使用“class.getResource（”/“）”时出现NullPointerException(NullPointerException when using “class.getResource(”/“)”)

 我正在编写一个包装在两个Jar文件中的应用程序：startup.jar和resource.jar。 在resource.jar中我有一个java文件（ResourceFile.java）具有以下代码： 
 
String dir = ResourceFile.class.getResource("/").getPath();
 
 应用程序应该通过运行“startup.jar”（两个jar文件放在同一个目录中）来启动，但我总是在上面的代码中得到NullPointerException，我也试图将它改为下面的代码： 
 
String dir = ResourceFile.class.getClassLoader().getResource("").getPath();
 
 得到了同样的错误。 
 
System.out.println(ResourceFile.class.getResource("/") == null);
 
 打印真实。 
 
 我环顾四周，找不到可以帮助我解决问题的解决方案。 

I'm writing an application which is packaged in two Jar files: startup.jar and resource.jar. In resource.jar I have a java file(ResourceFile.java) has below code:
 
String dir = ResourceFile.class.getResource("/").getPath();
 
The application should be started up by running the "startup.jar"(two jar files are put in the same directory), but I always get NullPointerException at above code, I have also tried to change it to below code:
 
String dir = ResourceFile.class.getClassLoader().getResource("").getPath();
 
Got the same error.
 
System.out.println(ResourceFile.class.getResource("/") == null);
 
print true.
 
I have looked around for a bit and I couldn't find a solution that could help me solve the problem.

原文：https://stackoverflow.com/questions/41789127