Here you can find the source of isGTKLaF()
public static final boolean isGTKLaF()
//package com.java2s; /*//w w w . j ava 2 s .c o m * Copyright (C) 2008-2010 Igor Kriznar * * This file is part of GTD-Free. * * GTD-Free is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, either version 3 of the License, or * (at your option) any later version. * * GTD-Free is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with GTD-Free. If not, see <http://www.gnu.org/licenses/>. */ import javax.swing.UIManager; public class Main { private static Boolean gtklaf; public static final boolean isGTKLaF() { if (gtklaf == null) { try { gtklaf = Class.forName("com.sun.java.swing.plaf.gtk.GTKLookAndFeel") //$NON-NLS-1$ .isAssignableFrom(UIManager.getLookAndFeel().getClass()); } catch (Exception e) { gtklaf = Boolean.FALSE; } } return gtklaf; } }