Record it for easy review. . .

First, there are several types of getResourceAsStream in Java: 
1. Class.getResourceAsStream(String path) ： Path does not start with '/', the default is to take resources from the package where this class is located, starting with '/' is obtained from the ClassPath root. It just constructs an absolute path through the path, and finally gets resources from the ClassLoader.

2. Class.getClassLoader.getResourceAsStream(String path) ：By default, it is obtained from the ClassPath root. The path cannot start with '/', and finally the resource is obtained by the ClassLoader.

3. ServletContext. getResourceAsStream(String path)：By default, resources are taken from the root directory of the WebAPP. It doesn't matter if the path under Tomcat starts with '/'. Of course, this is related to the concrete container implementation.

4. The application built-in object under Jsp is an implementation of the above ServletContext.

Second, the usage of getResourceAsStream is roughly the following: 

the first: The file to be loaded and the .class file are in the same directory, for example: me.class under com.x.y and resource file myfile.xml

Then, there should be the following code:

 

me.class.getResourceAsStream("myfile.xml"); 

second:In the subdirectory of the me.class directory, for example: me.class under com.x.y, and the resource file myfile.xml in the com.x.y.file directory.

Then, there should be the following code:

 

me.class.getResourceAsStream("file/myfile.xml"); 

third:Not in the me.class directory, nor in the subdirectory, for example: me.class under com.x.y, and the resource file myfile.xml in the com.x.file directory.

Then, there should be the following code:
 

me.class.getResourceAsStream("/com/x/file/myfile.xml"); 

To sum up, it may be just two ways of writing

the first:In front of " / "

“ / ” represents the root directory of the project, for example, the project name is myproject, and “ / ” stands for myproject

me.class.getResourceAsStream("/com/x/file/myfile.xml"); 

second:No " / " in front

represents the directory of the current class

 

me.class.getResourceAsStream("myfile.xml"); 

me.class.getResourceAsStream("file/myfile.xml"); 

Finally, my own understanding: 
The file path read by getResourceAsStream is only limited to the project's source folder, including the project src root directory, and any location inside the class package, but if the configuration file path is in addition to the source This method is not used when you are in a folder other than a folder. (It can be simply recorded, this is just reading the files in the project. If the files in the C disk of Windows C cannot be read, there is something wrong to correct it...)

original:

A small example I wrote:https://github.com/ToBeAMonk/MyTest/blob/master/src/com/gty/test/GetResource.java