Here you can find the source of isNimbusLookAndFeel()
public static final boolean isNimbusLookAndFeel()
//package com.java2s; import javax.swing.UIManager; public class Main { /** The Nimbus look and feel name */ public static final String NIMBUS = "Nimbus"; /**//w w w .ja v a 2 s. c o m * Returns true if the Nimbus look and feel is used. * @return boolean */ public static final boolean isNimbusLookAndFeel() { return NIMBUS.equalsIgnoreCase(UIManager.getLookAndFeel().getName()); } }