What is the easiest way to compare Java POJO

Question

I have a class

public class A
{
    @Nonnull
    private final String m_a;

    @CheckForNull
    private final B m_b;

    @Nonnull
    private final List<C> m_c;

    @JsonCreator
    public A(
        @JsonProperty("a") @Nonnull final String a,
        @JsonProperty("b") @CheckForNull final B b,
        @JsonProperty("c") @Nonnull final List<C> c
    )
    {
        m_a = a;
        m_b = b;
        m_c = checkNotNull(c);
    }

    // getters ...
}

How would you recommend to compare if two A instances are equal?

I can use Jackson to serialize the JSON to a String (.writeValueAsString) and compare, but that is not cheap. Is it better if I override equals and hashcode and compare every field instead? What does it look like then?

override `equals()` and `hashCode()` is usually the solution which makes more sense — fantaghirocco, Dec 04 '20 at 16:19
Most IDE's can generate an `equals()` and `hashCode()` for you. — stdunbar, Dec 04 '20 at 16:22
Or, also not cheap, but definitely cheaper than converting to JSON: `if (other == null) return false; A that = (A)other; return Objects.equals(Arrays.asList(a, b, c), Arrays.asList(that.a, that.b, that.c));` (_please don't do this_) – and always override `hashCode` if you provide a custom `equals` implementation — knittl, Dec 04 '20 at 16:28
you'll have to make sure that `C` is also a comparable object when comparing the `c` lists — Bentaye, Dec 04 '20 at 17:59

score 1 · Accepted Answer · answered Dec 04 '20 at 22:35

1

Override equals() and hashCode() in class A and C, then you can compare two instances by A1.equals(A2)

And there are bunch of plugins that can generate them for you, example if you are using Intellij.

answered Dec 04 '20 at 22:35

lennon310

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What is the easiest way to compare Java POJO

1 Answers1