rspec/rules/S3215/java/rule.adoc

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

----
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.

----
static void EntryPoint(IMyInterface interfaceRef)
{
  Object o = (Object)interfaceRef;
  ...
}
----