java反射_demo

https://blog.youkuaiyun.com/stonesing/article/details/52358288

package Interview;

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

//https://blog.youkuaiyun.com/stonesing/article/details/52358288
//一个person父类
class Person {
	private int age;
	private String name;

	public Person() {

	}

	public Person(int age, String name) {
		this.age = age;
		this.name = name;
	}

	public int getAge() {
		return age;
	}

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

	public String getName() {
		return name;
	}

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

}

// 一个接口
interface ActionInterface {
	public void walk(int m);
}

// 超人子类实现接口
class Superman extends Person implements ActionInterface {
	private boolean BlueBriefs;

	public void fly() {
		System.out.println("超人会飞耶～～");
	}

	public void setBlueBriefs(boolean blueBriefs) {
		BlueBriefs = blueBriefs;
	}

	@Override
	public void walk(int m) {
		// TODO Auto-generated method stub
		System.out.println("超人会走耶～～走了" + m + "米就走不动了！");
	}

}

public class reflect_demo {

	public static void main(String[] args) throws Exception {
		// TODO Auto-generated method stub
		demo1();
		System.out.println("===============================================");
		demo2();
		System.out.println("===============================================");
		demo3();
		System.out.println("===============================================");
		demo4();
		System.out.println("===============================================");
		demo5();
		System.out.println("===============================================");
		demo6();
		System.out.println("===============================================");
		demo7();
		System.out.println("===============================================");
		demo8();
	}

	public static void demo1() {
		Person person = new Person();
		System.out.println(
				"Demo1: 包名: " + person.getClass().getPackage().getName() + " 完整类名：" + person.getClass().getName());
	}

	// 能通过反射得到类
	public static void demo2() throws ClassNotFoundException {
		// 定义两个类型都未知的Class , 设置初值为null, 看看如何给它们赋值成Person类
		Class<?> class1 = null;
		Class<?> class2 = null;

		// 写法1, 可能抛出 ClassNotFoundException
		// Class.forName
		class1 = Class.forName("Interview.Person");
		System.out.println("Demo2:(写法1) 包名: " + class1.getPackage().getName() + "，" + "完整类名: " + class1.getName());

		// 写法2
		class2 = Person.class;
		System.out.println("Demo2:(写法2) 包名: " + class2.getPackage().getName() + "，" + "完整类名: " + class2.getName());
	}

	// 通过Java反射机制，用Class 创建类对象
	public static void demo3() throws ClassNotFoundException, IllegalAccessException, InstantiationException {
		Class<?> class1 = null;
		class1 = Class.forName("Interview.Person");
		// 得到实例
		Person person = (Person) class1.newInstance();
		person.setName("aa");
		person.setAge(3);
		System.out.println("Demo3: " + person.getName() + " : " + person.getAge());

	}

	// 通过反射得到一个类的构造函数
	public static void demo4() throws ClassNotFoundException, IllegalArgumentException, InstantiationException,
			IllegalAccessException, InvocationTargetException {
		Class<?> class1 = null;
		Person person1 = null;
		Person person2 = null;

		class1 = Class.forName("Interview.Person");
		// 得到构造函数的集合
		Constructor<?>[] constructors = class1.getConstructors();

		person1 = (Person) constructors[0].newInstance();
		person1.setAge(30);
		person1.setName("zhangsan");

		person2 = (Person) constructors[1].newInstance(20, "lisi");

		System.out.println("Demo4: " + person1.getName() + " : " + person1.getAge() + "  ,   " + person2.getName()
				+ " : " + person2.getAge());

	}

	// 通过Java反射机制操作成员变量, set 和 get
	public static void demo5() throws IllegalArgumentException, IllegalAccessException, SecurityException,
			NoSuchFieldException, InstantiationException, ClassNotFoundException {
		Class<?> class1 = null;
		class1 = Class.forName("Interview.Person");

