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Close an external windows program using JNA Tag(s): JNA


This example will close a running Powerpoint. The idea is to scan the Windows titles and find a match. If found then the Windows message WinUser.WM_CLOSE is sent to the process using its handle. 

import com.sun.jna.platform.win32.User32;

import com.sun.jna.platform.win32.WinUser;

import com.sun.jna.platform.win32.WinDef.HWND;



// https://github.com/twall/jna#readme

//    you need 2 jars : jna-3.5.1.jar and platform-3.5.1.jar



public class KillMyPP {

  public static void main(String[] args) {

     HWND hwnd = User32.INSTANCE.FindWindow

       (null, "Microsoft PowerPoint - [Présentation1]"); // window title

                                                         // you need to modify this

                                                         // for your need

     if (hwnd == null) {

       System.out.println("PPT is not running");

     }

     else{

       User32.INSTANCE.PostMessage(hwnd, WinUser.WM_CLOSE, null, null);  // can be WM_QUIT in some occasion

     }

  }

}
You can make the search more precise by specifying the class name as the first parameter. You find the class name of a specific Windows program with a special utility program like Spy++ or the free alternative WinID. For PowerPoint, the class name is PP12FrameClass. 

        HWND hwnd = User32.INSTANCE.FindWindow

             ("PP12FrameClass", "Microsoft PowerPoint - [Présentation1]"); // class name and window title
You can search by the Windows title only, the class name only or with both.

To close Notepad 


        HWND hwnd = User32.INSTANCE.FindWindow

             ("Notepad", null); // class name

        ...

        User32.INSTANCE.PostMessage(hwnd, WinUser.WM_CLOSE, null, null);
If there is a document to be saved you be prompted. To avoid that and discard the current document use the WM_QUIT message instead of WM_CLOSE. 

        User32.INSTANCE.PostMessage(hwnd, WinUser.WM_QUIT, null, null);
If you want to kill all running instances, then you can loop until no handle is retrieved. 

import com.sun.jna.platform.win32.User32;

import com.sun.jna.platform.win32.WinUser;

import com.sun.jna.platform.win32.WinDef.HWND;



// https://github.com/twall/jna#readme

//    you need 2 jars : jna-3.5.1.jar and platform-3.5.1.jar



public class KillAllNotepad {

  public static void main(String[] args) {

    for (;;) {

        HWND hwnd = User32.INSTANCE.FindWindow

          ("Notepad", null); // class name

        if (hwnd == null) {

           System.out.println("No Notepad instance detected");

           break;

        }

        else{

           System.out.println("Notepad instance found.");

           User32.INSTANCE.PostMessage(hwnd, WinUser.WM_QUIT, null, null);

        }

     }

  }

}

See also this Howto