Software Development

Java Lambda Expression Parameter and Return Types

This post shows how to pass the type of parameters to and return from a Lambda expression in Java based on the functional interface abstract method definition.  The types must be sub-types or exact match to those defined in the abstract method for the parameters and return type.

Using the Function Interface And Lambda Expression

Consider the following method.

It accepts a Person object and a Function functional interface that accepts and returns a Person object.

Person class and its sub-class

The Student class extends the Person class.

Now Polymorphism allows us to pass or/and return Student objects instead of Person objects.

The codes output

But…

When we assign a Lambda expression to a variable, we need to declare that variable using Generics.

This results in a compilation error.

Because

The Full Codes

 

Got comments or suggestions? We disabled the comments on this site to fight off spammers, but you can still contact us via our Facebook page!.


You Might Also Like