		Object obj = class1.newInstance();
		Field personNameField = class1.getDeclaredField("name");
		personNameField.setAccessible(true);
		personNameField.set(obj, "wangwu");
		System.out.println("Demo5: 修改属性之后得到属性变量的值：" + personNameField.get(obj));

	}

	// 通过Java反射机制得到类的一些属性： 继承的接口，父类，函数信息，成员信息，类型等
	public static void demo6() throws ClassNotFoundException {
		Class<?> class1 = null;
		class1 = Class.forName("Interview.Superman");

		// 取得父类名称
		Class<?> superClass = class1.getSuperclass();
		System.out.println("Demo6:  SuperMan类的父类名: " + superClass.getName());

		Field[] fields = class1.getDeclaredFields();
		for (int i = 0; i < fields.length; i++) {
			System.out.println("类中的成员:" + fields[i]);
		}

		// 取得类方法
		Method[] methods = class1.getDeclaredMethods();
		for (int i = 0; i < methods.length; i++) {
			System.out.println("Demo6,取得SuperMan类的方法：");
			System.out.println("函数名：" + methods[i].getName());
			System.out.println("函数返回类型：" + methods[i].getReturnType());
			System.out.println("函数访问修饰符：" + Modifier.toString(methods[i].getModifiers()));
			System.out.println("函数代码写法： " + methods[i]);
		}
		// 取得类实现的接口,因为接口类也属于Class,所以得到接口中的方法也是一样的方法得到哈
		Class<?> interfaces[] = class1.getInterfaces();
		for (int i = 0; i < interfaces.length; i++) {
			System.out.println("实现的接口类名: " + interfaces[i].getName());
		}

	}

	// Demo7: 通过Java反射机制调用类方法
	public static void demo7() throws ClassNotFoundException, SecurityException, NoSuchMethodException,
			IllegalArgumentException, IllegalAccessException, InvocationTargetException, InstantiationException {
		Class<?> class1 = null;
		class1 = Class.forName("Interview.Superman");

		System.out.println("Demo7: \n调用无参方法fly()：");
		Method method = class1.getMethod("fly");
		method.invoke(class1.newInstance());

		System.out.println("调用有参方法walk(int m)：");
		method = class1.getMethod("walk", int.class);
		method.invoke(class1.newInstance(), 100);
	}

	// Demo8: 通过Java反射机制得到类加载器信息
	public static void demo8() throws ClassNotFoundException {
		Class<?> class1 = null;
		class1 = Class.forName("Interview.Superman");
		String nameString = class1.getClassLoader().getClass().getName();

		System.out.println("Demo8: 类加载器类名: " + nameString);
	}

}

运行结果：

Demo1: 包名: Interview 完整类名：Interview.Person

===============================================

Demo2:(写法1) 包名: Interview，完整类名: Interview.Person

Demo2:(写法2) 包名: Interview，完整类名: Interview.Person

===============================================

Demo3: aa : 3

===============================================

Demo4: zhangsan : 30  ,   lisi : 20

===============================================

Demo5: 修改属性之后得到属性变量的值：wangwu

===============================================

Demo6:  SuperMan类的父类名: Interview.Person

类中的成员:private boolean Interview.Superman.BlueBriefs

Demo6,取得SuperMan类的方法：

函数名：fly

函数返回类型：void

函数访问修饰符：public

函数代码写法： public void Interview.Superman.fly()

Demo6,取得SuperMan类的方法：

函数名：walk

函数返回类型：void

函数访问修饰符：public

函数代码写法： public void Interview.Superman.walk(int)

Demo6,取得SuperMan类的方法：

函数名：setBlueBriefs

函数返回类型：void

函数访问修饰符：public

函数代码写法： public void Interview.Superman.setBlueBriefs(boolean)

实现的接口类名: Interview.ActionInterface

===============================================

Demo7:

调用无参方法fly()：

超人会飞耶～～

调用有参方法walk(int m)：

超人会走耶～～走了100米就走不动了！

===============================================

Demo8: 类加载器类名: sun.misc.Launcher$AppClassLoader