Constructor get and invoke with newInstance() - Java Reflection

Java examples for Reflection:Constructor

  1. HOME
  2. Java
  3. Reflection
  4. Constructor

Description

Constructor get and invoke with newInstance()

Demo Code

import java.io.Console;
import java.nio.charset.Charset;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import static java.lang.System.out;

public class ConsoleCharset {
    public static void main(String... args) {
        Constructor[] ctors = Console.class.getDeclaredConstructors();
        Constructor ctor = null;//  ww  w.  ja va 2s . c  om
        for (int i = 0; i < ctors.length; i++) {
            ctor = ctors[i];
            if (ctor.getGenericParameterTypes().length == 0)
                break;
        }

        try {
            ctor.setAccessible(true);
            Console c = (Console) ctor.newInstance();
            Field f = c.getClass().getDeclaredField("cs");
            f.setAccessible(true);
            out.format("Console charset         :  %s%n", f.get(c));
            out.format("Charset.defaultCharset():  %s%n",
                    Charset.defaultCharset());

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

Result


Related Tutorials