ReflectionTest.java Source code

Introduction

Here is the source code for ReflectionTest.java

Source

/*
   This program is a part of the companion code for Core Java 8th ed.
   (http://horstmann.com/corejava)
    
   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.
    
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
    
   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.Scanner;

/**
 * This program uses reflection to print all features of a class.
 * @version 1.1 2004-02-21
 * @author Cay Horstmann
 */
public class ReflectionTest {
    public static void main(String[] args) {
        // read class name from command line args or user input
        String name;
        if (args.length > 0)
            name = args[0];
        else {
            Scanner in = new Scanner(System.in);
            System.out.println("Enter class name (e.g. java.util.Date): ");
            name = in.next();
        }

        try {
            // print class name and superclass name (if != Object)
            Class cl = Class.forName(name);
            Class supercl = cl.getSuperclass();
            String modifiers = Modifier.toString(cl.getModifiers());
            if (modifiers.length() > 0)
                System.out.print(modifiers + " ");
            System.out.print("class " + name);
            if (supercl != null && supercl != Object.class)
                System.out.print(" extends " + supercl.getName());

            System.out.print("\n{\n");
            printConstructors(cl);
            System.out.println();
            printMethods(cl);
            System.out.println();
            printFields(cl);
            System.out.println("}");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
        System.exit(0);
    }

    /**
     * Prints all constructors of a class
     * @param cl a class
     */
    public static void printConstructors(Class cl) {
        Constructor[] constructors = cl.getDeclaredConstructors();

        for (Constructor c : constructors) {
            String name = c.getName();
            System.out.print("   ");
            String modifiers = Modifier.toString(c.getModifiers());
            if (modifiers.length() > 0)
                System.out.print(modifiers + " ");
            System.out.print(name + "(");

            // print parameter types
            Class[] paramTypes = c.getParameterTypes();
            for (int j = 0; j < paramTypes.length; j++) {
                if (j > 0)
                    System.out.print(", ");
                System.out.print(paramTypes[j].getName());
            }
            System.out.println(");");
        }
    }

    /**
     * Prints all methods of a class
     * @param cl a class
     */
    public static void printMethods(Class cl) {
        Method[] methods = cl.getDeclaredMethods();

        for (Method m : methods) {
            Class retType = m.getReturnType();
            String name = m.getName();

            System.out.print("   ");
            // print modifiers, return type and method name
            String modifiers = Modifier.toString(m.getModifiers());
            if (modifiers.length() > 0)
                System.out.print(modifiers + " ");
            System.out.print(retType.getName() + " " + name + "(");

            // print parameter types
            Class[] paramTypes = m.getParameterTypes();
            for (int j = 0; j < paramTypes.length; j++) {
                if (j > 0)
                    System.out.print(", ");
                System.out.print(paramTypes[j].getName());
            }
            System.out.println(");");
        }
    }

    /**
     * Prints all fields of a class
     * @param cl a class
     */
    public static void printFields(Class cl) {
        Field[] fields = cl.getDeclaredFields();

        for (Field f : fields) {
            Class type = f.getType();
            String name = f.getName();
            System.out.print("   ");
            String modifiers = Modifier.toString(f.getModifiers());
            if (modifiers.length() > 0)
                System.out.print(modifiers + " ");
            System.out.println(type.getName() + " " + name + ";");
        }
    }
}