I have question to everybody.
int a = (int) ((0.7 + 0.1) * 10)
After executing of this code, a = 7. I can`t understand why, because (0.7+0.1)=0.8 and 0.8*10=8. Can anybody tell me why? Thanks!
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7Try printing the result of `0.7 + 0.1`, and you'll have your answer. – FThompson Jun 29 '13 at 19:31
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The result is 0. All the same I don`t understand why a = 7 – Artyom Gilevich Jun 29 '13 at 19:36
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@user2535193 How are you printing that? Post the code that's responsible of printing. – Maroun Jun 29 '13 at 19:37
3 Answers
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The issue is that neither 0.1 nor 0.7 can be represented exactly as double:
0.1gets represented as approximately0.10000000000000000555.0.7gets represented as approximately0.69999999999999995559.
Their sum is approximately 0.79999999999999993339. Multiplied by ten and truncated, this gives 7.
What Every Computer Scientist Should Know About Floating-Point Arithmetic is an excellent read on the subject.
NPE
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It's float arithmetic, it gets floored.
What's happening here is that (0.1+0.7) is really close to 0.8 but it's not actually 0.8, when you multiply it by 10 you get 7.9999... , when you floor that, you get 7.
Benjamin Gruenbaum
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The decimal portion of ints in Java is truncated. You can either make x and y floating point variables or just cast them to float and cast them back to get an int as the final result.
0x6C38
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