CODEWITHSUNDEEP
javafloating-accuracy
James P.
James P.

Reputation: 19607

Increment/decrement to floating number seem off

I have a float to represent the zoom factor on an image.

setZoomPercent( currentZoomPercent - 0.1f );

The trouble I'm having is that the decrementation is giving the following result. How can I avoid this ?

Zoom:100.0
Zoom:99.9
Zoom:99.8
Zoom:99.700005
Zoom:99.600006
Zoom:99.50001
Zoom:99.40001
Zoom:99.30001
Zoom:99.20001
Zoom:99.10001
Zoom:99.000015
Zoom:98.90002
Zoom:98.80002

P.S: I'm guessing it has to do with the binary representation of 0.1 in binary.

Upvotes: 0

Views: 490

Answers (1)

Evgeniy Dorofeev
Evgeniy Dorofeev

Reputation: 136002

You can avoid it by using BigDecimal

    BigDecimal d1 = new BigDecimal("100.00");
    BigDecimal d2 = new BigDecimal("0.1");
    for(int i = 0; i < 100; i++) {
        d1 = d1.subtract(d2);
        System.out.println(d1);
    }

produces

99.90
99.80
99.70
99.60
99.50
99.40
99.30
99.20
...

Upvotes: 4

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