fieldmodifierspy.java

java tutorial.sun公司官方出品。java入门书籍。最新版

/*
 * Copyright (c) 1995 - 2008 Sun Microsystems, Inc.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   - Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 *   - Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *
 *   - Neither the name of Sun Microsystems nor the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */ 

import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import static java.lang.System.out;

enum Spy { BLACK , WHITE }

public class FieldModifierSpy {
    volatile int share;
    int instance;
    class Inner {}

    public static void main(String... args) {
	try {
	    Class<?> c = Class.forName(args[0]);
	    int searchMods = 0x0;
	    for (int i = 1; i < args.length; i++) {
		searchMods |= modifierFromString(args[i]);
	    }

	    Field[] flds = c.getDeclaredFields();
	    out.format("Fields in Class '%s' containing modifiers:  %s%n",
		       c.getName(),
		       Modifier.toString(searchMods));
	    boolean found = false;
	    for (Field f : flds) {
		int foundMods = f.getModifiers();
		// Require all of the requested modifiers to be present
		if ((foundMods & searchMods) == searchMods) {
		    out.format("%-8s [ synthetic=%-5b enum_constant=%-5b ]%n",
			       f.getName(), f.isSynthetic(),
			       f.isEnumConstant());
		    found = true;
		}
	    }

	    if (!found) {
		out.format("No matching fields%n");
	    }

        // production code should handle this exception more gracefully
	} catch (ClassNotFoundException x) {
	    x.printStackTrace();
	}
    }

    private static int modifierFromString(String s) {
	int m = 0x0;
	if ("public".equals(s))           m |= Modifier.PUBLIC;
	else if ("protected".equals(s))   m |= Modifier.PROTECTED;
	else if ("private".equals(s))     m |= Modifier.PRIVATE;
	else if ("static".equals(s))      m |= Modifier.STATIC;
	else if ("final".equals(s))       m |= Modifier.FINAL;
	else if ("transient".equals(s))   m |= Modifier.TRANSIENT;
	else if ("volatile".equals(s))    m |= Modifier.VOLATILE;
	return m;
    }
}