Calling Java from Kotlin seamlessly - Cheat Sheet & Quick Revision

Recall & Review

beginner

How do you call a Java method from Kotlin?

You call a Java method from Kotlin just like calling a Kotlin method, using the Java class name and method name directly.

intermediate

What happens to Java's nullability when accessed from Kotlin?

Kotlin treats Java types as platform types, meaning Kotlin does not enforce null-safety on them, so you must handle nulls carefully.

beginner

Can Kotlin access Java static methods directly? How?

Yes, Kotlin accesses Java static methods using the class name, just like in Java, for example: JavaClass.staticMethod().

intermediate

How does Kotlin handle Java getters and setters?

Kotlin treats Java getters and setters as properties, so you can access them like Kotlin properties without calling get/set explicitly.

intermediate

What annotation helps Kotlin understand Java nullability better?

Annotations like @Nullable and @NotNull in Java help Kotlin understand nullability and improve safety when calling Java code.

How do you call a Java static method named 'print' from Kotlin?

A print()

B JavaClass->print()

C print.JavaClass()

D JavaClass.print()

In Kotlin, Java static methods are called using the class name followed by the method name, like JavaClass.print().

What does Kotlin treat Java types as regarding nullability?

A Platform types with no enforced null-safety

B Always non-null

C Always nullable

D Ignored types

Kotlin treats Java types as platform types, meaning it does not enforce null-safety and you must handle nulls yourself.

How does Kotlin access Java getters?

A As Kotlin properties without get prefix

B Only by calling getMethod() explicitly

C Using Java reflection

D Cannot access Java getters

Kotlin treats Java getters as properties, so you can access them like normal Kotlin properties.

Which annotation helps Kotlin understand Java nullability?

A @Override

B @Nullable

C @Deprecated

D @SuppressWarnings

@Nullable and @NotNull annotations help Kotlin know if a Java value can be null or not.

If a Java method returns a nullable type but has no annotations, how does Kotlin treat it?

A As always nullable

B As non-nullable

C As a platform type with unknown nullability

D As an error

Without annotations, Kotlin treats Java types as platform types, meaning nullability is unknown and must be handled carefully.

Explain how Kotlin handles calling Java methods and properties seamlessly.

Think about how Kotlin treats Java code as if it were Kotlin code.

Describe the role of nullability annotations in Java when called from Kotlin.

Consider how Kotlin knows if a Java value can be null or not.