public interface duang {
	public String getClazzName();
}

public class classA implements duang{
	@Override
	public String getClazzName() {
		return "A類"+this.getClass().getName();
	}

}
 

public class classD {
    
    public static void main(String[] args)
    {
//        System.out.println(classA.getClazzName());
        try {
            Class clazz = Class.forName("classA");
            duang duang = (duang) clazz.newInstance();
            System.out.println(duang.getClazzName());
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }
    }
}
 

public class classB implements duang{
	@Override
	public String getClazzName() {
		return "B類"+this.getClass().getName();
	}
}

Class clazz = Class.forName("classA");

Class clazz = Class.forName("classB");