Reflection

package Reflection;

import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;

class Demo{
    
}

interface China {
    public static final String name = "Rollen";
    public static int age = 20;

    public void sayChina();

    public void sayHello(String name, int age);
}

class Person implements China{
    
    /*must have a none parameter constructor*/
    public Person(){
        
    }
    
    public Person(String name, int age){
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "[" + this.name + "  " + this.age + "]";
    }

    private String name;
    private int age;
    @Override
    public void sayChina() {
        // TODO Auto-generated method stub
        
    }

    @Override
    public void sayHello(String name, int age) {
        // TODO Auto-generated method stub
        
    }
}


public class Reflection {
    
    public static void main(String[] args) {
        /**
         * for class Demo
         */
        Demo demo = new Demo();
        System.out.println(demo.getClass().getName());
        Class<?> demo1 = null;
        Class<?> demo2 = null;
        Class<?> demo3 = null;
        try {
            demo1 = Class.forName("Reflection.Demo");
            demo2 = new Demo().getClass();
            demo3 = Demo.class;
        } catch (ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        System.out.println(demo1.getSimpleName()+"  "+demo2.getName()+"  "+demo3.getName());
        
        
        /**
         * For class Person
         */
        Class<?> person = Person.class;
        Person p = null;
        try {
            p = (Person)person.newInstance();
        } catch (InstantiationException | IllegalAccessException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }        
        p.setName("Kelvin");
        p.setAge(24);
        System.out.println(p.toString());
        
        Class<?> ps = new Person().getClass();
        Constructor<?>[] cons = ps.getConstructors();
        for(int i = 0;i< cons.length;i++){
            int modifier = cons[i].getModifiers();
            
            System.out.println("constructor:"+ cons[i] );
            System.out.println("constructor:"+Modifier.toString(modifier)+" "+ cons[i] );
        }
        try {
            Person p1 = (Person) cons[0].newInstance();
            System.out.println(p1.toString());
            Person p2 = (Person) cons[1].newInstance("summer",22);
            System.out.println(p2.toString());
            Class<?>[] ifs = p2.getClass().getInterfaces();
            System.out.println(ifs[0].getSimpleName());
            
            Person p3 = (Person) cons[2].newInstance();
            Person p4 = (Person) cons[3].newInstance();
        } catch (InstantiationException | IllegalAccessException
                | IllegalArgumentException | InvocationTargetException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        
        /**
         * To get all methods in Person
         */
        Method[] methods = new Person().getClass().getMethods();
        for(int i =0;i < methods.length;i++){
            System.out.println(methods[i].getName());
        }
        
        try {
            Method method = new Person().getClass().getMethod("setName", String.class);
            Person pm = new Person();
            try {
                method.invoke(pm, "jean");
                System.out.println(pm.toString());
            } catch (IllegalAccessException | IllegalArgumentException
                    | InvocationTargetException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        } catch (NoSuchMethodException | SecurityException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        
    }
    
}