Kotlin annotations for Java callers (@JvmStatic, @JvmField) - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the @JvmStatic annotation do in Kotlin?

It makes a Kotlin function or property appear as a static method or field in Java, allowing Java code to call it without needing an instance.

beginner

How does @JvmField affect Kotlin properties when accessed from Java?

It exposes the Kotlin property as a public Java field, removing the getter/setter methods and allowing direct field access from Java.

intermediate

When should you use @JvmStatic in Kotlin companion objects?

Use <code>@JvmStatic</code> on functions or properties inside companion objects to let Java callers access them as static members of the containing class.

intermediate

What is the difference between a Kotlin property with @JvmField and a regular Kotlin property without it when accessed from Java?

With @JvmField, Java code accesses the property as a field directly. Without it, Java accesses it via getter/setter methods.

advanced

Can @JvmStatic be used on top-level Kotlin functions?

No, @JvmStatic is only applicable inside companion objects or named objects. Top-level functions are already static in Java bytecode.

What does @JvmStatic do when applied to a function inside a Kotlin companion object?

A Removes the function from the bytecode

B Makes the function callable as a static method from Java

C Converts the function to an extension function

D Makes the function private

@JvmStatic allows Java code to call the function as a static method on the containing class.

Which annotation exposes a Kotlin property as a public field in Java, skipping getter/setter methods?

A @JvmField

B @JvmStatic

C @JvmOverloads

D @JvmName

@JvmField exposes the property as a public field in Java.

Can @JvmStatic be used on top-level Kotlin functions to make them static in Java?

A No, it only works inside companion objects or named objects

B Yes, always

C Yes, but only for private functions

D No, it only works on properties

Top-level functions are already static in Java bytecode, so @JvmStatic is not needed and only works inside companion or named objects.

What happens if you do NOT use @JvmField on a Kotlin property accessed from Java?

A Java accesses it as a static field

B The property is private in Java

C Java cannot access the property

D Java accesses it via getter/setter methods

Without @JvmField, Java uses getter/setter methods to access Kotlin properties.

Which Kotlin annotation helps Java callers access companion object members as static members of the class?

A @JvmField

B @JvmSuppressWildcards

C @JvmStatic

D @JvmSynthetic

@JvmStatic makes companion object members appear as static members in Java.

Explain how @JvmStatic and @JvmField improve Kotlin and Java interoperability.

Think about how Java expects static methods and fields.

Describe when and why you would use @JvmStatic inside a Kotlin companion object.

Consider Java's static method calling style.