Removing the "first" object from a Set

Question

Under certain situations, I need to evict the oldest element in a Java Set. The set is implemented using a LinkedHashSet, which makes this simple: just get rid of the first element returned by the set's iterator:

Set<Foo> mySet = new LinkedHashSet<Foo>(); // do stuff... if (mySet.size() >= MAX_SET_SIZE) {     Iterator<Foo> iter = mySet.iterator();     iter.next();     iter.remove(); } 

This is ugly: 3 lines to do something I could do with 1 line if I was using a SortedSet (for other reasons, a SortedSet is not an option here):

if (/*stuff*/) {     mySet.remove(mySet.first()); } 

So is there a cleaner way of doing this, without:

• changing the Set implementation, or
• writing a static utility method?

Any solutions leveraging Guava are fine.

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_{I am fully aware that sets do not have inherent ordering. I'm asking about removing the first entry as defined by iteration order.}

Answer 1

LinkedHashSet is a wrapper for LinkedHashMap which supports a simple "remove oldest" policy. To use it as a Set you can do

Set<String> set = Collections.newSetFromMap(new LinkedHashMap<String, Boolean>(){     protected boolean removeEldestEntry(Map.Entry<String, Boolean> eldest) {         return size() > MAX_ENTRIES;     } });