java.lang.UnsatisfiedLinkError dll.HelloJNI.sayHello()V

While calling a dll from java i was getting this error

Exception in thread "main" java.lang.UnsatisfiedLinkError: dll.HelloJNI.sayHello()V
at dll.HelloJNI.sayHello(Native Method)
at dll.HelloJNI.main(HelloJNI.java:7)

Here is my java code

 public class HelloJNI {  
 public static void main(String[] args) {
     HelloJNI h = new HelloJNI(); 
     h.sayHello();  // invoke the native method
   }

 static {
     try{
         System.load("D://Program Files//Java//jdk1.7.0_40//bin//hello.dll"); // hello.dll (Windows) or libhello.so (Unixes) 
     }
     catch (UnsatisfiedLinkError e) {
          System.err.println("Native code library failed to load.\n" + e);
          System.exit(1);
        }

   }
   private native void sayHello();

}

Here is my c code for dll.

am using gcc compiler to generate dll

for MinGWC am using

gcc -Wl,--add-stdcall-alias -I"\include" -I"\include\win32" -shared -o hello.dll HelloJNI.c

#include <jni.h>
#include <stdio.h>
#include "HelloJNI.h"

JNIEXPORT void JNICALL Java_HelloJNI_sayHello(JNIEnv *env, jobject thisObj) {
   printf("Hello World!\n");
   return;
}

I have remove the package dll and while executing i got this error

#
# A fatal error has been detected by the Java Runtime Environment:
#
#  EXCEPTION_ACCESS_VIOLATION (0xc0000005) at pc=0x610d70b4, pid=1720, tid=1160
#
# JRE version: Java(TM) SE Runtime Environment (7.0_40-b43) (build 1.7.0_40-b43)
# Java VM: Java HotSpot(TM) Client VM (24.0-b56 mixed mode, sharing windows-x86 )
# Problematic frame:
# C  [cygwin1.dll+0xd70b4]
#
# Failed to write core dump. Minidumps are not enabled by default on client versions of Windows
#
# If you would like to submit a bug report, please visit:
#   http://bugreport.sun.com/bugreport/crash.jsp
# The crash happened outside the Java Virtual Machine in native code.
# See problematic frame for where to report the bug.
#

You have added a package name since you generated the C code. The package name is now dll, but when you generated it, there wasn't one. Redo and adjust your C code accordingly so it agrees with the new .h file.