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ConditionalExpression:
ConditionalOrExpression
ConditionalOrExpression ? Expression : ConditionalExpression EXP00-AJ. Use same type for second and third operands in conditional expressions

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Operand 2	Operand 3	Resultant type
type T	type T	type T
boolean	Boolean	boolean
Boolean	boolean	boolean
null	reference	reference
reference	null	reference
byte or Byte	short or Short	short
short or Short	byte or Byte	short
byte,short,char	const int*	byte,short,char if value of int representable
const int*	byte,short,char	byte,short,char if value of int representable
Byte	const int*	byte if int is representable as byte
const int*	Byte	byte if int is representable as byte
Short	const int*	short if int is representable as short
const int*	Short	short if int is representable as short
Character	const int*	char if int is representable as char
const int*	Character	char if int is representable as char
other	other	promoted type of the 2nd and 3rd operands
T1 = boxing conversion (S1)	T2 = boxing conversion(S2)	apply capture conversion to lub(T1,T2)

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Noncompliant Code Example

This non-compliant noncompliant example prints A65 instead of AA. The first print statement prints the value of alpha as type char, that is as A since the third operand is a constant expression of type int (0). The second statement, however, prints 65, the integer equivalent of A. This is because of numeric promotion between the second operand (int) and the third (char) resulting from the use of variable i.

Code Block

bgColor	#FFCCCC

public class expr {
  public static void main(String[] args) {
    char alpha = 'A';
    int i = 0;
    System.out.print(true  ? alpha  : 0);
    System.out.print(false ? i : alpha);
  }
}

Compliant Solution

This compliant solution recommends the use of same types for second and third operands. This helps avoid confusion due to clearer semantics.

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Code Block

bgColor	#ccccff

public class expr {
  public static void main(String[] args) {
    char alpha = 'A';
    int i = 0;
    System.out.print(true  ? alpha  : 0);
    System.out.print(false ? i : alpha);
  }
}

Risk Assessment

TODO

Rule	Severity	Likelihood	Remediation Cost	Priority	Level
EXP00-J	??	??	??	P??	L??

Automated Detection

TODO

Related Vulnerabilities

Search for vulnerabilities resulting from the violation of this rule on the CERT website.

References

JLS 15.25 Conditional Operator ? :
Java Puzzlers, Traps, Pitfalls, Corner Cases 2.8

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