Getting java.lang.NoClassDefFoundError when trying the execute a java.class

Question

I created the following class located in the MainJPrint.java file

import com.XXXXX.pdfPrint.PDFPrint;

public class MainJPrint
{
   public static void main(String[] args) 
    { 
        //System.out.println("Hello World!"); 
        print(".....");
    }   
    public static String print (final String url)
    {
        Object rc = AccessController.doPrivileged(new java.security.PrivilegedAction() 
        {
            public Object run()
            {
                 ...
            }
         }
    }
}

In the same folder I have a jar archive jPrint.jar I compile the class using the following command

>javac -classpath jPrint.jar MainJPrint.java

When I'm trying to execute resulted class file, I get this error:

>java MainJPrint    

 java.lang.NoClassDefFoundError: com/XXXXX/pdfPrint/PDFPrint

If I uncomment the Hello World line and comment the next line, the program runs fine.

I'm using j2sdk1.4.2 installed at C:\j2sdk1.4.2. I do also have installed other java versions (at C:\Program Files\Java: jre 1.6.0_01, jre 1.6.0_02, j2re1.4.2, jre6, jre7, jdk1.7.0_03)

The PATH variable contains the C:\j2sdk1.4.2\bin path, however I think the java.exe is loaded from the upper version, but it shouldn't matter and I can call it like

>C:\j2sdk1.4.2\bin\java.exe MainJPrint

jPrint.jar is a third party archive and I need to create an applet which exposes a method so I can call it with javascript. I'm not a java developer, I'm having some little troubles and I'm really on an end here.

I tried other options like:

>java MainJPrint -cp .
>java MainJPrint -cp jPrint.jar

So how can I execute that class file which uses a class located in a separate archive?

Did you try java -cp jPrint.jar MainJPrint? The class argument is usually placed last. — adarshr
– adarshr, Commented May 4, 2012 at 12:03
@TimBüthe, the third party company recommends to create that applet using this version. — Adrian Iftode
– Adrian Iftode, Commented May 4, 2012 at 12:20

RTBarnard · Accepted Answer · 2012-05-04 12:58:13Z

1

To execute a class that depends on external JARs, you need to specify all elements of the classpath on the command line.

If you don't specify a classpath, Java automatically uses . (the current directory), which is why, if MainJPrint didn't depend on jPrint.jar, your invocation java MainJPrint would have worked.

But when you specify -cp jPrint.jar, Java does NOT automatically add the current directory to the classpath, which means that it then cannot find MainJPrint. You need to specify both. On Mac/*nix, the following invocation should work:

java -cp jPrint.jar:. MainJPrint

Or on Windows:

java -cp jPrint.jar;. MainJPrint

edited May 4, 2012 at 12:58

answered May 4, 2012 at 12:16

RTBarnard

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6 Comments

Adrian Iftode Over a year ago

I'm getting Error: Could not find or load main class MainJPrint

Adrian Iftode Over a year ago

MainJPrint is my class, is not located in the jar, that jar is a third party one

RTBarnard Over a year ago

Are you certain that you're executing that exact command from within a folder that contains both jPrint.jar and the compiled MainJPrint.class files? You could try reversing the order of the classpath: java -cp .:jPrint.jar MainJPrint in case there's some quirk of circumstance going on...

RTBarnard Over a year ago

This is unexpected behavior, and I've just been able to verify the accuracy of my suggestion with several versions of Java on a couple of platforms. For thoroughness, can you edit your question to include the output of each of the following commands, executed in sequence (assuming you're on Windows based on the > prompt): dir, javac -cp jPrint.jar MainJPrint.java, dir, java -cp . MainJPrint, java -cp jPrint.jar:. MainJPrint. It would also be helpful if, instead of an excerpt, you could edit MainJPrint to be a minimal example and post its complete code.

RTBarnard Over a year ago

Ah, if you are on Windows, then you should actually be separating the entries with a semicolon instead of a colon: java -cp jPrint.jar;. MainJPrint. It's been so many years since I've used Windows that I completely forgot.

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