Using JNA for accessing tooltip from windows

i am started experimenting with JNA to access every tooltip from windows. For this i am sending TTM_GETTOOLINFO message continuously to window. Below is my code...

public class Test {

     public interface User32 extends StdCallLibrary {
     User32 INSTANCE = (User32) Native.loadLibrary("user32", User32.class);
     HWND GetForegroundWindow();  // add this
     int SendMessageA(HWND hwnd, int msg, int num1, TOOLINFO f );
    // int SendMessageW(HWND hwnd, int msg, int num1, TOOLINFO f );
   }


    public class TOOLINFO extends Structure
    {
        public int      cbSize;
        public int      uFlags;
        public HWND      hwnd;
        public UINT_PTR  uId;
        public RECT      rect;
        public HINSTANCE hinst;
        public char []    lpszText;

        TOOLINFO()
        {
            lpszText = new char[512];
        }
    }

    public static void main(String[] args)
    {
        new Test().go();
    }

    public void go()
    {
        TOOLINFO tt = new TOOLINFO();
        int WM_USER = 0x0400;
        HWND hwnd ;
        int i=0;
        while(true)
        {
            hwnd= User32.INSTANCE.GetForegroundWindow();
            try
            {
                i=User32.INSTANCE.SendMessageA(hwnd,WM_USER+8, 0, tt);
            }
            catch(Exception ex)
            {
               ex.printStackTrace();
            }
        if(i!=0)
            System.out.println("Tooltip :"+tt.lpszText);
                }
    }
}

But its not working. I am using window 8. I found two version of commctrl.h on web. One is showing that TTM_GETTOOLINFOA= WM_USER+8 TTM_GETTOOLINFOW= WM_USER+53 and other is showing TTM_GETTOOLINFOA= WM_USER+9 TTM_GETTOOLINFOW= WM_USER+54. However i tried with every combination with both SendMessageA and W. So i think there are some fundamental mistakes. So anyone can plz help me in the same. Accessing tooltip from JNA.

public class JnaTest2 {

      public interface User32 extends StdCallLibrary {
      User32 INSTANCE = (User32) Native.loadLibrary("user32", User32.class);
      HWND GetForegroundWindow();  // add this
      int SendMessageW(HWND hwnd,int msg ,WPARAM w,TOOLINFOW lparam);
  }
    public class TOOLINFOW extends Structure
    {
        public int      cbSize;
        public int      uFlags;
        public HWND      hwnd;
        public UINT_PTR  uId;
        public RECT      rect;
        public HINSTANCE hinst;
        public Pointer pszText = new Memory(512);
        LPARAM l;
        Pointer lpReserved=null;
    }
public static void main(String[] args)
{

    new JnaTest2().go();
}
public void go()
{
    int WM_USER = 0x0400;
    TOOLINFOW tt = new TOOLINFOW();
    tt.cbSize=tt.size();
    System.out.println(tt.size());
    HWND hwnd ;
    int j=0;
    while(true)
    {
        hwnd=User32.INSTANCE.GetForegroundWindow();
        tt.hwnd=hwnd;
        try
        {
            j=User32.INSTANCE.SendMessageW(hwnd,WM_USER+53,new WPARAM(0),tt);
        }
        catch(Exception ex)
        {
           ex.printStackTrace();
        }
        if(j!=0)
            System.out.println("Tooltip :"+tt.pszText.getString(0));

    }
}

}