反射Reflect(Java基础篇)（三）

    @Test
    public  void fun6()throws Exception{
   Class clazz=Class.forName("itheima.com.Person");
    //Person p = (Person) clazz.newInstance();
        //公共的成员变量
    Field[] fields = clazz.getFields();
    for(Field field:fields){
        System.out.println(field);
        //public int itheima.com.Person.age
    }
    //所有的成员变量
     Field[] declaredFields = clazz.getDeclaredFields();
    for(Field field2:declaredFields){
        System.out.println(field2);
        //private java.lang.String itheima.com.Person.name
        //public int itheima.com.Person.age
    }
    System.out.println("-------");
    //获取一个成员变量
    Field ageField = clazz.getField("age");
    System.out.println(ageField);//public int itheima.com.Person.age
    //创建对象
    Constructor con = clazz.getConstructor();
    Object p = con.newInstance();
    //void set(Object obj,Object value):将指定对象参数中由此Field对象表示的字段设置为指定的新值
    ageField.set(p,11);
    System.out.println(p);//Person{name='null', age=11}
    }

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 + '\'' +
                '}';
    }
}

/*
     练习：通过反射实现如下操作
        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();
 */
public class ReflectDemo02 {
    public static void main(String[] args) throws ClassNotFoundException, NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {
        //获取Class对象
        Class<?> c = Class.forName("com.itheima_02.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: com.itheima_02.Student.function()
        Method m4 = c.getDeclaredMethod("function");
        m4.setAccessible(true);
        m4.invoke(obj);
    }
}

public class ReflectTest01 {
    public static void main(String[] args) throws NoSuchMethodException, InvocationTargetException, IllegalAccessException {
        //创建集合
        ArrayList<Integer> array = new ArrayList<Integer>();
//        array.add(10);
//        array.add(20);
//        array.add("hello");
        Class<? extends ArrayList> aClass = array.getClass();
        Method m1=aClass.getMethod("add",Object.class);
        m1.invoke(array,"hello");
        m1.invoke(array,"world");
        System.out.println(array);
    }
}

public class ReflectTest02 {
    public static void main(String[] args) throws IOException, ClassNotFoundException, NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {
        //把文件中的数据通过Io流读取,读取后放入集合中
        Properties prop = new Properties();
        //FileReader fr = new FileReader("myReflect\\class.txt");
        FileReader fr = new FileReader("myReflect\\class.properties");
        prop.load(fr);
        fr.close();
        //获取到类名和方法名
        String className = prop.getProperty("className");
        String methodName = prop.getProperty("methodName");
        //通过反射来使用
        Class<?> c = Class.forName(className);//com.itheima_06.Student
        Constructor<?> con = c.getConstructor();
        Object obj = con.newInstance();
        Method m = c.getMethod(methodName);//study
        m.invoke(obj);
    }
}