The FileInputStream and FileOutputStream classes contains a finalizer method which will cause garbage collection pauses.

The FileReader and FileWriter constructors instantiate FileInputStream and FileOutputStream, again causing garbage collection issues while finalizer methods are called.

• Use Files.newInputStream(Paths.get(fileName)) instead of new FileInputStream(fileName).
• Use Files.newOutputStream(Paths.get(fileName)) instead of new FileOutputStream(fileName).
• Use Files.newBufferedReader(Paths.get(fileName)) instead of new FileReader(fileName).
• Use Files.newBufferedWriter(Paths.get(fileName)) instead of new FileWriter(fileName).

Links:

• https://pmd.github.io/latest/pmd_rules_java_performance.html#avoidfilestream