The Iterator pattern in Java is equivalent to IEnumerable in .NET. Classes that were directly ported in Java using the Iterator pattern, cannot be used with Linq or foreach blocks in .NET.
Next() would be equivalent to .NET's MoveNext(), and in the below case, Term() would be as .NET's Current property. In cases as below, it will require TermEnum to become an abstract class with Term and DocFreq properties, which would be returned from another class or method that implemented IEnumerable<TermEnum>.
would instead look something like:
Keep in mind that it is important that if the class being converted implements IDisposable, the class that is enumerating the terms (in this case TermEnum) should inherit from both IEnumerable<T> and IDisposable. This won't be any change to the user, as the compiler automatically calls IDisposable when used in a foreach loop.