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Determining the Result Type of a Conditional Expression
Rule | Operand 2 | Operand 3 | Resultant Type |
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1 | Type T | Type T | Type T |
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10 | Other numeric | Other numeric | Promoted type of the second and third operands |
11 | T1 = boxing conversion(S1) | T2 = boxing conversion(S2) | Apply capture conversion to lub(T1,T2) |
The complexity of the rules that determine the result type of a conditional expression can lead to unintended type conversions. Consequently, the second and third operands of each conditional expression should have identical types. This recommendation also applies to boxed primitives.
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When the value of i in the second conditional expression falls outside the range that can be represented as a char, the explicit cast will truncate its value. This usage complies with exception NUM12-J-EX0 of NUM12-J. Ensure conversions of numeric types to narrower types do not result in lost or misinterpreted data.
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Automated detection of condition expressions whose second and third operands are of different types is straightforward.
Automated Detection
| Tool | Version | Checker | Description | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Parasoft Jtest |
| CERT.EXP55.COMT | Avoid using the conditional operator with mismatched numeric types |
Bibliography
Puzzle 8, "Dos Equis" | |
"Bx: Primitive Value Is Unboxed and Coerced for Ternary Operator" | |
[JLS 2013] | §15.25, "Conditional Operator ? :" |
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