How to loop over a TreeSet in Java with Example

In our earlier articles, we have learned how to loop over ArrayList in Java and you can use the same logic to loop over a TreeSet. You can use both, enhanced for loop and Iterator to traverse over TreeSet in Java. Though worth noting is that Iterator returned by the iterator() method of TreeSet returns elements in the sorted order which is imposed by the Comparator you have provided to TreeSet at the time of instantiation. By default, if you don't provide any custom Comparator then TreeSet sorts elements in their natural order like String elements are sorted in alphabetical order and Integer elements are sorted in numeric order. When you iterate over a TreeSet the iterator follows this order.

How to Convert a List to a Set in Java with Example

How to convert a List to Set in Java

Many times we need to convert one collection to another like converting a List to a Set. It's also an easy way to copy contents from one collection to other in Java, like from List to Set or Set to List. Thanks to the Collection framework in Java, copying collections from one to another is extremely easy. Since every Collection class implements a Collection interface that defines the addAll() method, which can be used to create a collection from contents of another collection.

How to sort HashSet in Java? Example

Somebody asked me recently, how do you sort a HashSet? For lists, we use the Collections.sort(List) method, but there is nothing for Set. If I have a HashSet then how would I go about sorting it? The answer is you cannot sort a HashSet, why? because HashSet is an unordered collection. When you insert an element in HashSet then you lose the order guarantee. You cannot do reordering or sorting in Set because it does not have random access methods (ie, .get() an element at a given index), which is basically required for sort algorithms.

Difference between HashSet and TreeSet in Java

Difference between HashSet and TreeSet in Java

There are several differences between a HashSet and a TreeSet are similar to what we discussed as a difference between TreeMap and HashMap. Anyway, Set and Map are two completely different interfaces so we will revisit those differences here. Probably the most important difference between HashSet and TreeSet is the performance. HashSet is faster than TreeSet which means if you need performance use HashSet but HashSet doesn't provide any kind of ordering so if you need ordering then you need to switch to TreeSet which provides sorting of keys.