A DESCRIPTION OF THE REQUEST : Class sun.nio.cs.StandardCharsets is automatically generated from file standard-charsets, with lowercase preloaded hash maps via Hasher class. 1.) I propose to preload the hash maps with uppercase strings. 2.) I propose to save the classMap hash map. 3.) I propose, to set names (canonical + aliases) in file sun.io.cs.standard-charsets to uppercase letters, if even possible. Please note my comment on bug JDK-6795538 4.) Classes sun.nio.cs.AbstractCharsetProvider and sun.nio.cs.ext.ExtendedCharsets should be enhanced accordingly. I need this change for proceeding my work at https://java-nio-charset-enhanced.dev.java.net/. JUSTIFICATION : 1.) The majority of the canonical charset names are uppercase. So the lookup() method, derived from FastCharsetProvider, would profit in speed, because the transformation via a toUpper() method would not have so much work to do the transformation, than the actually given toLower() method. Additionally toUpper() would be potentially faster, as the 2nd term of { if (c >= 'a' && c <= 'z') } would only come to process in the rare case of character '_'. See proposed code in source section. 2.) If Map<String,Charset> cache would be retyped to Map<String,Object> and preloaded with the current values of Map<String,String> classMap, classMap could be saved, if lookup() method, derived from FastCharsetProvider, would be refactored according my proposal from bug JDK-6790402. This would speed-up method lookup() as explained there. 3.) This would additionally speed-up lookup from the hash maps in FastCharsetProvider, as the need of transformation by the toUpper() method would become very rare. For more details see: bug JDK-6790402 EXPECTED VERSUS ACTUAL BEHAVIOR : EXPECTED - General usage of uppercase names as keys for the hash maps, used in FastCharsetProvider. ACTUAL - Lowercase names as keys for the hash maps in FastCharsetProvider are generally used. ---------- BEGIN SOURCE ---------- static final String toUpper(final String s) { boolean allUpper = true; char[] ca = null; for (int i=0; i<s.length(); i++) { int c = s.charAt(i); if (c >= 'a' && c <= 'z') { if (allUpper) { ca = s.toCharArray(); allUpper = false; } ca[i] -= '\u0020'; } } return allUpper ? s : new String(ca); } ---------- END SOURCE ----------