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Extract Interface

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description Extract Interface Overview

Extract Interface is a code refactoring tool integrated into JetBrains integrated development environments like IntelliJ IDEA. It allows software developers to generate a new interface by selecting specific public methods from an existing Java or Kotlin class. The refactoring process automatically updates the codebase to allow references to the original class through the newly created interface type. It is utilized by programmers to promote dependency on abstractions rather than concrete implementations.

help Extract Interface FAQ

What code does JetBrains Extract Interface generate?

The refactoring creates a new interface containing the selected public methods or members and updates the original class to implement it. The exact options depend on the language plugin and IDE, such as IntelliJ IDEA for Java or Rider for C#.

When is Extract Interface useful for unit testing?

It lets callers depend on a smaller abstraction instead of constructing the concrete class directly. A test can then provide a fake or mock implementation of that interface through tools such as Mockito in Java.

How is Extract Interface different from Extract Superclass?

An interface defines a contract without moving ordinary implementation state into a parent class. Extract Superclass creates an inheritance relationship and can move shared fields or implemented behavior, making it the heavier refactoring.

Will Extract Interface automatically rewrite every caller?

It can update selected type usages, but developers should review constructors, dependency-injection registrations, generics, and serialization code afterward. Compiling and running the test suite is important because a mechanically valid interface may still be too broad or expose the wrong members.