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

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Noncompliant Code Example

This 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.

public class exprExpr {
  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 the same types for the second and third operands . This of the conditional expressions. The clearer semantics helps avoid confusion due to clearer semantics.

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

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

Risk Assessment

TODOIf the types of the second and third operands in a conditional expression are not the same then the result of the conditional expression may be unexpected.

Automated Detection

TODO

Related Vulnerabilities

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

References

\[[JLS 05|AA. Java References#JLS 05]\] Section 15.25 Conditional Operator ?

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\[[Bloch 05|AA. Java References#Bloch 05]\] Puzzle 8: Dos Equis