book.java

来自「java tutorial.sun公司官方出品。java入门书籍。最新版」· Java 代码 · 共 76 行

/*
 * Copyright (c) 1995 - 2008 Sun Microsystems, Inc.  All rights reserved.
 *
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 * modification, are permitted provided that the following conditions
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 *
 *   - Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
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 *   - Redistributions in binary form must reproduce the above copyright
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 *     documentation and/or other materials provided with the distribution.
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 *     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,
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 */ 

import java.lang.reflect.Field;
import java.util.Arrays;
import static java.lang.System.out;

enum Tweedle { DEE, DUM }

public class Book {
    public long chapters = 0;
    public String[] characters = { "Alice", "White Rabbit" };
    public Tweedle twin = Tweedle.DEE;

    public static void main(String... args) {
	Book book = new Book();
	String fmt = "%6S:  %-12s = %s%n";

	try {
	    Class<?> c = book.getClass();

	    Field chap = c.getDeclaredField("chapters");
	    out.format(fmt, "before", "chapters", book.chapters);
  	    chap.setLong(book, 12);
	    out.format(fmt, "after", "chapters", chap.getLong(book));

	    Field chars = c.getDeclaredField("characters");
	    out.format(fmt, "before", "characters",
		       Arrays.asList(book.characters));
	    String[] newChars = { "Queen", "King" };
	    chars.set(book, newChars);
	    out.format(fmt, "after", "characters",
		       Arrays.asList(book.characters));

	    Field t = c.getDeclaredField("twin");
	    out.format(fmt, "before", "twin", book.twin);
	    t.set(book, Tweedle.DUM);
	    out.format(fmt, "after", "twin", t.get(book));

        // production code should handle these exceptions more gracefully
	} catch (NoSuchFieldException x) {
	    x.printStackTrace();
	} catch (IllegalAccessException x) {
	    x.printStackTrace();
	}
    }
}