iterating over TreeSet using Iterator and using enhanced for loop of Java 5. Here is our complete Java program which shows step by step guide to iterate over TreeSet in Java. Java Program to traverse over TreeSet in Java You can also remove the current element by calling the remove() method of Iterator, don't use the remove() method provided by the interface because that will result in ConcurrentModificationException as shown here. You can follow 3 steps to start iterating over TreeSet using Iterator, remember this is going from first to the last element in the sorted order.ġ) get the Iterator by calling the iterator() methodĢ) Use a for or while loop with hasNext() Iterating over TreeSet using Iterator Example Therefore, the iterator always visits the elements in sorted order. Every time an element is added to a tree, it is placed into its proper sorting position. I ntroduction to Algorithms By Thomas Cormen, Charles Leiserson, Ronald Rivest, and Clifford Stein. Heres a thought experiment for you to go through. If you think about how the computer has to reconcile it, it makes sense. For a detailed description of red-black trees, see a good algorithm book e.g. It is problematic to iterate over a list and remove elements while iterating over it. The current implementation of uses a Red-Black tree. The sorting is accomplished by a tree data structure. Using Iterators to remove elements from a Java Collection. Java - removing an element in list while iterating it with a for index loop. for (Iterator iter list.listIterator() iter.hasNext() ).Make sure your variable names are correct. You insert an element in any order but when you iterate through the collection, the values are automatically presented in the sorted order. Youre using iterator but you iterate this list using iter. In this article, you will find examples of both approaches.įor those who are new to TreeSet, A TreeSet is a sorted collection in Java. On the other hand, Iterator allows you to remove elements while iterating over TreeSet. You can also use the enhanced for loop, which also internally uses the Iterator and traverse the TreeSet in the same order, but you cannot remove an element there. When you iterate over a TreeSet the iterator follows this order. 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. 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. You can use both, enhanced for loop and Iterator to traverse over TreeSet in Java. 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.
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