Thread: Writing Path name to configure Java

The jar files you reference, have to be in the classpath. This is not a path issue.

Originally Posted by PhHein

The jar files you reference, have to be in the classpath. This is not a path issue.

Hi PhHein, could you give me an example of a typical class path? What I have is the following: \Program Files\Java\jdk1.7.0_21\bin. That's what I used to initially configure java. Should i make another classpath for Ptplot5.8 and/or where should I put this Ptplot5.8 file?

Thanks.

You have to add the path of all the included JARs to your classpath. You might find useful this tutorial.

And always keep in mind that path and classpath are two completely different things. Path is a system vartiable that tells your OS where to look for executables (java.exe etc.). Classpath is derfined at runtime and tells the compiler or VM where to look for java files (java, class, jar, etc.). Another link: How Classes are Found

Originally Posted by PhHein

And always keep in mind that path and classpath are two completely different things. Path is a system vartiable that tells your OS where to look for executables (java.exe etc.). Classpath is derfined at runtime and tells the compiler or VM where to look for java files (java, class, jar, etc.). Another link: How Classes are Found

What I have so far is java - classpath d:/tmp/ptplot5.8/ptolemy/plot/plot.jar. When I put this into the terminal, I get errors. I got this from one of the tutorials, however, I don't know what d:/tmp stands for, nor does the tutorial explain.

Thanks.

Replace it with the path to the jar file in your file system. It's just an example.

Hi PhHein,

Originally Posted by PhHein

Replace it with the path to the jar file in your file system. It's just an example.

That more or less is the same path - I think the problem is this /tmp. Do you know what that means and is it the error?

d:/tmp/ptplot5.8/ptolemy/plot/plot.jar is the path to the jar file in your file system. Drive d ,folder tmp, etc.

Originally Posted by PhHein

d:/tmp/ptplot5.8/ptolemy/plot/plot.jar is the path to the jar file in your file system. Drive d ,folder tmp, etc.

Hopefully that is the problem, I'll check later - thanks.

--- Update ---

Originally Posted by PhHein

d:/tmp/ptplot5.8/ptolemy/plot/plot.jar is the path to the jar file in your file system. Drive d ,folder tmp, etc.

So what I have is java -classpath C:\ProgramFiles\Java\jdk1.7.0_21\ptplot5.8\ptolemy \plot\plot.jar; and when compliling with the source: javac -classpath C:\ProgramFiles\Java\jdk1.7.0_21\ptplot5.8\plot\pl ot.jar; Edisc.java, where Edisc.java is the java file I want compiled. I still obtain the same error message that is ptolemy.plot package does not exist.

I am wondering if I need to provide a classpath for the other jar files (i.e I also see plotapplication.jar) If so, and this would be the next thing I try, do I put these different jar files in the same classpath. If so, how? and if not, how do I create another command in the terminal so as to write this other classpath before compiling?

Sorry if these are elementary questions: I am just starting out in JAVA and am installing the software onto my computer. I have done JAVA at my university, however, the problem I am having here is purely configuration (at the moment).

Many thanks.

You can add all jars at once when compiling, separated by semicolon: javac -classpath .;path1/jar1.jar;path2/jar2.jar Edisc.java
The . is the current directory, where your Edisc.java file is saved.

Originally Posted by PhHein

You can add all jars at once when compiling, separated by semicolon: javac -classpath .;path1/jar1.jar;path2/jar2.jar Edisc.java
The . is the current directory, where your Edisc.java file is saved.

So I have javac -classpath .;C:\ProgramFiles\Java\jdk1.7.0_21\ptplot5.8\ptole my\plot\plot.jar;C:\ProgramFiles.......\plot\plota pplication.jar;C:\ProgramFiles\.....\plotapplet.ja r Edisc.java

I still obtain the 'ptolemy.plot package does not exist' error. Is there anything else I could try? How do I know in advance what jar files to add to the classpath?

You have to add the jar that contains the package ptolemy.plot. It's in plot.jar.

Originally Posted by PhHein

You have to add the jar that contains the package ptolemy.plot. It's in plot.jar.

Something like javac -classpath .:C:\ProgramFilesJava\jdk1.7.0_21\ptplot5.8\ptolem y\plot\plot.jar ptolemy.plot?

javac -classpath .;C:/ProgramFilesJava/jdk1.7.0_21/ptplot5.8/ptolemy/plot/plot.jar Edisc.java

Originally Posted by PhHein

javac -classpath .;C:/ProgramFilesJava/jdk1.7.0_21/ptplot5.8/ptolemy/plot/plot.jar Edisc.java

Is that not what I tried in post #10?

Nope, it's not the same.

Originally Posted by PhHein

Nope, it's not the same.

I see - in post #10 I missed out \ptolemy\. That was just a typo. Is it not the same as in 12 then? (except I added on more jar files). When I enter what you wrote in 16, I still have this ptolemy.plot does not exist error.
Thanks for your patience.

Ok, I've slapped together a test:

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());
	}
}

Directories are:
d:/test.1/plot.jar
d:/test.2/ph/PLTest.java

D:\test.2>javac -classpath .;d:/test.1/plot.jar ph/PLTest.java
 
D:\test.2>java -cp .;d:/test.1/plot.jar ph/PLTest
Jap
phh
 
D:\test.2>

Compare that with what you have.

Here is my full source code:

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)*(1 - z[i]*((Math.sqrt((Math.pow(R,2)) + (Math.pow(z[i],2))))))^(-1);
 
	disc.addPoint(dataSet, z[i], Eqn, true);
 
	myFrame.setVisible(true);
	}
 
} 
 
}

You should first get rid of all the ptolemy stuff and compile it without it. You'll already run into compilation errors then.

Originally Posted by PhHein

You should first get rid of all the ptolemy stuff and compile it without it. You'll already run into compilation errors then.

Do you mean there are errors in the code?

Yes.

Originally Posted by PhHein

Yes.

All the errors that appeared were to do with this apparent non existence of the ptolemy.plot (there were 7 errors in total). Where are the other errors and why does the compiler not pick them up?

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.