Java - NoClassDefFoundError

Question

I need to compile an external java file (say a.java). This is the code i wrote for the same.

(String path contains the path to the java and class file)

    command[0] = "javac";
    command[1] = path+"a.java";
    p = Runtime.getRuntime().exec(command);

The above code seems to work just fine. But the below code

    command[0] = "java";
    command[1] = "a";
    command[2] = "-cp";
    command[3] = "."+path+"a";
    p = Runtime.getRuntime().exec(command);        
    stdInput = new BufferedReader(new InputStreamReader(p.getInputStream()));
    stdError = new BufferedReader(new InputStreamReader(p.getErrorStream()));
    while ((temp = stdInput.readLine()) != null) result += "\n" + temp;
    while ((temp = stdError.readLine()) != null) result += "\n" + temp;

Causes the following error

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

Could someone explaine the problem with this code. Thanks !

Jon Skeet · Accepted Answer · 2013-01-20 17:00:57Z

4

You're specifying the class name first, and then the arguments for the classpath. The class name is always the last thing to come before the program-specific arguments. In your case, the classpath part will therefore not be treated as an option - it'll be considered as two arguments (-cp and the path) to the Java program itself.

So instead of:

java a -cp (whatever)

you want

java -cp (whatever) a

answered Jan 20, 2013 at 17:00

Jon Skeet

1.5m893 gold badges9.3k silver badges9.3k bronze badges

Sign up to request clarification or add additional context in comments.

6 Comments

Ankit Rustagi Over a year ago

I tried - command[0] = "java"; command[1] = "-cp"; command[2] = "."+path+"\\temp\\"; command[3] = "a"; But i'm still getting the same error. Is this command correct ?

Jon Skeet Over a year ago

@randomuser: Try running it from the command line first - it'll be a lot easier to experiment that way. Is the class file in the temp directory?

Ankit Rustagi Over a year ago

I get the same error when i run it using cmd, I found someone with same problem It seems a similar command worked for him.

Jon Skeet Over a year ago

@randomuser: That problem was due to putting the class filename rather than the class name. That's not your problem - I suspect your problem is that you're not compiling into the temp directory.

Ankit Rustagi Over a year ago

When working with cmd, when i change the current directory to the directory containing the .java file and the .class file, java a works just fine though. But when i explicitly try to avoid changing the current directory and try something like this java c:\\path_to_dir\\a I get the same error mentioned earlier.

|

Collectives™ on Stack Overflow

Java - NoClassDefFoundError

1 Answer 1

6 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

6 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related