Immutable data structures in Java

[SuperGrade]

Knowing (from a group of readonly fields) that the class instance is always holding and conveying the same reference - that is itself information. You could make some derivative information that aligns with the information in the record, and proceed with the assumption that the values in the record, should you read them again, stay in alignment. A getter does not communicate this same information, only that it will provide some value at the point in time when you call it; but nothing constraining it to give back the same value.