What is PriorityQueue or priority queue data structure in Java with Example - Tutorial
PriorityQueue is an unbounded Queue implementation in Java, which is based on priority heap. PriorityQueue allows you to keep elements in a particular order, according to there natural order or custom order defined by Comparator interface in Java. Head of priority queue data structure will always contain least element with respect to specified ordering
PriorityQueue in Java is that it's Iterator doesn't guarantee any order, if you want to traverse in ordered fashion, better use Arrays.sort(pq.toArray()) method. PriorityQueue is also not synchronized, which means can not be shared safely between multiple threads, instead it's concurrent counterpart PriorityBlockingQueue is thread-safe and should be used in multithreaded environment. Priority queue provides O(log(n)) time performance for common enqueing and dequeing methods e.g. offer(), poll() and add(), but constant time for retrieval methods e.g. peek() and element().
PriorityQueue keeps least value element at head, where ordering is determined using compareTo() method. It doesn't keep all elements in that order though, only head being least value element is guaranteed. This is in fact main difference between TreeSet and PriorityQueue in Java, former keeps all elements in a particular sorted order, while priority queue only keeps head in sorted order. Another important point to note is that PriorityQueue doesn't permit null elements and trying to add null elements will result in NullPointerException.
Read full article from What is PriorityQueue or priority queue data structure in Java with Example - Tutorial
PriorityQueue is an unbounded Queue implementation in Java, which is based on priority heap. PriorityQueue allows you to keep elements in a particular order, according to there natural order or custom order defined by Comparator interface in Java. Head of priority queue data structure will always contain least element with respect to specified ordering
PriorityQueue in Java is that it's Iterator doesn't guarantee any order, if you want to traverse in ordered fashion, better use Arrays.sort(pq.toArray()) method. PriorityQueue is also not synchronized, which means can not be shared safely between multiple threads, instead it's concurrent counterpart PriorityBlockingQueue is thread-safe and should be used in multithreaded environment. Priority queue provides O(log(n)) time performance for common enqueing and dequeing methods e.g. offer(), poll() and add(), but constant time for retrieval methods e.g. peek() and element().
PriorityQueue keeps least value element at head, where ordering is determined using compareTo() method. It doesn't keep all elements in that order though, only head being least value element is guaranteed. This is in fact main difference between TreeSet and PriorityQueue in Java, former keeps all elements in a particular sorted order, while priority queue only keeps head in sorted order. Another important point to note is that PriorityQueue doesn't permit null elements and trying to add null elements will result in NullPointerException.
Read full article from What is PriorityQueue or priority queue data structure in Java with Example - Tutorial
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