Thread: Writing Path name to configure Java

Originally Posted by PhHein

Because there's an order what the compiler checks. First all required dependencies are checked, and if those are ok, the actual code is compiled. In this case the compiler didn't get to that point.

Ok, thanks. I'd prefer to find why I can't get the Ptolemy.plot package to be found before I worry about getting the code to actually work. I don't know what else to try though - everything you have said makes sense, I just cannot get it to work.

Copy my example from reply #19 exactly in your system and make it work.

If it doesn't, copy your input and output here.

Input:

package ph;
 
import ptolemy.plot.*;
 
public class PLTest{
	public static void main(String[] args){
		System.out.println("Jap");
		Plot p = new Plot();
		p.setName("phh");
		System.out.println(p.getName());
	}
}

And in the command terminal: javac -classpath .;C:/ProgramFiles/Java/jdk1.7.0_21/ptplot5.8/ptolemy/plot/plot.jar PLTest.java
3 errors: Cannot find ptolemy.plot package
and two more errors - cannot find symbol Plot

Then the jar file is not in that directory: C:/ProgramFiles/Java/jdk1.7.0_21/ptplot5.8/ptolemy/plot/

Originally Posted by PhHein

Then the jar file is not in that directory: C:/ProgramFiles/Java/jdk1.7.0_21/ptplot5.8/ptolemy/plot/

I am not sure I understand. I see a plot 'executible JAR file' in the file folder plot but I also see the file folder 'plotml' in 'plot' which contains the 'executible JAR file' plotml

Dammit, post the complete path to plot.jar. I bet it is not: C:/ProgramFiles/Java/jdk1.7.0_21/ptplot5.8/ptolemy/plot/

Originally Posted by PhHein

Dammit, post the complete path to plot.jar. I bet it is not: C:/ProgramFiles/Java/jdk1.7.0_21/ptplot5.8/ptolemy/plot/

No, it is C:/ProgramFiles/Java/jdk1.7.0_21/ptplot5.8/ptolemy/plot/plot.jar

Ok, last try. Create a new folder c:/plot and copy the plot.jar into it and try again with javac -classpath .;c:/plot/plot.jar PLTest.java. If that doesn't work I'm lost.

Originally Posted by PhHein

Ok, last try. Create a new folder c:/plot and copy the plot.jar into it and try again with javac -classpath .;c:/plot/plot.jar PLTest.java. If that doesn't work I'm lost.

That didn't work either. I'll try again later, although I would not be sure what else to try. I did not think it would take so long to just configure this package and all of the tutorials I have looked at are too vague for my tastes. Many thanks for all your efforts though, I appreciate it.

Hi PhHein,
I managed to finally get the code to compile and I fixed the code to correct the remaining errors as you anticipated. I went to run it using the command:
java -cp .;"C:\Program Files\Java....\plot.jar" Edisc and the following message appears: (I have typed what it says since I don't know how to copy from the terminal)

Exception in thread "main" java.lang.NoClassDefFoundError: ptolemy/util/RunnableExceptionCatcher
at ptolemy.plot.Plot.addPoint(Plot.java:275)
at Edisc.main(Edisc.java:38)
Caused by java.lang.ClassNotFoundException: ptolemy.util.RunnableExceptionCatcher
at java.net.URLClassLoader$1.run(Unknown Source)
at java.net.URLClassLocader$1.run(Unknown Source)
.... (some more statements similar to the above) then ...2 more.

I can't make any sense out of that - so given that everything compiled fine, there must be an error somewhere during runtime.

Have you any thoughts?

Originally Posted by CAF

I fixed the code

Please post the modified version of the code any time you make changes

Hi jps,

Originally Posted by jps

Please post the modified version of the code any time you make changes

Yes, sure here it is:

 
import java.io.Console;
import java.io.*;
import java.lang.Math;
import java.lang.Boolean;
import ptolemy.plot.*;
 
public class Edisc {
	public static void main (String args[]) {
 
	Console myConsole = System.console();
 
	Plot disc = new Plot();
	disc.setTitle("Graph of the axial E field from a charged disc");
	disc.setXLabel("distance along z");
	disc.setYLabel("E field");
 
	PlotFrame myFrame = new PlotFrame("E vs z", disc);
	myFrame.setSize(800,600);
 
	int dataSet = 0;
 
	double q = 6.0e-9;
	double R  = 10;
	double eps = 8.85e-12;
 
 
 
	int points = 100;
 
	double E[] = new double[points];
	double z[] = new double[points];
 
	for(int i = 0; i < (points-1); i++) {
	z[i] = (100*(int)i/points); 
 
	double Eqn = q/((2*(Math.PI)*eps*(Math.pow(R,2)))*(1 - z[i]/(Math.sqrt((Math.pow(R,2)) + (Math.pow(z[i],2))))));
 
	disc.addPoint(dataSet, z[i], Eqn, true);
 
	myFrame.setVisible(true);
	}
 
} 
 
}

This version of the code compiled, it is just at runtime I get errors. (I did not know that at runtime you could possibly have more errors, so I am a bit mystified). Thanks.

the posted code is not the problem

Where is the Plot and PlotFrame class?

