How to read files in different directories

//The file directory is in the same directory as JsonToJava.class

Reader reader = new InputStreamReader(JsonToJava.class.getResourceAsStream("js/Server2.json"), "UTF-8");

//The file directory and JsonToJava.class are in different levels. The file directory level of JsonToJava.class is deeper than the directory where /js/Server2.json is located.

Reader reader = new InputStreamReader(JsonToJava.class.getResourceAsStream("../js/Server2.json"), "UTF-8");

//Do not consider the directory hierarchy of resource directories and classes

InputStream in = new FileInputStream(System.getProperty("user.dir")+"/cfg/js/Server1.json");

Reader reader = new InputStreamReader(in, "UTF-8");