Here you can find the source of isGTKLookAndFeel()
public static boolean isGTKLookAndFeel()
//package com.java2s; //License from project: Open Source License import javax.swing.UIManager; public class Main { /**/*from www .j ava2 s.c o m*/ * Determines if current L&F is GTKLookAndFeel */ public static boolean isGTKLookAndFeel() { // is current L&F some kind of GTKLookAndFeel? return UIManager.getLookAndFeel().getID().equals("GTK"); //NOI18N } }