java - How can I effectively use floats in equals()? -


i have following immutable hsl class use represent colour , aide in calculations on rgba colours little more finesse.

public class hsl {   protected final float hue;   protected final float saturation;   protected final float lightness;    public hsl(float hue, float saturation, float lightness) {     this.hue = hue;     this.saturation = saturation;     this.lightness = lightness;   }    // [snip] removed calculation helper functions    @override   public string tostring() {     return "hsl(" + hue + ", " + saturation + ", " + lightness + ")";   }    @override   public int hashcode() {     return         37 * float.floattointbits(hue) +         37 * float.floattointbits(saturation) +         37 * float.floattointbits(lightness);   }    @override   public boolean equals(object o) {     if (o == null || !(o instanceof hsl)) {       return false;     }      hsl hsl = (hsl)o;     // we're worried 4 decimal places of accuracy. that's more 24b rgb space can represent anyway.     return         math.abs(this.hue - hsl.hue) < 0.0001f &&         math.abs(this.lightness - hsl.lightness) < 0.0001f &&         math.abs(this.saturation - hsl.saturation) < 0.0001f;   } }

while don't foresee using particular class in hashmap or similar it's intermediary between similar rgba class uses ints it's internal storage, i'm concerned general case of using floats in equality. can make epsilon comparison small, , if make arbitrarily small there many float values can represented internally in multiple ways leading different values returned float.floattointbits. best way around this? or not issue in reality , i'm overthinking things?

the other answers great job of explaining why current design may cause problems. rather repeat that, i'll propose solution.

if care accuracy number of decimal places (it appears 4), multiply incoming float values 10,000 , manage them long values. equality , hashcode calculations exact.

i assume you've omitted getters class brevity. if so, ensure javadocs explain loss of precision occur when passing float class constructor , retrieving getter.


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