What it says on the package. For example, in NetworkRegistry there is a private member called "chatListeners" and there is a way to add to it (registerChatListener) but no way to remove from it. unregisterChatListener would take a listener and simply remove it by value. Though this would really have negligable effect on performance over just setting a "ignoreEverything" flag on the listener itself, I think it's a more concise way to manage listeners for all sorts of messages (not just chat). Plus when debugging or adding status monitors in the future, there wouldn't be a lot of (internally dead) listeners cluttering up the list.

 

Should be trivial to implement in most cases, if a bit of busywork. I might do it myself later on github.

Use reflection: Make a method in one of your classes to set the member accessible and then remove from it. I've done that:

public static void removeChatListener(int index)
{
try
{
	Field f = NetworkRegistry.class.getDeclaredField("chatListeners");
	f.setAccessible(true);
	List<IChatListener> list = (List<IChatListener>) f.get(NetworkRegistry.instance());
	if(list.get(index) != null)
	{
		IChatListener c = list.get(index);
		System.out.println("Removed chat listener " + c);
		list.remove(index);
	}
}
catch(Exception e)
{
	System.err.println("Tried to remove chat listener " + index + " but it didn't work! ):");
	e.printStackTrace();
}
}

Alternatively, you can change int index to be a Class object, assuming you know the exact class of the listener you're trying to remove. IE:

public static void removeChatListener(Class listener)
{
try
{
	Field f = NetworkRegistry.class.getDeclaredField("chatListeners");
	f.setAccessible(true);
	List<IChatListener> list = (List<IChatListener>) f.get(NetworkRegistry.instance());
	for(int i = 0; i < list.size(); i++)
	{
		IChatListener check = list.get(i);
		if(check.getClass() == listener)
		{
			System.out.println("Removed chat listener " + check);
			list.remove(check);
		}
	}
}
catch(Exception e)
{
	System.out.println("Tried to remove a chat listener but it didn't work. ):");
	e.printStackTrace();
}
}