Get Constructor information using reflection - Java Reflection

Java examples for Reflection:Constructor

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

Description

Get Constructor information using reflection

Demo Code

import java.lang.reflect.*;
import java.util.function.*;
import static java.lang.System.out;
import java.lang.reflect.*;
import java.util.function.*;
import static java.lang.System.out;

class MethodParameterSpy {

    private static final String fmt = "%24s: %s%n";

    // for the morbidly curious
    <E extends RuntimeException> void genericThrow() throws E {
    }//w ww  .j a  v a 2s .co  m

    public static void printClassConstructors(Class c) {
        Constructor[] allConstructors = c.getConstructors();
        out.format(fmt, "Number of constructors", allConstructors.length);
        for (Constructor currentConstructor : allConstructors) {
            printConstructor(currentConstructor);
        }
        Constructor[] allDeclConst = c.getDeclaredConstructors();
        out.format(fmt, "Number of declared constructors",
                allDeclConst.length);
        for (Constructor currentDeclConst : allDeclConst) {
            printConstructor(currentDeclConst);
        }
    }

    public static void printClassMethods(Class c) {
        Method[] allMethods = c.getDeclaredMethods();
        out.format(fmt, "Number of methods", allMethods.length);
        for (Method m : allMethods) {
            printMethod(m);
        }
    }

    public static void printConstructor(Constructor c) {
        out.format("%s%n", c.toGenericString());
        Parameter[] params = c.getParameters();
        out.format(fmt, "Number of parameters", params.length);
        for (int i = 0; i < params.length; i++) {
            printParameter(params[i]);
        }
    }

    public static void printMethod(Method m) {
        out.format("%s%n", m.toGenericString());
        out.format(fmt, "Return type", m.getReturnType());
        out.format(fmt, "Generic return type", m.getGenericReturnType());

        Parameter[] params = m.getParameters();
        for (int i = 0; i < params.length; i++) {
            printParameter(params[i]);
        }
    }

    public static void printParameter(Parameter p) {
        out.format(fmt, "Parameter class", p.getType());
        out.format(fmt, "Parameter name", p.getName());
        out.format(fmt, "Modifiers", p.getModifiers());
        out.format(fmt, "Is implicit?", p.isImplicit());
        out.format(fmt, "Is name present?", p.isNamePresent());
        out.format(fmt, "Is synthetic?", p.isSynthetic());
    }

    public static void main(String... args) {

        try {
            printClassConstructors(Class.forName(args[0]));
            printClassMethods(Class.forName(args[0]));
        } catch (ClassNotFoundException x) {
            x.printStackTrace();
        }
    }
}
public class MethodParameterExamples {

    public class InnerClass {
    }

    enum Colors {
        RED, WHITE;
    }

    public static void main(String... args) {
        System.out.println("InnerClass:");
        MethodParameterSpy.printClassConstructors(InnerClass.class);

        System.out.println("enum Colors:");
        MethodParameterSpy.printClassConstructors(Colors.class);
        MethodParameterSpy.printClassMethods(Colors.class);
    }
}

/*
 * Copyright (c) 2013, 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