I'd like to suggest a new rule to detect reliance on the JVM default charset. This would need to cover multiple constructors/methods that have overloads with and without Charsets.

I'd be happy to contribute a pull request but would like some guidance on how it should be implemented. Should it be a single XPath rule that covers all of the APIs, or a separate rule for each?

APIs that I know of so far:

1. java.io.InputStreamReader#InputStreamReader(java.io.InputStream)
2. java.io.OutputStreamWriter#OutputStreamWriter(java.io.OutputStream)
3. java.io.PrintStream#PrintStream(java.io.File)
4. java.io.PrintStream#PrintStream(java.io.OutputStream)
5. java.io.PrintStream#PrintStream(java.io.OutputStream, boolean)
6. java.io.PrintWriter#PrintWriter(java.io.File)
7. java.io.PrintWriter#PrintWriter(java.io.OutputStream)
8. java.io.PrintWriter#PrintWriter(java.io.OutputStream, boolean)
9. java.io.PrintWriter#PrintWriter(java.lang.String)
10. java.lang.String#getBytes()
11. java.lang.String#String(byte[], int, int, int)
12. java.lang.String#String(byte[], int)
13. java.util.Formatter#Formatter(java.lang.String)
14. java.util.Formatter#Formatter(java.io.File)
15. java.util.Formatter#Formatter(java.io.OutputStream)
16. java.util.Scanner#Scanner(java.io.InputStream)
17. java.util.Scanner#Scanner(java.io.File)
18. java.util.Scanner#Scanner(java.nio.file.Path)
19. java.util.Scanner#Scanner(java.nio.channels.ReadableByteChannel)
20. java.util.Scanner#Scanner(java.io.InputStream)

Affects PMD Version:
6.20.0

Rule:
New Rule

Description:
Be sure to specify a character set for APIs that use the JVMs default character set to ensure stable decoding between different JVMs, programs, and servers.

Code Sample demonstrating the issue:

new InputStreamReader(inputStream);

should be written as, for example:

new InputStreamReader(inputStream, StandardCharset.UTF_8);