Java 反射 (二) Class类

  //(1)传统new对象
          /*
          ClassLoader类
          public Class<?>LoadClass(String name)throws ClassNotFoundException{
              return loadclass(name,false);
          }
           */
          Cat cat = new Cat();
          //(2) 反射方式
          /*
            ClassLoader类，仍然是通过CLassLoader类加载Cat类的Class对象
            public Class<?>LoadClass(String name)throws CLassNotFoundException{
              return loadClass(name,false)
            }
           */
          Class cls1 = Class.forName("com.gbx.Cat");

  Class cls2 = Class.forName("com.gbx.Cat");
          System.out.println(cls1.hashCode()==cls2.hashCode());
          Class cls3 = Class.forName("com.gbx.reflection.Dog");
          System.out.println(cls3.hashCode()==cls2.hashCode());

/**
 * @author LeeZhi
 * @version 1.0
 * 演示Class类的常用方法
 */
public class Class02 {
    public static void main(String[] args) throws ClassNotFoundException, InstantiationException, IllegalAccessException, NoSuchFieldException {

        String classAllPath = "com.gbx.Car";
        //1.获取到Car类对应的Class对象
        //<?>表示不确定的Java类型
        Class<?>cls = Class.forName(classAllPath);
        //2.输出cls
        System.out.println(cls);//显示cls对象,是哪个类的Class对象  com.gbx.Car
        System.out.println(cls.getClass());//输出运行类型 java.lang.Class
        //3.得到包名
        System.out.println(cls.getPackage().getName());//包名
        //4,得到全类名
        System.out.println(cls.getName());
        //5.通过cls创建对象实例
        Car car =(Car)cls.newInstance();
        System.out.println(car);//car.toString()
        //6.通过反射获取属性 brand
        Field brand = cls.getField("brand");
        System.out.println(brand.get(car));
        //7.通过反射给属性赋值
        brand.set(car,"奔驰");
        System.out.println(brand.get(car));
        //8. 遍历得到所有属性
        Field[] fields = cls.getFields();
        System.out.println("===============");
        for (Field f:fields){
            System.out.println(f.getName());//名称
        }
    }
}

/**
 * @author LeeZhi
 * @version 1.0
 * 演示得到Class对象的各种方式(6)
 */
public class GetClass_ {

    public static void main(String[] args) throws ClassNotFoundException {

        //1. Class.forName
        String classAllPath = "com.gbx.Car";//通过读取配置文件获取
        Class<?>cls1 = Class.forName(classAllPath);
        System.out.println(cls1);

        //2.类名.class,应用场景用于参数传递
        Class<Car> cls2 = Car.class;
        System.out.println(cls2);

        //3. 对象.getClass()  应用场景,有对象实例
        Car car = new Car();
        Class cls3 = car.getClass();
        System.out.println(cls3);

        //4. 通过类加载器[4]来获取到类Class对象
        //(1)先得到类加载器 car
        ClassLoader classLoader = car.getClass().getClassLoader();
        //(2)通过类加载器得到class对象
        Class<?> cls4 = classLoader.loadClass(classAllPath);
        System.out.println(cls4);

        //cls1 , cls2 , cls3 , cls4其实是同一个对象
        System.out.println(cls1.hashCode()==cls2.hashCode());
        System.out.println(cls2.hashCode()==cls3.hashCode());
        System.out.println(cls3.hashCode()==cls4.hashCode());

        //5.基本数据(int,char,boolean,float,,double,byte,long,short)按如下方式得到Class类对象
        Class<Integer> integerClass = int.class;
        Class<Character>characterClass = char.class;
        Class<Boolean>booleanClass = boolean.class;
        System.out.println(integerClass);//int

        //6.基本数据类型对应的包装类，可以通过.type得到Class类对象
        Class<Integer>type1=Integer.TYPE;
        Class<Character>type2 = Character.TYPE;
        System.out.println(type1);

        System.out.println(integerClass.hashCode() == type1.hashCode());
    }
}

/**
 * @author LeeZhi
 * @version 1.0
 * 演示那些类型有Class对象
 */
public class AllTypeClass {
    public static void main(String[] args) {
        Class<String> cls1 = String.class;//外部类
        Class<Serializable> cls2 = Serializable.class;//接口
        Class<Integer[]> cls3 = Integer[].class;//数组
        Class<float[][]>cls4 = float[][].class;//二维数组
        Class<Deprecated>cls5 = Deprecated.class;//注释
        Class<Thread.State> cls6 = Thread.State.class;//枚举
        Class<Long>cls7 = long.class;//基本数据类型
        Class<Void>cls8 = void.class;//void数据类型
        Class<Class>cls9 = Class.class;
        System.out.println(cls1);
        System.out.println(cls2);
        System.out.println(cls3);
        System.out.println(cls4);
        System.out.println(cls5);
        System.out.println(cls6);
        System.out.println(cls7);
        System.out.println(cls8);
        System.out.println(cls9);

    }
}