java如何识别后台进程？

Question

    final List<WindowInfo> inflList=new ArrayList<WindowInfo>();

    final List<Integer> order=new ArrayList<Integer>();
    int top = User32.instance.GetTopWindow(0);
    while (top!=0)
    {
      order.add(top);
      top = User32.instance.GetWindow(top, User32.GW_HWNDNEXT);
    }
    User32.instance.EnumWindows(new WndEnumProc()
    {
    public boolean callback(int hWnd, int lParam)
    {
      if (User32.instance.IsWindowVisible(hWnd)) 
      {
        RECT r = new RECT();
        User32.instance.GetWindowRect(hWnd, r);
        if (r.left>-32000) 
        {     // minimized
            byte[] buffer = new byte[1024];
           User32.instance.GetWindowTextA(hWnd, buffer, buffer.length);

            String title = Native.toString(buffer);

            if (m.length == count)
        {
              // expand list
             m = Arrays.copyOf(m, m.length + arrayGrowth);
            }
            m[count]=Native.toString(buffer);
            System.out.println("title===="+m[count]);
            count++;
            inflList.add(new WindowInfo(hWnd, r, title));
        }

       }
       return true;
    }
    }, 0);

 Collections.sort(inflList, new Comparator<WindowInfo>()
 {
    public int compare(WindowInfo o1, WindowInfo o2)
    {
    return order.indexOf(o1.hwnd)-order.indexOf(o2.hwnd);
    }
 });
  for (WindowInfo w : inflList)
  {
     System.out.println(w);
  }

}
public static interface WndEnumProc extends StdCallLibrary.StdCallCallback
{
    boolean callback (int hWnd, int lParam);
}

public static interface User32 extends StdCallLibrary
{
    final User32 instance = (User32) Native.loadLibrary ("user32", User32.class);
    boolean EnumWindows (WndEnumProc wndenumproc, int lParam);
    boolean IsWindowVisible(int hWnd);
    int GetWindowRect(int hWnd, RECT r);
    void GetWindowTextA(int hWnd, byte[] buffer, int buflen);
    int GetTopWindow(int hWnd);
    int GetWindow(int hWnd, int flag);
    final int GW_HWNDNEXT = 2;
}

public static class RECT extends Structure 
{
    public int left,top,right,bottom;
}
public static class WindowInfo 
{
    int hwnd;
    RECT rect;
    String title;
    public WindowInfo(int hwnd, RECT rect, String title)
    {
        this.hwnd = hwnd; this.rect = rect; this.title = title;
    }
  public String toString()
  {
     return String.format("(%d,%d)-(%d,%d) : \"%s\"",
     rect.left ,rect.top,rect.right,rect.bottom,title);
  }
 }

它给出了输出：

(0,728)-(54,768) : "Start"

(0,728)-(1366,768) : ""

(0,0)-(0,0) : ""

(-8,-8)-(1374,736) : "Comp_Watch - NetBeans IDE 7.1.2"

(-8,-8)-(1374,736) : "how to identify background processes?? - Stack Overflow - Google Chrome"

(738,197)-(1338,447) : "Untitled - Notepad"

(0,0)-(1366,768) : "Program Manager"

我想知道为什么它在输出的第二行和第三行显示NULL？？他们是背景吗

过程？如何识别它们