Java-反射综合练习

ReflectDemo:

package com.fluffysponge;

import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Properties;

/**
 *      反射获取构造方法并使用练习1:
 *      通过反射实现如下的操作：
 *      Student s = new Student("林青霞",30,"西安");
 *      System.out.println(s);
 *
 *      反射获取构造方法并使用练习2:
 *      通过反射实现如下的操作：
 *      Student s = new Student("林青霞");
 *      System.out.println(s);
 * --------------------------------------------------------
 *      反射获取成员变量并使用练习:
 *      通过反射实现如下的操作：
 *      Student s = new Student("");
 *      s.name = "林青霞";
 *      s.age = 30;
 *      s.address = "西安";
 *      System.out.println(s);
 *  ---------------------------------------------------------
 *      反射获取成员方法并使用练习:
 *      通过反射实现如下的操作：
 *      Student s = new Student("");
 *      s.method1();
 *      s.method2("林青霞");
 *      String ss = s.method3("林青霞",30);
 *      System.out.println(ss);
 *      s.function();
 *  ----------------------------------------------------------
 *      反射练习：越过泛型检查
 *      我有一个ArrayList<Integer>集合，现在想在这个集合中添加一个字符串数据，如何实现？
 *
 *      反射练习：通过配置文件运行类中的方法
 */


public class ReflectDemo {
//    //反射获取构造方法并使用练习1:
//    public static void main(String[] args) throws ClassNotFoundException, NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {
//        //获取Class对象
//        Class<?> c = Class.forName("com.fluffysponge.Student");
//
//        //public Student(String name, int age, String address)
//        //Constructor<T> getConstructor(Class<?>... parameterTypes)
//        Constructor<?> con = c.getConstructor(String.class, int.class, String.class);
//        //基本数据类型也可以通过.class得到对应的class类型
//
//        //T newInstance(Object... initargs)
//        Object obj = con.newInstance("林青霞", 30, "西安");
//        System.out.println(obj);
//    }

//    //反射获取构造方法并使用练习2:
//    public static void main(String[] args) throws ClassNotFoundException, NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {
//        //获取Class对象
//        Class<?> c = Class.forName("com.fluffysponge.Student");
//
//        //private Student(String name)
//        //Constructor<T> getDeclaredConstructor(Class<?>... parameterTypes)
//        Constructor<?> con = c.getDeclaredConstructor(String.class);
//
//        //暴力反射，私有的构造方法不能常规newInstance，需要取消访问检查
//        //public void setAccessible(boolean flag):值为true,取消访问检查
//        con.setAccessible(true);
//
//        Object obj = con.newInstance("林青霞");
//        System.out.println(obj);
//    }

//    //反射获取成员变量并使用练习:
//    public static void main(String[] args) throws ClassNotFoundException, NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException, NoSuchFieldException {
//        //获取Class对象
//        Class<?> c = Class.forName("com.fluffysponge.Student");
//
//        //Student s = new Student("");
//        Constructor<?> con = c.getConstructor();
//        Object obj = con.newInstance();
//        System.out.println(obj);
//
//        //s.name = "林青霞";
//        //Field nameField = c.getField("name");//NoSuchFieldException
//        Field nameField = c.getDeclaredField("name");//IllegalAccessException
//        nameField.setAccessible(true);
//        nameField.set(obj,"林青霞");
//        System.out.println(obj);
//
//        //s.age = 30;
//        Field ageField = c.getDeclaredField("age");
//        ageField.setAccessible(true);
//        ageField.set(obj,30);
//        System.out.println(obj);
//
//        //s.address = "西安";
//        Field addressField = c.getDeclaredField("address");
//        addressField.setAccessible(true);
//        addressField.set(obj,"西安");
//        System.out.println(obj);
//    }

//    //反射获取成员方法并使用练习:
//    public static void main(String[] args) throws ClassNotFoundException, NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {
//        //获取Class对象
//        Class<?> c = Class.forName("com.fluffysponge.Student");
//
//        //Student s = new Student("");
//        Constructor<?> con = c.getConstructor();
//        Object obj = con.newInstance();
//
//        //s.method1();
//        Method m1 = c.getMethod("method1");
//        m1.invoke(obj);
//
//        //s.method2("林青霞");
//        Method m2 = c.getMethod("method2", String.class);
//        m2.invoke(obj,"林青霞");
//
//        //String ss = s.method3("林青霞",30);
//        //System.out.println(ss);
//        Method m3 = c.getMethod("method3", String.class, int.class);
//        Object o = m3.invoke(obj, "林青霞", 30);
//        System.out.println(o);
//
//        //s.function();
//        //Method m4 = c.getMethod("function");//NoSuchMethodException
//        Method m4 = c.getDeclaredMethod("function");
//        m4.setAccessible(true);
//        m4.invoke(obj);
//    }

//    //反射练习：越过泛型检查
//    public static void main(String[] args) throws NoSuchMethodException, InvocationTargetException, IllegalAccessException {
//        //创建集合
//        ArrayList<Integer> array = new ArrayList<>();
//
////        array.add(10);
////        array.add(20);
////        array.add("hello");
//
//        Class<? extends ArrayList> c = array.getClass();
//        Method m = c.getMethod("add", Object.class);
//        m.invoke(array, "hello");
//        m.invoke(array, "world");
//        m.invoke(array, "java");
//
//        System.out.println(array);
//    }

    //反射练习：通过配置文件运行类中的方法
    public static void main(String[] args) throws IOException, ClassNotFoundException, NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {
////        Cat cat = new Cat();
////        cat.miaomiao();
//
//        Dog dog = new Dog();
//        dog.wangwang();

        /**
         *  具体运行那个文件，在class.txt文件中配置
         *  className=xxx
         *  methodName=xxx
         */
        //加载数据
        Properties prop = new Properties();
        FileReader fr = new FileReader("MyReflect\\class.txt");
        prop.load(fr);
        fr.close();
        /*
        *   className=com.fluffysponge.Cat
            methodName=miaomiao
        * */
        String className = prop.getProperty("className");
        String methodName = prop.getProperty("methodName");

        //通过反射来使用
        Class<?> c = Class.forName(className);//com.fluffysponge.Cat
        Constructor<?> con = c.getConstructor();
        Object obj = con.newInstance();

        Method m = c.getMethod(methodName);//miaomiao
        m.invoke(obj);
    }
}

Student:

package com.fluffysponge;

public class Student {
    //成员变量：一个私有，一个默认，一个公共
    private String name;
    int age;
    public String address;

    //构造方法：一个私有，一个默认，两个公共

    public Student() {
    }

    private Student(String name) {
        this.name = name;
    }

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

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

    //成员方法：一个私有，四个公共
    private void function(){
        System.out.println("function");
    }

    public void method1(){
        System.out.println("method");
    }

    public void method2(String s){
        System.out.println("method:" + s);
    }

    public String method3(String s,int i){
        return s + "," + i;
    }

    @Override
    public String toString() {
        return "Student{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", address='" + address + '\'' +
                '}';
    }
}

Cat:

package com.fluffysponge;

public class Cat {
    public void miaomiao(){
        System.out.println("小猫喵喵叫");
    }
}

Dog:

package com.fluffysponge;

public class Dog {
    public void wangwang(){
        System.out.println("小狗汪汪叫");
    }
}

class.txt:

className=com.fluffysponge.Cat
methodName=miaomiao