It is much easier to assist with a SSCCE

Originally Posted by jps

Where is the Plot and PlotFrame class?

Yes, I forgot to reference the other jar file - it now works albeit my graph looks a bit strange (but I should be able to fix this via changing the plotframe size etc..) Everytime I run though and when it produces the graph, I lose control of the command terminal, that is I cannot type anything in it anymore. This means everytime I run (after making changes), I must first get to correct directory, then compile then run. This is tedious. Is there a way to regain access of the terminal? Thanks again.

It sounds like an infinite loop or the thread is blocked.

This is where a debugger comes in handy, but it can still be done without one. Either way, you will just have to figure out where the program execution stops (for what ever reason it may be).

I just want to mention also, as a side note on errors.
Treat the program like it has exactly one error at all times. Until you correct the first error listed, there are no other errors. Every time you attempt to compile, and eventually run, stop and fix the "only" error there is and try to compile and run again. Compile and run often.

Originally Posted by jps

It sounds like an infinite loop or the thread is blocked.

Can you see anywhere in my code where I created an infinite loop?

Originally Posted by CAF

Can you see anywhere in my code where I created an infinite loop?

There is only one loop in the posted code, use a println and test it

Originally Posted by jps

There is only one loop in the posted code, use a println and test it

When I put in a println statement, I have the contents of that statement displayed a large number of times in the command terminal, so I think that the loop is going over and over again. Is there a way to fix this?
EDIT: At the end of the code, I put the statement 'System.exit(0);' which ends the infinite loop and I can regain access of the terminal. I was wondering though, why do I have an infinite loop and where can I fix it in the code?

Originally Posted by CAF

When I put in a println statement

Always include the modified version of the code when changes are made.

Originally Posted by CAF

At the end of the code, I put the statement 'System.exit(0);' which ends the infinite loop

infinite loops do not end, that is what is so special about them. Again, post the code showing the changes so we can see what is happening.

Originally Posted by CAF

why do I have an infinite loop

Are you sure you do? Include the index counter of the loop in your println to see how many times it does run since you are using such a large number during testing (unless you would like to count them all).

Here is the updated code:

import java.io.Console;
import java.io.*;
import java.lang.Math;
import java.lang.Boolean;
import ptolemy.plot.*;
 
public class Edisc1 {
	public static void main (String args[]) {
 
	Console myConsole = System.console();
 
	Plot disc = new Plot();
	disc.setTitle("Graph of the axial E field from a charged disc");
	disc.setXLabel("distance along z");
	disc.setYLabel("E field");
 
	PlotFrame myFrame = new PlotFrame("E vs z", disc);
	myFrame.setSize(10,20);
 
	int dataSet = 0;
 
	double q = 6.0e-6;
	double R  = 10;
	double eps = 8.85e-12;
 
 
 
	int points = 500;
 
	double E[] = new double[points];
	double z[] = new double[points];
 
	for(int i = 0; i < (points-1); i++) {
	z[i] = (100*(int)i/points); 
 
	double Eqn = (q/((2*(Math.PI)*eps*(Math.pow(R,2))))*(1 - (z[i]/(Math.sqrt((Math.pow(R,2)) + (Math.pow(z[i],2)))))));
 
	disc.addPoint(dataSet, z[i], Eqn, true);
 
	System.out.println("Graph created");
 
	myFrame.setVisible(true);
	}
 
	System.exit(0);
 
} 
 
}

The only thing I have changed since last time is the insertion of the println and System.exit(0) statements at the very end

setting the frame visible 500 times is a bit silly, no?

Originally Posted by PhHein

setting the frame visible 500 times is a bit silly, no?

I thought the 500 I set was the number of points that would be plotted on the graph (obviously this is not the case). For some reason, when I run the program now, the graph instantaneously appears then dissapears. Any ideas why this would be the case?

Also, the number of times 'Graph created' appears seems to be proportional to what I set int points = ... to be. I don't understand this either.

When you try to compile what? How could something appear when compiling?

Originally Posted by PhHein

When you try to compile what? How could something appear when compiling?

Ah you're too quick! I edited my post when I reread it. See above

Originally Posted by CAF

The only thing I have changed

It may seem simple and unimportant from your seat, but from the chair where your screen is not visible, it is important to post the code any time any change is made to the syntax. "Always" post the modified code so we can see what changed where. See below:

Originally Posted by CAF

System.exit(0) statements at the very end

The fact that the System.exit was placed OUTSIDE the loop, means that the loop is NOT an infinite loop, and that it is exiting as expected.

--- Update ---

Originally Posted by CAF

Also, the number of times 'Graph created' appears seems to be proportional to what I set int points = ... to be. I don't understand this either.

Every line of code from:
for(int i = 0; i < (points-1); i++) {
all the way down to the next:
}
will be executed every time the loop runs. In the posted code that would include the 5 lines following the for statement, which includes the println, and the setVisible(true).
The system.exit is outside the loop and is only executed once, after the loop exits. This is the place where you would put things that should only happen once, after the loop exits. (like the set visible)