Tip #62: Limitations of Java Records

While Java Records are a powerful tool for modeling immutable data, they come with certain limitations that are essential to understand:

1. No Inheritance
   A record automatically extends java.lang.Record and is implicitly final. Thus, it cannot inherit from other classes or be a superclass. If your design relies on inheritance, records are not a fit.

2. No Additional Fields or Initializers
   You cannot declare instance fields or instance initializers in a record. The state of a record is entirely determined by its components (parameters in its header).

3. Cannot Be Abstract or Contain Native Methods
   Records are concrete classes designed for value-carrier roles. Declaring a record as abstract or adding native methods is not allowed.

4. Library Incompatibility
   Libraries that require mutating an object’s state or rely on reflective field access may face issues with records due to their immutable nature. For instance, some versions of Jackson might require specific configurations to handle records properly.

// Invalid in records
private int extraField; // Error
{
    System.out.println("Instance initializer"); // Error
}

When Should You Avoid Records?

If your class needs:

• Complex hierarchies or polymorphic behavior,

• Instance-specific fields beyond the record header,

• Libraries or frameworks that depend on mutable or modifiable state,

then a traditional class might be more appropriate.

Records shine when immutability, brevity, and clarity are priorities. Also, with pattern matching, we will see how records are a great addition to the Java language.

Happy coding!