4.16 Constant Expressions

A constant expression is an expression that always produces the same result. More precisely, a constant expression is an expression that produces a pure value of a primitive data type and is only composed of the following:

• Literals of primitive data types

• String literals

• Variables that are declared final and are initialized by constant expressions

• Type casts to primitive data types or the type String

• The unary operators + -, ~, and !

• The binary operators *, /, %, +, -, <<, >>, >>>, <, <=, >=, >, ==, !=, &, ^, |, &&, and ||

• The ternary operator ?:

Note that expressions that use ++, - -, and instanceof are not constant expressions. Also note that expressions that produce or contain references to objects that are not String objects are never constant expressions.

The compiler generally evaluates a constant expression and substitutes the result for the expression during the compilation process.

References Additive Operators; Bitwise/Logical Operators; Boolean Operators; Casts; Conditional Operator; Equality Comparison Operators; Interface Variables; Local Variables; Literals; Multiplicative Operators; Relational Comparison Operators; Shift Operators; Unary Operators; Variables