HtmlSpecialCharsReplacer.java

import java.io.IOException;
import java.io.UncheckedIOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.StandardOpenOption;

class HtmlSpecialCharsReplacer {
	public static void main(final String... args) throws IOException {
		try (final var r = Files.lines(Path.of(args[0])); final var w = Files.newBufferedWriter(Path.of(args[0] + ".html"), StandardOpenOption.CREATE_NEW)) {
			r.forEachOrdered(line -> {
				try {
					for (final var c : line.trim().toCharArray()) {
						if (c < 128) {
							w.append(c);
						}
						else {
							w.append("&#" + (int) c + ";");
						}
					}
				}
				catch (final IOException e) {
					throw new UncheckedIOException(e);
				}
			});
		}
	}
}