Can Lambda Expressions Be Compared in Java?

Comparing Lambda Expressions

Q: Is there a way to compare lambda expressions?

A: The Java language specification does not define a way to compare lambda expressions, but it allows implementations to provide their own comparison methods.

Implementation Considerations

Currently, there is a 1:1 relationship between the synthetic classes that implement lambdas and the capture sites in the program. Therefore, two lambda expressions that capture the same variable at the same capture site will be represented by the same instance and can be compared using reference equality. However, if two lambda expressions capture the same variable at different capture sites or are non-capturing, they may be represented by different instances and cannot be compared using reference equality.

Alternatives

If you need to compare lambda expressions, one alternative is to use serialization. Serializable lambdas can be compared using their serialized form. Another alternative is to use method references instead of lambda expressions. Method references can be compared using reference equality if they refer to the same method.

Human-Readable Output

It is not currently possible to obtain a human-readable string representation of a lambda expression. However, it is possible to extract the name of the method that the lambda expression refers to using reflection.

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