About Apache Commons EqualsBuilder and HashCodeBuilder and null values

Question

The classes EqualsBuilder and HashCodeBuilder from the Apache Commons Lang library can be used for object comparison purposes.

E.g., one can test equality between two Person objects like follows:

Person p1 =...;
Person p2 =...;
boolean equals = new EqualsBuilder().
        append(p1.name, p2.name).
        append(p1.secondname, p2.secondname).
        append(p1.surname, p2.surname).
        append(p1.age, p2.age).
        isEquals();

Suppose that a field is not mandatory, e.g. secondname. How does EqualsBuilder and HasCodeBuilder handle this fact? Is the comparison done on this field or not? Or the comparison on a null field can be skipped as a special option?

Isn't this pretty easy to test for yourself? (It would be nice if it were documented, admittedly - perhaps you could send in a patch once you've checked the behaviour.) — Jon Skeet, May 05 '13 at 08:00
It's also easy to look at the source code to figure it out. It's free, open-source software — JB Nizet, May 05 '13 at 08:04

score 4 · Answer 1 · answered May 05 '13 at 08:03

These two methods will consider p1.name and p2.name to be equal if they're both null. Here's the relevant part of the freely available source code:

public EqualsBuilder append(Object lhs, Object rhs) {
    if (isEquals == false) {
        return this;
    }
    if (lhs == rhs) {
        return this;
    }
    ...

About Apache Commons EqualsBuilder and HashCodeBuilder and null values

1 Answers1