What will happen if Java code accesses an internal field declared in Kotlin?

From the JVM perspective, the internal field in Kotlin is compiled into a private field with a generated JVM name that includes the class name, property name, and a hash. If you try to access this field directly from Java code using the original Kotlin field name, the Java compiler will produce an error because this field is not accessible.

However, the Kotlin compiler generates getters and setters for internal fields, which have public visibility at the JVM level. The names of these methods follow the convention: get<PropertyName> and set<PropertyName>. You can call these getters and setters from Java code to access the internal field.

Example of a Kotlin class with an internal field:

class KotlinClass {
    internal var internalProperty: String = "default"
}

Example Java code accessing this field:

// Not directly accessible
// kotlinClass.internalProperty = "new value"; // Compilation error in Java

KotlinClass kotlinClass = new KotlinClass();
// Access via generated getter and setter
kotlinClass.setInternalProperty("new value from Java");
String value = kotlinClass.getInternalProperty();