15.27 Constant Expression

ConstantExpression:

	Expression

A compile-time constant expression is an expression denoting a value of primitive type or a String that is composed using only the following:

• Literals of primitive type and literals of type String
• Casts to primitive types and casts to type String
• The unary operators +, -, ~, and ! (but not ++ or --)
• The multiplicative operators *, /, and %
• The additive operators + and -
• The shift operators <<, >>, and >>>
• The relational operators <, <=, >, and >= (but not instanceof)
• The equality operators == and !=
• The bitwise and logical operators &, ^, and |
• The conditional-and operator && and the conditional-or operator ||
• The ternary conditional operator ? :
• Simple names that refer to final variables whose initializers are constant expressions
• Qualified names of the form TypeName . Identifier that refer to final variables whose initializers are constant expressions

Compile-time constant expressions are used in case labels in switch statements (§14.9) and have a special significance for assignment conversion (§5.2).

Examples of constant expressions:

true
(short)(1*2*3*4*5*6)
Integer.MAX_VALUE / 2
2.0 * Math.PI
"The integer " + Long.MAX_VALUE + " is mighty big."

. . . when faces of the throng turned toward him and ambiguous eyes stared
into his, he assumed the most romantic of expressions . . .
--F. Scott Fitzgerald, This Side of Paradise (1920)