UTF-8 / ISO-8859-1 spelunking

Main.java

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.charset.CharacterCodingException;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;
import java.nio.charset.CodingErrorAction;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;

public class Main {

    public static void main(String[] args) throws IOException {
        System.out.println("Starting");
        Files.find(Paths.get(""), Integer.MAX_VALUE,
                        (path, basicFileAttributes) -> !path.toString().contains("/target/") && path.toString().endsWith(".properties"))
                .forEach(Main::process);
    }

    private static void process(Path path) {
        String fileName = path.toString();
        byte[] contents;
        try {
            contents = Files.readAllBytes(path);
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
        if (!isEncoded(contents, StandardCharsets.US_ASCII)) {
            boolean isUtf8 = isEncoded(contents, StandardCharsets.UTF_8);
            boolean isIso88591 = isEncoded(contents, StandardCharsets.ISO_8859_1);
            if (isUtf8 && isIso88591) {
                System.err.println("Case 1: " + fileName + " is valid UTF-8 and valid ISO-8859-1");
            } else if (isUtf8) {
                System.err.println("Case 2: " + fileName + " is valid UTF-8 but not valid ISO-8859-1");
            } else if (isIso88591) {
                System.err.println("Case 3: " + fileName + " is not valid UTF-8 but is valid ISO-8859-1");
            } else {
                System.err.println("Case 4: " + fileName + " is neither valid ASCII nor valid UTF-8 nor valid ISO-8859-1");
            }
        }
    }


    private static boolean isEncoded(byte[] bytes, Charset charset) {
        CharsetDecoder decoder = charset.newDecoder();
        decoder.onMalformedInput(CodingErrorAction.REPORT);
        decoder.onUnmappableCharacter(CodingErrorAction.REPORT);
        ByteBuffer buffer = ByteBuffer.wrap(bytes);

        try {
            decoder.decode(buffer);
            return true;
        } catch (CharacterCodingException e) {
            if (charset.equals(StandardCharsets.US_ASCII)) {
                Object foo = "bar";
            }
            return false;
        }
    }
}