This post walks through how to use the == operator in Groovy and what to expect. Let’s start with an example.

This looks simple, and you can probably guess the output. Once executed, the actual output is:

Notice that == and equals() return different results — we expected true on lines 7 and 8 but got false. Why?

1. Is there a bug in Groovy?
2. Does == call equals()?

Plenty of questions can come to mind. The real reason:

The implementation of == in Groovy is slightly different from Java’s.

In Java, == means equality of primitive types or identity for objects.

In Groovy:

• If the operands are Comparable, == translates to a.compareTo(b) == 0.
• If they are not Comparable, == translates to a.equals(b).

To check for identity in Groovy, use the is() method, e.g. a.is(b).

Hope this helps.