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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


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