I need to combine two string sets while filtering out redundant information, this is the solution I came up with, is there a better way that anyone can suggest? Perhaps something built in that I overlooked? Didn't have any luck with google.
Set<String> oldStringSet = getOldStringSet();
Set<String> newStringSet = getNewStringSet();
for(String currentString : oldStringSet)
{
if (!newStringSet.contains(currentString))
{
newStringSet.add(currentString);
}
}
Since a Set only contains one instance of a element. You can therefor combind the two by:
ReplyDeletenewStringSet.addAll(oldStringSet);
It does not matter if you add things twice, the set will only contain the element once... e.g it's no need to check using contains method.
Just use newStringSet.addAll(oldStringSet). No need to check for duplicates as the Set implementation does this already.
ReplyDeleteUse boolean addAll(Collection<? extends E> c)
ReplyDeleteAdds all of the elements in the specified collection to this set if they're not already present (optional operation). If the specified collection is also a set, the addAll operation effectively modifies this set so that its value is the union of the two sets. The behavior of this operation is undefined if the specified collection is modified while the operation is in progress.
newStringSet.addAll(oldStringSet)
From the definition Set contain only unique elements.
ReplyDeleteSet<String> distinct = new HashSet<String>();
distinct.addAll(oldStringSet);
distinct.addAll(newStringSet);
To enhance your code you may create a generic method for that
public static <T> Set<T> distinct(Collection<T>... lists) {
Set<T> distinct = new HashSet<T>();
for(Collection<T> list : lists) {
distinct.addAll(list);
}
return distinct;
}
http://docs.oracle.com/javase/7/docs/api/java/util/Set.html#addAll(java.util.Collection)
ReplyDeleteSince sets can't have duplicates, just adding all the elements of one to the other generates the correct union of the two.
Set.addAll()
ReplyDeleteAdds all of the elements in the specified collection to this set if they're not already present (optional operation). If the specified collection is also a set, the addAll operation effectively modifies this set so that its value is the union of the two sets
newStringSet.addAll(oldStringSet)
newStringSet.addAll(oldStringSet);
ReplyDeleteThis will produce Union of s1 and s2