About Question enthuware.ocajp.i.v7.2.1059 :
Posted: Wed Jan 23, 2013 1:15 am
I didn't know the return value of Math.random() can be represented like .05. Where is the specification?
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I wondered til now what the bounds were for the update clause.The third part (i.e. the update part) of the for loop does not allow every kind of statement. It allows only the following statements here: Assignment, PreIncrementExpression, PreDecrementExpression, PostIncrementExpression, PostDecrementExpression, MethodInvocation, and ClassInstanceCreationExpression.
Where is this specified?The third part (i.e. the update part) of the for loop does not allow every kind of statement. It allows only the following statements here: Assignment, PreIncrementExpression, PreDecrementExpression, PostIncrementExpression, PostDecrementExpression, MethodInvocation, and ClassInstanceCreationExpression.
14.8 defines StatementExpression:ForUpdate:
StatementExpressionList
StatementExpressionList:
StatementExpression
StatementExpressionList , StatementExpression
HTH,ExpressionStatement:
StatementExpression ;
StatementExpression:
Assignment
PreIncrementExpression
PreDecrementExpression
PostIncrementExpression
PostDecrementExpression
MethodInvocation
ClassInstanceCreationExpression
So basically, the type of the value returned by both the operands is actually converted to a common type by using one of the above rules. In your example, the second last line of the above quote applies.The type of a conditional expression is determined as follows:
If the second and third operands have the same type (which may be the null type), then that is the type of the conditional expression.
If one of the second and third operands is of primitive type T, and the type of the other is the result of applying boxing conversion (§5.1.7) to T, then the type of the conditional expression is T.
If one of the second and third operands is of the null type and the type of the other is a reference type, then the type of the conditional expression is that reference type.
Otherwise, if the second and third operands have types that are convertible (§5.1.8) to numeric types, then there are several cases:
If one of the operands is of type byte or Byte and the other is of type short or Short, then the type of the conditional expression is short.
If one of the operands is of type T where T is byte, short, or char, and the other operand is a constant expression (§15.28) of type int whose value is representable in type T, then the type of the conditional expression is T.
If one of the operands is of type T, where T is Byte, Short, or Character, and the other operand is a constant expression (§15.28) of type int whose value is representable in the type U which is the result of applying unboxing conversion to T, then the type of the conditional expression is U.
Otherwise, binary numeric promotion (§5.6.2) is applied to the operand types, and the type of the conditional expression is the promoted type of the second and third operands.
Note that binary numeric promotion performs value set conversion (§5.1.13) and may perform unboxing conversion (§5.1.8).
Otherwise, the second and third operands are of types S1 and S2 respectively. Let T1 be the type that results from applying boxing conversion to S1, and let T2 be the type that results from applying boxing conversion to S2.
The type of the conditional expression is the result of applying capture conversion (§5.1.10) to lub(T1, T2) (§15.12.2.7).