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cast a number from Double to int [SOLVED]

 
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Hi all. I know that normally i can`t cast from a higher type as double to a lower type as int, but i just expect that if i am sure 100% my double number fit in an integer to be able to cast it, and the decimal numbers truncated. But when i try to cast from Double to int didn`t work becouse

Examples:


Chapter 3, Pag 94
I just try to calculate the value of an integer value greater than max short range, put in a short by casting Context Code:

The book "short ticketTake = (short) 1921222  //stored as 20678 "

My code:



calcNr it`s  a Double obj, becouse i need the floor method.
So basically if i try to cast (int)(calcNr) // doesn`t work becouse Double to int can`t cast, but if i just type (int)(calcNr+0) then i think the Double obj will pass the double value and then become castable for int i just suppose it happen this, and the corect version that i found after some times that i tryed the code (int)(calcNr.doubleValue()) in this case the obj will return a double value, castable to int by trouncating the decimal part.
I am not sure why (int)(calcNr+0) works fine.

 
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Alex Damian wrote:Hi all. I know that normally i can`t cast from a higher type as double to a lower type as int


You can, you just have to perform an explicit cast.

but i just expect that if i am sure 100% my double number fit in an integer to be able to cast it


This has nothing to do with it. You may always explicitly cast one primitive numeric type to another primitive numeric type.

But when i try to cast from Double to int didn`t work


Because Double isn't a primitive, but an object.

I am not sure why (int)(calcNr+0) works fine.


Because the + operator returns int, long, double or String, depending on the types of the operands. calcNr + 0 returns a double, and double can be cast to int. calcNr by itself is a Double, and you may not cast Double to int.
 
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Stephan van Hulst wrote:Because Double isn't a primitive, but an object.



Boldfaced for emphasis. A Double cannot be cast to a primitive, but the Double intValue() method can do what you want.

For that matter, you can do a Double x; int i = (int)x.doubleValue(); or even (int)x.floatValue(), but that's just making things more complicated.
 
Alex Damian
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Stephan van Hulst wrote:

Alex Damian wrote:Hi all. I know that normally i can`t cast from a higher type as double to a lower type as int


You can, you just have to perform an explicit cast.

but i just expect that if i am sure 100% my double number fit in an integer to be able to cast it


This has nothing to do with it. You may always explicitly cast one primitive numeric type to another primitive numeric type.

But when i try to cast from Double to int didn`t work


Because Double isn't a primitive, but an object.

I am not sure why (int)(calcNr+0) works fine.


Because the + operator returns int, long, double or String, depending on the types of the operands. calcNr + 0 returns a double, and double can be cast to int. calcNr by itself is a Double, and you may not cast Double to int.



Thank you !!
 
Alex Damian
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Tim Holloway wrote:

Stephan van Hulst wrote:Because Double isn't a primitive, but an object.



Boldfaced for emphasis. A Double cannot be cast to a primitive, but the Double intValue() method can do what you want.

For that matter, you can do a Double x; int i = (int)x.doubleValue(); or even (int)x.floatValue(), but that's just making things more complicated.



Thank you for the help !!
 
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