ReflectionTest:由输入的类名得到类的信息

package reflection;

import java.lang.reflect.*;
import java.util.*;

public class ReflectionTest {
    public static void main(String[] args)
    {
        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
        {
            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);
    }
    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+"(");

            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(");");
        }
    }

    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("   ");
            String modifiers = Modifier.toString(m.getModifiers());
            if(modifiers.length()>0) System.out.print(modifiers+" ");//private static final都是修饰符
            System.out.print(retType.getName()+" "+name + "(");

            Class[] paramTypes = m.getParameterTypes();//获取一个方法的所有参数
            for(int j=0;j<paramTypes.length;j++)
            {
                if(j>0) System.out.print(", ");
                System.out.print(paramTypes[j].getName());//获取一个参数的类型
            }
            System.out.println(");");
        }
    }

    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 +";");

        }
    }

}