Why is .* used in Java? For example
double probability = 1.*count/numdata;
gives the same output as:
double probability = count/numdata;
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user4345738
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What type are `cout` and `numdata`? – Codor Dec 10 '14 at 12:50
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Not if `count` and `numdata` are integers. – Alexis C. Dec 10 '14 at 12:50
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they are both integers, what difference does it make? – user4345738 Dec 10 '14 at 12:50
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Read about integer division. – Alexis C. Dec 10 '14 at 12:53
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Possible Duplicate: [Division of integers in Java](http://stackoverflow.com/questions/7220681/division-of-integers-in-java) – Dev Dec 10 '14 at 12:57
1 Answers
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If count and numdata are integral: int or long the result again will be integral (integer division), so the fractions gets lost; truncated, not even rounded. As a probability is between 0.0 and 1.0, and so numdata >= count, you'll get only 0 or 1.
Simplest would be to make the division floating point:
double probability = ((double)count) / numdata;
or (more obfuscating though!)
double probability = count;
probability /= numdata;
Joop Eggen
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so int can store for example 26.5? isn't int always whole numbers for example 26? – user4345738 Dec 10 '14 at 12:58
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53 / 2 = 26, (int) 26.5 == 26. "integer" or the French "entier" means whole number, and you are right: only whole numbers can be stored. – Joop Eggen Dec 10 '14 at 13:00