The Java® Language Specification, Java SE 7 Edition, Fourth Edition

15.28. Constant Expressions

ConstantExpression:    Expression

A compile-time constant expression is an expression denoting a value of primitive type or a String that does not complete abruptly and is composed using only the following:

• Literals of primitive type and literals of type String (§3.10.1, §3.10.2, §3.10.3, §3.10.4, §3.10.5)

• Casts to primitive types and casts to type String (§15.16)

• The unary operators +, -, ~, and ! (but not ++ or --) (§15.15.3, §15.15.4, §15.15.5, §15.15.6)

• The multiplicative operators *, /, and % (§15.17)

• The additive operators + and - (§15.18)

• The shift operators <<, >>, and >>> (§15.19)

• The relational operators <, <=, >, and >= (but not instanceof) (§15.20)

• The equality operators == and != (§15.21 ...