Reflection in Java

package reflection;

import java.lang.annotation.Annotation;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Parameter;

public class Main {

    public static void main(String[] args) throws ClassNotFoundException {
        // Returns the Class object associated with the class or interface with the
        // given string name.
        Class<?> clazz = Class.forName("reflection.Employee");

        printConstructors(clazz);
        printMethods(clazz);
        printClasses(clazz);
        printAnnotations(clazz);
    }

    private static void printConstructors(Class<?> clazz) {
        System.out.println("======== Constructor API ========");

        Constructor<?>[] constructors = clazz.getDeclaredConstructors();
        for (Constructor<?> constructor : constructors) {
            System.out.println("Constructor Name: " + constructor.getName());
            System.out.println("Constructor Parameter Count: " + constructor.getParameterCount());

            Parameter[] parameters = constructor.getParameters();
            for (Parameter parameter : parameters) {
                System.out.println("Constructor's parameter: " + parameter);
            }
        }
        // 通过反射创建对象
        System.out.println("New instance using reflection");
        Constructor<?> cons;
        try {
            cons = clazz.getConstructor(int.class,double.class);
            Employee employee = (Employee) cons.newInstance(1, 2.3);
            System.out.println(employee);
        } catch (NoSuchMethodException | SecurityException | InstantiationException | IllegalAccessException | IllegalArgumentException | InvocationTargetException e) {
            e.printStackTrace();
        }

        System.out.println("======== Constructor API END ========\n");
    }

    private static void printMethods(Class<?> c) {
        System.out.println("======== Method API ========");

        Method[] methods = c.getDeclaredMethods();
        System.out.println("Number of methods: " + methods.length);

        for (Method method : methods) {
            System.out.println("Method name: " + method.getName());
            System.out.println("Method return type: " + method.getReturnType().getName());
            System.out.println("Method parameter count: " + method.getParameterCount());

            Parameter[] parameters = method.getParameters();
            for (Parameter parameter : parameters) {
                System.out.println("Method's Parameter: " + parameter);
            }
        }
        // Invoke method
        System.out.println("Invoke method using reflection");
        try {
            Method method = c.getMethod("getSalary");
            System.out.println("Method return value: " + method.invoke(new Employee()));
        } catch (NoSuchMethodException | SecurityException | IllegalAccessException | IllegalArgumentException
                | InvocationTargetException e) {
            e.printStackTrace();
        }

        System.out.println("======== Method API END ========\n");
    }

    private static void printClasses(Class<?> c) {
        System.out.println("======== Class API ========");

        Class<?>[] classes = c.getDeclaredClasses();
        for (Class<?> class1 : classes) {
            System.out.println("Class: " + class1.getName());
        }

        System.out.println("======== Class API END ========\n");
    }

    private static void printAnnotations(Class<?> c) {
        System.out.println("======== Annotation API ========");

        // 获取类上的注解
        Annotation[] classAnnotations = c.getDeclaredAnnotations();
        for (Annotation annotation : classAnnotations) {
            System.out.println("Class Annotation: " + annotation);
        }

        // 获取方法上的注解
        Method[] methods = c.getDeclaredMethods();
        for (Method method : methods) {
            Annotation[] methodAnnotations = method.getDeclaredAnnotations();
            for (Annotation annotation : methodAnnotations) {
                System.out.println("Method Annotation: " + annotation);
            }
        }

        // 获取构造器上的注解
        Constructor<?>[] constructors = c.getDeclaredConstructors();
        for (Constructor<?> constructor : constructors) {
            Annotation[] constructorAnnotations = constructor.getDeclaredAnnotations();
            for (Annotation annotation : constructorAnnotations) {
                System.out.println("Constructor Annotation: " + annotation);
            }
        }

        System.out.println("======== Annotation API END ========\n");
    }
}