only contains location/of/core/core.jar, and not MyProcessingSketch.class. You should do java -cp location/of/core/core.jar;. MyProcessingSketch to include the current directory.

answered Apr 30, 2013 at 0:15

raptortech97

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