The following character sequences, formed from ASCII letters, are reserved for use as keywords and cannot be used as identifiers (§3.8):
Keyword: one of abstract continue for new switch assert default if package synchronized boolean do goto private this break double implements protected throw byte else import public throws case enum instanceof return transient catch extends int short try char final interface static void class finally long strictfp volatile const float native super while
The keywords const and goto are reserved, even though they are not currently used. This may allow a Java compiler to produce better error messages if these C++ keywords incorrectly appear in programs.
While true and false might appear to be keywords, they are technically Boolean literals (§3.10.3). Similarly, while null might appear to be a keyword, it is technically the null literal (§3.10.7).