我正在运行此代码,但是却收到此错误消息,无法解决。在反射的帮助下,要求使用工厂模式设计任何Java代码。在下面,我添加了我运行代码并再次输入文件名和类名TestReflectionFactoryDesign时出现的错误消息。
错误消息:
Exception in thread "main" java.lang.ClassNotFoundException: com.test.TestReflectionFactoryDesign.Student
at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:335)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:264)
at PersonFactory.getPersonWithFullQualifiedClassName(TestReflectionFactoryDesign.java:58)
at TestReflectionFactoryDesign.main(TestReflectionFactoryDesign.java:6)
代码:
public class TestReflectionFactoryDesign {
public static void main(String[] args) throws Exception {
Person student = PersonFactory.getPersonWithFullQualifiedClassName("com.test.TestReflectionFactoryDesign.Student");
student.say();
Person teacher = PersonFactory.getPersonWithClass(Teacher.class);
teacher.say();
Person student2 = PersonFactory.getPersonWithName("student");
student2.say();
}
}
class Student implements Person {
@Override
public void say() {
System.out.println("I am a student");
}
}
class Teacher implements Person {
@Override
public void say() {
System.out.println("I am a teacher");
}
}
interface Person {
void say();
}
class PersonFactory {
// reflection, by full qualified class name
public static Person getPersonWithFullQualifiedClassName(String personType) throws Exception {
Class<?> personClass = Class.forName(personType);
return getPersonWithClass(personClass);
}
// reflection, by passing class object
public static Person getPersonWithClass(Class personClass) throws Exception {
return (Person) personClass.newInstance();
}
// no reflection, the ordinary way
public static Person getPersonWithName(String personType) {
if (personType.equalsIgnoreCase("STUDENT")) {
return new Student();
} else if (personType.equalsIgnoreCase("TEACHER")) {
return new Teacher();
}
return null;
}
}
答案 0 :(得分:0)
由于您(很可能)没有在包的下面声明您的类,因此在类的第一行中使用了package xxx.yyy.zzz
,因此Java认为它是未命名(默认)包的一部分。已经说明了here
您可以通过将包设置为班级文件(最推荐)或更改完全合格的班级名称以删除无效的包(只需保留Student)来解决此问题。
答案 1 :(得分:0)
如果仅是通过反射来学习工厂模式,那么一个简单的解决方案是,使用您喜欢的文本编辑器将下面的代码复制到TestReflectionFactoryDesign.java
文件中,然后转到保存它的路径并运行javac TestReflectionFactoryDesign.java
,然后java TestReflectionFactoryDesign
查看结果。
public class TestReflectionFactoryDesign {
public static void main(String[] args) throws Exception {
Person student = PersonFactory.getPersonWithFullQualifiedClassName("Student");
student.say();
Person teacher = PersonFactory.getPersonWithClass(Teacher.class);
teacher.say();
Person student2 = PersonFactory.getPersonWithName("student");
student2.say();
}
}
class Student implements Person {
@Override
public void say() {
System.out.println("I am a student");
}
}
class Teacher implements Person {
@Override
public void say() {
System.out.println("I am a teacher");
}
}
interface Person {
void say();
}
class PersonFactory {
// reflection, by full qualified class name
public static Person getPersonWithFullQualifiedClassName(String personType) throws Exception {
Class<?> personClass = Class.forName(personType);
return getPersonWithClass(personClass);
}
// reflection, by passing class object
public static Person getPersonWithClass(Class personClass) throws Exception {
return (Person) personClass.newInstance();
}
// no reflection, the ordinary way
public static Person getPersonWithName(String personType) {
if (personType.equalsIgnoreCase("STUDENT")) {
return new Student();
} else if (personType.equalsIgnoreCase("TEACHER")) {
return new Teacher();
}
return null;
}
}
如果您在IDE中,并且不想更改代码,则应在代码的开始处放置package com.test.TestReflectionFactoryDesign
,这应该是创建Java文件的路径。