Here you can find the source of isPrimitiveWrapper(Class clazz)
public static boolean isPrimitiveWrapper(Class clazz)
//package com.java2s; /**//from www. j a v a 2 s . co m * JLibs: Common Utilities for Java * Copyright (C) 2009 Santhosh Kumar T <santhosh.tekuri@gmail.com> * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2.1 of the License, or (at your option) any later version. * * This library 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 * Lesser General Public License for more details. */ import java.util.HashMap; public class Main { private static final HashMap<Class, Class> PRIMITIVES = new HashMap<Class, Class>(); public static boolean isPrimitiveWrapper(Class clazz) { return PRIMITIVES.containsKey(clazz); } }