从包含环境变量的路径中检查Java是否存在文件

Question

Is there an existing Java solution to resolve file paths containing environment variables?

I need to convert this (simplified) method to handle the case where the provided path contains an environment variable (like %PROGRAMFILES(X86)%\\SomeProgram\\SomeFile.ini).

I know how to write code to extract the variable names, fetch their values and substitute them in the provided string but I can't help but feel I'm reinventing the wheel...

boolean isValidPath(String pathToValidate) {
  File f = new File(pathToValidate);
  if(f.exists()) {
    return true;
  }  
  return false;
}

Answer 1

Almost sure it does not exist in standard library simply because any environment variable is very specific in its usage. Some allow lists delimited by semicolons like PATH, some - only one single value. Also relying on values of env vars means that code becomes more platform-specific, and jre seems to avoid it at any reasonable cost.

There are already a couple of implementations of such substitutors on github, for example https://github.com/Haufe-Lexware/java-env-replacer .

Answer 2

You can actually get the environment variables details by calling System.getenv() and then you can write some logic (sample shown below) to achieve what you wanted:

public boolean isValidPath(String pathToValidate) {
  String envValue = "";
  for (String envName : env.keySet()) {
      if(pathToValidate.contains(envName)) {
             envValue= env.get(envName);
             break;
      }
  }
  //replace the envValue in pathToValidate
  //Then check file exists or not & return true/false
}