Java 16 records BigDecimal equals & hashcode

Question

We use Lombok in our everyday project and I love it for the brevity it introduced. We have a tone of BigDecimal properties and with a little bit of effort made them ignore the scale in Lombok's generated equals and hashCode methods. Is there a way to do this in new record classes introduced in Java 16?

Answer 1

It sounds like you're after a general way to alter how equals and hashCode are implemented for fields that have a specific, existing type. There's no way to do this.

You have two options:

1. Implement equals and hashCode yourself on every record you define, like:

record Test(BigDecimal v) {
    public int hashCode() {
        return Util.hashCodeWithoutScale(v);
    }

    public boolean equals(Object o) {
        return Util.equalsForBigDecimalWithoutScale(this, o);
    }
}

2. Consistently use a wrapper that you define:

record Test(BigDecimalWrapperThatIgnoresScaleInHashCodeAndEquals x) {
}

For us this feature seems unusable.

While BigDecimal is close to your requirements, the mismatch in behaviour suggests you may have better luck with use of a wrapper, or an alternate class instead, even if it largely delegates to the existing class.