反射方式獲取成員變數並使用

Field物件

域（屬性，成員變數）物件，屬於java.base模組，java.lang.reflect包中

通過Class物件獲取屬性

getField(String name)

//返回一個Field物件，僅公共屬性

getDeclaredField(String name)

//返回一個Field物件，可獲取私有屬性

getDeclaredFields()

//返回此類所有（含私有）屬性的陣列

Field的常用方法

void set(Object obj,Object value)

//設定obj物件的指定屬性值為vlaue

void setAccessible(boolean flag)

//設定此屬性的可訪問性設定為指定布林值

Student.java

package Demo01;
​
import java.lang.reflect.Constructor;
​
​
/**
 * @author :K；
 */
public class Student {
    public String name;
    private int age;
    public Student() {
​
    }
    public Student(String name){
        System.out.println("輸入的姓名為："+name);
    }
    private Student(int age){
        System.out.println("你的年齡為："+age);
    }
    public void show(){
        System.out.println("我是公共的無參方法");
    }
    public  void show2(int a){
        System.out.println("我是公共的代參方法，你傳入的引數為："+a);
    }
    private  int show3(int a,int b){
        System.out.println("我是私有的代參方法");
        return a+b;
    }
​
    @Override
    public String toString() {
        return "Student{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

Reflect_GetField.java

package Demo01;

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;

public class Reflect_GetField {
    public static void main(String[] args) throws ClassNotFoundException, NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException, NoSuchFieldException {
        Class aClass = Class.forName("Demo01.Student");
        Constructor constructor = aClass.getConstructor();
        Student stu = (Student)constructor.newInstance();

        //Student stu =(Student)aClass.getConstructor().newInstance();  鏈式程式設計

        Field name = aClass.getField("name");
        name.set(stu,"小白白");

        Field age = aClass.getDeclaredField("age");
        age.setAccessible(true);
        age.set(stu,20);

        System.out.println(stu);
    }
}