public void quit() {
        int pid = android.os.Process.myPid();
        android.os.Process.killProcess(pid);
        System.exit(0);
    }

Intent i= new Intent(getapplicationcontext,TARGETACTIVITY.class);
finish();
startActivity(intent);

public void close()
               {
             Intent intent = new Intent(Intent.ACTION_MAIN);
             intent.addCategory(Intent.CATEGORY_HOME);
             intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
             startActivity(intent);
               }

System.exit();

try{
-------
-----
----
}
Catch (Exception e)
{
exception.printStackTrace();//using alert box to show your exception.
finish(); //use this one of your Application it will close the application.
}

Intent intent = new Intent(Intent.ACTION_MAIN);
             intent.addCategory(Intent.CATEGORY_HOME);
             intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
             startActivity(intent);