JNA example program java.lang.NoClassDefFoundError

Question

I can compile this JNA example code (from step 2 of https://github.com/twall/jna/#getting_started): ``` package com.sun.jna.examples; import com.sun.jna.Library; import com.sun.jna.Native; import com.sun.jna.Platform; /** Simple example of JNA interface mapping and usage. */ public class HelloWorld { // This is the standard, stable way of mapping, which supports extensive // customization and mapping of Java to native types. public interface CLibrary extends Library { CLibrary INSTANCE = (CLibrary) Native.loadLibrary((Platform.isWindows() ? "msvcrt" : "c"), CLibrary.class); void printf(String format, Object... args); } public static void main(String[] args) { CLibrary.INSTANCE.printf("Hello, World
"); for (int i=0;i < args.length;i++) { CLibrary.INSTANCE.printf("Argument %d: %s
", i, args[i]); } } } ``` ...using `javac -classpath .:jna.jar -g HelloWorld.java` without error. (I downloaded jna.jar and put it in the same directory as HelloWorld.java for now.) But when I run it using `j…

Accepted Answer

This example (as well as vast majority of java classes) uses packages:

```
package com.sun.jna.examples;
```

In order to compile / run it properly you need to run javac / java from the "root" folder (e.g. folder where "com" is located):

Let's say you have a folder called `examples`. You'd put both the `jna.jar` and the source code in it preserving folder structure:

```
/examples
 jna.jar
 /com
   /sun
      /jna
         /examples
           HelloWorld.java
```

You compile and run using:

```
javac -classpath .:jna.jar -g com/sun/jna/examples/HelloWorld.java

java -classpath .:jna.jar com.sun.jna.examples.HelloWorld
```

Note the path separators in the former case and dots in the latter.

JNA example program java.lang.NoClassDefFoundError

Solution

Problem