I generally prefer a very simple basic one without use of any libraries..
From Java 11 version
Since Java 11 there is a new method readString() to read small files as a String, preserving line terminators:
String content = Files.readString(path, StandardCharsets.US_ASCII);
Using getClass().getClassLoader(). getResourceAsStream(fileName)
private String slurpResources(String fileName) throws IOException {
var classLoader = getClass().getClassLoader();
return new String(classLoader.getResourceAsStream(fileName).readAllBytes());
}