rspec/rules/S3215/java/rule.adoc

== Why is this an issue?

Needing to cast from an ``++interface++`` to a concrete type indicates that something is wrong with the abstractions in use, likely that something is missing from the ``++interface++``. Instead of casting to a discrete type, the missing functionality should be added to the ``++interface++``. Otherwise there is the risk of runtime exceptions.

=== Noncompliant code example

[source,java]
----
public interface MyInterface {
  void doStuff();
}

public class MyClass1 implements MyInterface {
  int data;
  public void DoStuff()  {
    // TODO...
  }
}

public static class DowncastExampleProgram {
  static void EntryPoint(MyInterface interfaceRef) {
    MyClass1 class1 = (MyClass1)interfaceRef;  // Noncompliant
    int privateData = class1.data;
  }
}
----

=== Exceptions

Casting to ``++Object++`` doesn't raise an issue, because it can never fail.

[source,java]
----
static void EntryPoint(IMyInterface interfaceRef)
{
  Object o = (Object)interfaceRef;
  ...
}
----

ifdef::env-github,rspecator-view[]

'''
== Implementation Specification
(visible only on this page)

include::../message.adoc[]

'''
== Comments And Links
(visible only on this page)

include::../comments-and-links.adoc[]

endif::env-github,rspecator-view[]