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declaration of variable problem

Posted on 2008-10-06
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Last Modified: 2010-03-30
I want to do something like this:

if (some condition) {
  int x;
}
else {
  double x;
}

x = something;

I want x to be either int or double, depending on some condition
How can this be done?
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Question by:allelopath
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4 Comments
 
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Accepted Solution

by:
Kevin Cross earned 500 total points
ID: 22655009
Technically you can do something like this:
http://java.sun.com/j2se/1.3/docs/api/java/lang/Number.html

You can then use .doubleValue() or .intValue().
boolean isInt = true;
Number x;
 
if (isInt) {
    x = new Integer(0);
} else {
    x = new Double(0);
}
 
x = 1.0;

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Expert Comment

by:sciuriware
ID: 22656775
In effect, what you want is impossible in many languages.
Only in C (and derived languages) there is a thing called a 'union':

union
{
    int i;
    double d;
} x;

Then you can say: x.i = 6;   or x.d = 7.8
But even then you can not use the integer entered as a double.

Can you tell us what you really want.
I can not believe you want to save a few bytes of space .................

;JOOP!
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LVL 59

Assisted Solution

by:Kevin Cross
Kevin Cross earned 500 total points
ID: 22658060
Here, I will do the impossible again!  

@sciuriware, just messing with you...

@allelopath, you cannot have the variable instantiated only under the if statement to use later as variables under the ifs in your code above are scoped only to the if statement containing them.  To fix that problem you must move the declaration of x above the if.  Once you do that you have the problem of only being able to declare one type.  Either declare a type using UNION which quite honestly is no different than creating a class called IntDouble that has members i and d and do the same thing in languages without union.  Alternative, is use a base class of types you want like in this case we can use Number which is base class for Integer and Double.  Those are not the primitive types you are using, but as you can see you can get the primitives easily using .intValue() or .doubleValue().

Hope that helps.
boolean isInt = true;
Number x = 1.78;
 
JOptionPane.showMessageDialog(null, (isInt)?x.intValue():x.doubleValue());

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Expert Comment

by:sciuriware
ID: 22658325
Correct!

;JOOP!
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