Field get from class - Java Reflection

Java examples for Reflection:Field Get

  1. HOME
  2. Java
  3. Reflection
  4. Field Get

Description

Field get from class

Demo Code

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

enum Tweedle {//from  w w w  .j a  v a  2 s. c  o  m
    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();
        }
    }
}

/*
 * Copyright (c) 1995, 2008, Oracle and/or its affiliates. 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 Oracle or 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.
 */

Related Tutorials