Utils : Kill and Force-Stop functions for android app.

RootUtils.java

public class RootUtils {

    private static Process su;

    public static void gainRoot() {
        try {
            su = Runtime.getRuntime().exec("su");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }


    public static void forceStop(String packageName) {
        try {
            DataOutputStream stream = new DataOutputStream(su.getOutputStream());

            stream.writeBytes("adb shell" + "\n");
            stream.flush();

            stream.writeBytes("am force-stop " + packageName + "\n");
            stream.flush();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    
    public static void captureScreen(String path) {
        DataOutputStream os = new DataOutputStream(su.getOutputStream());

        try {
            os.writeBytes("adb shell" + "\n");
            os.flush();

            os.writeBytes("screencap -p " + path + ".png\n");
            os.flush();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static void kill(String packageName) {
        try {
            DataOutputStream stream = new DataOutputStream(su.getOutputStream());

            stream.writeBytes("adb shell" + "\n");
            stream.flush();

            stream.writeBytes("am kill " + packageName + "\n");
            stream.flush();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    
    public static boolean isRooted() {
        boolean retval = false;
        Process suProcess;

        try {
            if (su == null) {
                su = Runtime.getRuntime().exec("su");
            }

            DataOutputStream os = new DataOutputStream(su.getOutputStream());
            DataInputStream osRes = new DataInputStream(su.getInputStream());

            if (null != os && null != osRes) {
                // Getting the id of the current user to check if this is root
                os.writeBytes("id\n");
                os.flush();

                String currUid = osRes.readLine();

                if (null == currUid) {
                    retval = false;
                    Log.d("ROOT", "Can't get root access or denied by user");
                } else if (currUid.contains("uid=0")) {
                    retval = true;
                    Log.d("ROOT", "Root access granted");
                } else {
                    retval = false;
                    Log.d("ROOT", "Root access rejected: " + currUid);
                }
            }
        } catch (Exception e) {
            // Can't get root !
            // Probably broken pipe exception on trying to write to output stream (os) after su failed, meaning that the device is not rooted

            retval = false;
            Log.d("ROOT", "Root access rejected [" + e.getClass().getName() + "] : " + e.getMessage());
        }

        return retval;
    }
}

Thanks for sharing this. I want to draw your attention that this part is not reliable:

 public static boolean isRooted() {
        boolean retval = false;
        Process suProcess;

        try {
            if (su == null) {
                su = Runtime.getRuntime().exec("su"); // this, I had to take it out of *if* condition i.e. to re-acquire the runtime always.
            }
...
}