[LANG-1062] Use Java 8 features to improve EqualsBuilder

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 3.3.2
• Fix Version/s: 4.0
• Component/s: lang.builder.*
• Assignee: Unassigned
• Reporter: Bruce Brouwer
• Created: 10/Nov/14 18:14
• Updated: 13/Nov/16 17:58

Description

Remove the need for boilerplate code still necessary with EqualsBuilder. Instead of checking for instanceOf or equality checks, it would be nice to be able to write this:

public boolean equals(final Object obj) {
  return EqualsBuilder.test(this, obj).append(this.id, o -> o.id).isEquals();
}

I think this could generally work with a subclass of EqualsBuilder with a generic type, like this:

public class LambdaEqualsBuilder<T> extends EqualsBuilder {
    private final T obj;

    public LambdaEqualsBuilder(final T _this, final Object obj) {
        if (_this != obj && !_this.getClass().isInstance(obj)) {
            appendSuper(false);
            this.obj = null;
        } else {
            this.obj = (T) obj;
        }
    }

    public <P> LambdaEqualsBuilder<T> append(final P a, final Function<T, P> b) {
        if (isEquals()) {
            return (LambdaEqualsBuilder<T>) append(a, b.apply(obj));
        }
        return this;
    }

    // This might actually go in EqualsBuilder itself
    public static <E> LambdaEqualsBuilder<E> test(final E _this, final Object _that) {
        return new LambdaEqualsBuilder<E>(_this, _that);
    }
}

Issue Links

• is related to: LANG-923 JDK 1.8 Changes