Java之反射--练习

﹏ヽ暗。殇╰゛Y 2022-06-16 04:50 203阅读 0赞

**定义Student 类**：包含：姓名和年龄等属性，有参和无参构造方法，输出所有信息的方法

1.使用多种方法生成一个Student类的Class对象  
2.使用Class类获取Student类的结构信息并输出  
3.通过有参(无参)构造方法动态创建Student类的对象  
4.使用反射修改和查询Student类的姓名属性  
5.使用反射动态执行Student类输出信息的方法

--------------------

**代码：**

**Student类**

package 敲代码;
    //定义Student 类，包含：姓名和年龄等属性，有参和无参构造方法，输出所有信息的方法
    
    
    public class Student {
        private String name;
        private int age;
        private String sex;
    
        @Override
        public String toString() {
            return "Student [name=" + name + ", age=" + age + ", sex=" + sex + "]";
        }
        public Student(){}
        public Student(String name,int age,String sex){
            this.name=name;
            this.age=age;
            this.sex=sex;
        }
        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;
        }
    
        public String getSex() {
            return sex;
        }
    
        public void setSex(String sex) {
            this.sex = sex;
        }
    
        public void eat(){
            System.out.println("eat apple!");
        }
    
        private void run(){
            System.out.println("run and listen to music!");
        }
    
        public static void play(){
            System.out.println("play game");
        }
    
    }

--------------------

测试类：

package 敲代码;
    
    import java.lang.reflect.Constructor;
    import java.lang.reflect.Field;
    import java.lang.reflect.InvocationTargetException;
    import java.lang.reflect.Method;
    
    
    public class Test {
        public static void main(String[] args) {
            //1.获取类对象
            //first
            Student student=new Student();
            Class clazz=student.getClass();
            System.out.println(clazz.hashCode());
            //second
            Class clazz2=Student.class;
            System.out.println(clazz2.hashCode());
            //third
            try {
                Class clazz3=Class.forName("敲代码.Student");
                System.out.println(clazz3.hashCode());
            } catch (ClassNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
    
    
            //2.使用Class类获取Student类的结构信息并输出
            try {
                //构造方法
                Constructor[] constructors=clazz.getDeclaredConstructors();
                for (Constructor constructor2 : constructors) {
                    System.out.println(constructor2);
                }
    
                //获取方法对象
                Method[] methods=clazz.getDeclaredMethods();
                for (Method method : methods) {
                    System.out.println(method);
                }
    
                //获取属性
                Field[] fields=clazz.getDeclaredFields();
                for (Field field : fields) {
                    System.out.println(field);
                }
            } catch (SecurityException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
    
            //3.通过有参(无参)构造方法动态创建Student类的对象
            try {
                Constructor<Student> constructor=clazz2.getConstructor(String.class,int.class,String.class);
                Student student2=constructor.newInstance("张三",18,"张三");
                System.out.println(student2);
    
    
                //4.使用反射修改和查询Student类的姓名属性
                student2.setName("李四");
                System.out.println(student2.getName());
    
                //5.使用反射动态执行Student类输出信息的方法
                Method method=clazz.getMethod("eat", null);
                method.invoke(student, null);
            } catch (NoSuchMethodException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (SecurityException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (InstantiationException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IllegalAccessException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IllegalArgumentException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (InvocationTargetException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }   
        }
    }

--------------------

**运行结果：**

![这里写图片描述][SouthEast]  
![这里写图片描述][SouthEast 1]

[SouthEast]: /images/20220616/213da20267394524bd284db2ccf2c6f7.png
[SouthEast 1]: /images/20220616/d09566004a6c44b586b31fc4a5e7c80f.png