internal int to double cast

[Bart Rider]

Hi there,

I just want to have a confirmation. I have two
variables like this:
int i = 10;
double d = 10.1;

Now I test whether d is greater and do such a thing:
if (i<d)
greater_double();
else
smaller_or_equal_double();

My question is the following. Does Java internally
converts the int(eger) i to double before comparison
(as I assume it does) or might there be circumstances
where it did not in such a case?

Best regards,
Bart

 

[Hendrik Maryns]

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Bart Rider schreef:

Hi there,

I just want to have a confirmation. I have two
variables like this:
int i = 10;
double d = 10.1;

Now I test whether d is greater and do such a thing:
if (i<d)
greater_double();
else
smaller_or_equal_double();

My question is the following. Does Java internally
converts the int(eger) i to double before comparison
(as I assume it does) or might there be circumstances
where it did not in such a case?

It does. See
http://java.sun.com/docs/books/jls/second_edition/html/conversions.doc.html#26917

HTH, H.

- --
Hendrik Maryns

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[liuyanbupt]

I find the following statements in "The Java™ Language Specification
Third Edition":
-----------------------------------------------------------------------------------------------------------------
5.6.2 Binary Numeric Promotion
....
· If either operand is of type double, the other is converted to
double.
....

15.20.1 Numerical Comparison Operators <, <=, >, and >=
The type of each of the operands of a numerical comparison operator
must be a
type that is convertible (§5.1.8) to a primitive numeric type, or a
compile-time
error occurs. Binary numeric promotion is performed on the operands
(§5.6.2). If
the promoted type of the operands is int or long, then signed integer
comparison
is performed; if this promoted type is float or double, then
floating-point comparison
is performed.

 

[Thomas Fritsch]

I just want to have a confirmation. I have two
variables like this:
int i = 10;
double d = 10.1;

Now I test whether d is greater and do such a thing:
if (i<d)
greater_double();
else
smaller_or_equal_double();

My question is the following. Does Java internally
converts the int(eger) i to double before comparison
(as I assume it does) or might there be circumstances
where it did not in such a case?

Just one addition to what the other posters correctly said:

You can check it by disassembling your java class with "javap -c ...".
There should be an "i2d" (int to double) instruction.

 

[Patricia Shanahan]

Hi there,

I just want to have a confirmation. I have two
variables like this:
int i = 10;
double d = 10.1;

Now I test whether d is greater and do such a thing:
if (i<d)
greater_double();
else
smaller_or_equal_double();

My question is the following. Does Java internally
converts the int(eger) i to double before comparison
(as I assume it does) or might there be circumstances
where it did not in such a case?

Best regards,
Bart

The JLS requires the same answer as if the program did the conversion of
i to double followed by the comparison.

An optimizing compiler might not actually generate the conversion, if it
noticed that i<d is a constant expression, did the comparison at compile
time, found that is is always true, and collapsed the if statement.

Patricia