calling dll function java

I would recommend Java Native Access (JNA) as its easier than using JNI.
Please find an example (from Wikipedia):

import com.sun.jna.Library;
import com.sun.jna.Native;

/** Simple example of Windows native library declaration and usage. */
public class BeepExampl{
   public interface Kernel32 extends Library {
       // FREQUENCY is expressed in hertz and ranges from 37 to 32767
       // DURATION is expressed in milliseconds
       public boolean Beep(int FREQUENCY, int DURATION);
       public void Sleep(int DURATION);
   }
   public static void main(String[] args) {
    Kernel32 lib = (Kernel32) Native.loadLibrary("kernel32", 
           Kernel32.class);
    lib.Beep(698, 500);
    lib.Sleep(500);
    lib.Beep(698, 500);
   }
}

Lets say you have a DLL with some functions,
Create an java interface which has the same method signatures as the functions in DLL.
For example

public interface NativeExample{

  public int method1(String param1);
  public boolean mehthod2();

}

Now following is the way you load the DLL (assuming its name is NativeLib.dll)

NativeExample nativeExample= (NativeExample)Native.loadLibrary("NativeLib", NativeExample.class);

Once you have this, you can call the method from the DLL via java methods.

`nativeExample.method("test");`
`nativeExample.method2();`