This is sample and best way for showing badge on notification launcher icon.
Add This Class in your application
public class BadgeUtils {
    public static void setBadge(Context context, int count) {
        setBadgeSamsung(context, count);
        setBadgeSony(context, count);
    }
    public static void clearBadge(Context context) {
        setBadgeSamsung(context, 0);
        clearBadgeSony(context);
    }
    private static void setBadgeSamsung(Context context, int count) {
        String launcherClassName = getLauncherClassName(context);
        if (launcherClassName == null) {
            return;
        }
        Intent intent = new Intent("android.intent.action.BADGE_COUNT_UPDATE");
        intent.putExtra("badge_count", count);
        intent.putExtra("badge_count_package_name", context.getPackageName());
        intent.putExtra("badge_count_class_name", launcherClassName);
        context.sendBroadcast(intent);
    }
    private static void setBadgeSony(Context context, int count) {
        String launcherClassName = getLauncherClassName(context);
        if (launcherClassName == null) {
            return;
        }
        Intent intent = new Intent();
        intent.setAction("com.sonyericsson.home.action.UPDATE_BADGE");
        intent.putExtra("com.sonyericsson.home.intent.extra.badge.ACTIVITY_NAME", launcherClassName);
        intent.putExtra("com.sonyericsson.home.intent.extra.badge.SHOW_MESSAGE", true);
        intent.putExtra("com.sonyericsson.home.intent.extra.badge.MESSAGE", String.valueOf(count));
        intent.putExtra("com.sonyericsson.home.intent.extra.badge.PACKAGE_NAME", context.getPackageName());
        context.sendBroadcast(intent);
    }
    private static void clearBadgeSony(Context context) {
        String launcherClassName = getLauncherClassName(context);
        if (launcherClassName == null) {
            return;
        }
        Intent intent = new Intent();
        intent.setAction("com.sonyericsson.home.action.UPDATE_BADGE");
        intent.putExtra("com.sonyericsson.home.intent.extra.badge.ACTIVITY_NAME", launcherClassName);
        intent.putExtra("com.sonyericsson.home.intent.extra.badge.SHOW_MESSAGE", false);
        intent.putExtra("com.sonyericsson.home.intent.extra.badge.MESSAGE", String.valueOf(0));
        intent.putExtra("com.sonyericsson.home.intent.extra.badge.PACKAGE_NAME", context.getPackageName());
        context.sendBroadcast(intent);
    }
    private static String getLauncherClassName(Context context) {
        PackageManager pm = context.getPackageManager();
        Intent intent = new Intent(Intent.ACTION_MAIN);
        intent.addCategory(Intent.CATEGORY_LAUNCHER);
        List<ResolveInfo> resolveInfos = pm.queryIntentActivities(intent, 0);
        for (ResolveInfo resolveInfo : resolveInfos) {
            String pkgName = resolveInfo.activityInfo.applicationInfo.packageName;
            if (pkgName.equalsIgnoreCase(context.getPackageName())) {
                String className = resolveInfo.activityInfo.name;
                return className;
            }
        }
        return null;
    }
}
==> MyGcmListenerService.java
Use BadgeUtils  class when notification comes.
public class MyGcmListenerService extends GcmListenerService { 
    private static final String TAG = "MyGcmListenerService"; 
    @Override
    public void onMessageReceived(String from, Bundle data) {
            String message = data.getString("Msg");
            String Type = data.getString("Type"); 
            Intent intent = new Intent(this, SplashActivity.class);
            intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
            PendingIntent pendingIntent = PendingIntent.getActivity(this, 0 /* Request code */, intent,
                    PendingIntent.FLAG_ONE_SHOT);
            Uri defaultSoundUri = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);
            NotificationCompat.BigTextStyle bigTextStyle= new NotificationCompat.BigTextStyle();
            bigTextStyle .setBigContentTitle(getString(R.string.app_name))
                    .bigText(message);
            NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(this)
                    .setSmallIcon(getNotificationIcon())
                    .setContentTitle(getString(R.string.app_name))
                    .setContentText(message)
                    .setStyle(bigTextStyle) 
                    .setAutoCancel(true)
                    .setSound(defaultSoundUri)
                    .setContentIntent(pendingIntent);
            int color = getResources().getColor(R.color.appColor);
            notificationBuilder.setColor(color);
            NotificationManager notificationManager =
                    (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
            int unOpenCount=AppUtill.getPreferenceInt("NOTICOUNT",this);
            unOpenCount=unOpenCount+1;
            AppUtill.savePreferenceLong("NOTICOUNT",unOpenCount,this);  
            notificationManager.notify(unOpenCount /* ID of notification */, notificationBuilder.build()); 
// This is for bladge on home icon          
        BadgeUtils.setBadge(MyGcmListenerService.this,(int)unOpenCount);
    }
    private int getNotificationIcon() {
        boolean useWhiteIcon = (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.LOLLIPOP);
        return useWhiteIcon ? R.drawable.notification_small_icon : R.drawable.icon_launcher;
    }
}
And clear notification from preference and also with badge count
 public class SplashActivity extends AppCompatActivity { 
                @Override
                protected void onCreate(Bundle savedInstanceState) {
                    super.onCreate(savedInstanceState);
                    setContentView(R.layout.activity_splash);
                    AppUtill.savePreferenceLong("NOTICOUNT",0,this);
                    BadgeUtils.clearBadge(this);
            }
    }
<uses-permission android:name="com.sonyericsson.home.permission.BROADCAST_BADGE" />