public static SortedMap<String, Charset> requiredCharsets() {
		// maybe cache?
		final TreeMap<String, Charset> m = new TreeMap<>(String.CASE_INSENSITIVE_ORDER);
		m.put(StandardCharsets.ISO_8859_1.name(), StandardCharsets.ISO_8859_1);
		m.put(StandardCharsets.US_ASCII.name(), StandardCharsets.US_ASCII);
		m.put(StandardCharsets.UTF_16.name(), StandardCharsets.UTF_16);
		m.put(StandardCharsets.UTF_16BE.name(), StandardCharsets.UTF_16BE);
		m.put(StandardCharsets.UTF_16LE.name(), StandardCharsets.UTF_16LE);
		m.put(StandardCharsets.UTF_8.name(), StandardCharsets.UTF_8);
		return Collections.unmodifiableSortedMap(m);
	}
Constructs a sorted map from canonical charset names to charset objects required of
every implementation of the Java platform.
<p>
From the Java documentation
<a href="https://docs.oracle.com/javase/7/docs/api/java/nio/charset/Charset.html">
Standard charsets</a>:
</p>

@return An immutable, case-insensitive map from canonical charset names to charset
objects.
@see Charset#availableCharsets()
spring-cloud-alibaba-starters/spring-cloud-alibaba-commons/src/main/java/com/alibaba/cloud/commons/io/Charsets.java