从静态字段中检索值（不属于特定对象）

/*==================================================================================================

 RoboLib - An Expansion and Improvement Library for WPILibJ

 Copyright (C) 2015  Matthew Crocco


 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.


 You should have received a copy of the GNU Lesser General Public

 License along with this library; if not, write to the Free Software

 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA

 =================================================================================================*//**来 自 NowJava.com - 时  代  Java**/

import java.lang.reflect.Array;

import java.lang.reflect.Constructor;

import java.lang.reflect.Field;

import java.lang.reflect.InvocationTargetException;

import java.lang.reflect.Method;


public class Main{

    /**

     * Retrieve Value from Static Field (Belonging to No Particular

     * Object)

     *

     * @param klass           Containing Class

     * @param fieldName       Name of Filed

     * @param conversionClass Class to Convert Result To (prevents Type Mismatch)

     * @return Value of Static Field of type 'conversionClass'

     */

    public static <T> T getStaticField(Class<?> klass, String fieldName,

            Class<T> conversionClass) {

        conversionClass = (Class<T>) ensureClassNotPrimitive(conversionClass);
/*来自 nowjava - 时  代  Java*/

        try {

            return conversionClass.cast(retrieveField(

                    klass.getDeclaredField(fieldName), null));

        } catch (final Exception e) {

            if (klass.getSuperclass() == null)

                throw new RuntimeReflectionException(

                        "Failure to reflectively obtain Static Field '"

                                + fieldName + "'!", e);

        }


        return getStaticField(klass.getSuperclass(), fieldName,

                conversionClass);

    }

    /**

     * Returns either this class if it is not a Primitive Class or the Object Class of this Primitive

     * Class. e.g. Integer.class for int.class and Double.class for double.class. <br />

     * <br />

     * The Primitive Class is that value returned by {@link Class#getPrimitiveClass(String)}.

     *

     * @param klass

     * @return

     */

    private static Class<?> ensureClassNotPrimitive(Class<?> klass) {

        if (klass == byte.class)

            return Byte.class;

        else if (klass == short.class)

            return Short.class;

        else if (klass == int.class)

            return Integer.class;

        else if (klass == long.class)

            return Long.class;

        else if (klass == float.class)

            return Float.class;

        else if (klass == double.class)