Question

I had some very wrong sounding advice recently from a “senior” developer/coworker regarding the C# garbage collector such as…

• “You need to use destructors
  everywhere in C# because the garbage
  collector cannot be relied upon.”

• “The C# garbage collector cannot be
  thought of like the Java garbage
  collector”.

This sounds extremely fishy to me, as far as I know the differences between the C# and Java garbage collectors are as follows…

• The C# is a Generational garbage
  collector, Java is concurrent mark
  sweep in 1.6 with G1 being the new
  default (generational) garbage
  collector featuring Java 7 and has
  been optional since ~1.6.21. As far
  as I know
• C# as a language has the ability to
  manually dispose of objects that
  implement IDisposable. Java must
  always use garbage collection,
  although some frameworks like SWT
  require you manually call methods to
  release memory in the underlying
  native code.

I realize that Java and C# are just the languages and the garbage collectors are a component of the runtime, however for this case I am specifically speaking about the Sun/Oracle JVM and the Microsoft .NET Runtime.

Does anybody have feedback?

Answer 1

The advice you’ve been given is, broadly speaking, a load of hooey.

Both C# and Java have GCs that attempt to optimise the fast recovery of lots of small objects. They’re designed to solve the same problem, they do it in slightly different ways but as a user the technical differences in your approach to using them is minimal, even non-existent for the majority of users.

IDisposable is nothing to do with the GC as such. It’s a standard way of naming methods that would otherwise be called close, destroy, dispose, etc., and often are called that in Java. There is a proposal for Java 7 to add something very similar to the using keyword that would call a similar close method.

“Destructors” in C# refers to finalizers – this was done deliberately to confuse C++ programmers. 🙂 The CLR spec itself calls them finalizers, exactly as the JVM does.

There are many ways in which Java and C#/CLR differ (user value types, properties, generics and the whole family of related features known as Linq), but the GC is one area where you can develop a substantial amount of software before you need to worry much about the difference between them.