This chapter covers more of the language basics. The information here follows a progression: first, the basics of names and identifiers, then how names are connected in expressions by operators, followed by the rules to evaluate expressions.
The last part of the chapter describes practical limits on accuracy, casting and conversions. If you are new to floating point arithmetic, some of this may come as a bit of a shock. The chapter finishes up by presenting the standard class java.lang.Math.
Keywords are reserved words, which means they cannot be used as identifiers. Java now has 50 keywords (“enum” became a keyword in JDK 1.5). These are the keywords.
abstract continue for new switch
assert default goto package synchronized
boolean do if 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 words, even though they are not used anywhere in Java. This allows future expansion, or (unlikely but claimed) better diagnostic messages if a programmer uses them in a way they might be used in C++.
The words “true” and “false” look like keywords, but technically they are boolean literals. Similarly,”null” looks like it should be in the keyword list, but it is technically the null literal for reference types. The classification of these three words as literals, not keywords, doesn't have any subtle side effects, and it keeps the type system a bit cleaner.