It is a priority queue based on priority heap.
- add(element) : java.util.PriorityQueue.add() insert the elements to the Priority Queue. Syntax :
public boolean add(E e) Parameters : element : the element we need to add. Return : call return true. Exception : -> ClassCastException -> NullPointerException
- comparator() : java.util.PriorityQueue.comparator() orders the elements in the queue. Syntax :
public Comparator comparator() Parameters : ------- Return : orders the queue or return null, if it is naturally ordered Exception : ----------
- contains(Object obj) : java.util.PriorityQueue.contains(obj) returns true if the priority queue contains the element "obj". Syntax :
public boolean contains(Object obj) Parameters : obj : object to be checked Return : true - if the object is present else, return false Exception :
- iterator() : java.util.PriorityQueue.iterator() iterates over the queue element. Syntax :
public Iterator iterator() Parameters : ------- Return : calls iterator over the elements in the queue. Exception : --------
- offer(element) : java.util.PriorityQueue.offer() is required to insert a specific element to the given priority queue. Syntax :
public boolean offer(E element) Parameters : element : specific element to be entered. Return : call return true. Exception : -> ClassCastException -> NullPointerException
- peek() : java.util.PriorityQueue.peek() identifies the head element of the queue. Syntax :
public E peek() Parameters : ------- Return : calls if head exists, else null Exception : ------
- poll() : java.util.PriorityQueue.poll() identifies the head and then removes it. Syntax :
public E poll() Parameters : --- Return : calls if head exists, else null Exception : ------
- remove(Object obj) : java.util.PriorityQueue.remove() removes a specific object from the queue. Syntax :
public boolean remove(Object obj) Parameters : obj : object to be removed Return : true - if obj is removed Exception : ------
- size() : java.util.PriorityQueue.size() returns the size of elements in the Priority Queue. Syntax :
public int size() Parameters : ---- Return : no. of elements Exception : ---------
- toArray() : java.util.PriorityQueue.toArray() returns an array containing the elements of PriorityQueue. Syntax :
public Object[] toArray() Parameters : ------ Return : returns an array containing all the elements of PriorityQueue. Exception : --------
- toArray(T[] array) : java.util.PriorityQueue.toArray(T[] a) returns the array having the elements of the Priority Queue. Syntax :
public T[] toArray(T[] array) Parameters : array : the array to which are to be sorted. Return : call an array containing all the elements of the array. Exception : -> ArrayStoreException -> NullPointerException
- clear() : java.util.PriorityQueue.clear() clears all the elements of the PriorityQueue. Syntax :
public void clear() Parameters : --- Return : ------ Exception : ------
Java // Java Program illustrating the methods // of java.utl.priorityQueue class // add(), comparator(), conatins(), iterator(), offer() // peek(), poll(), toArray(), size(), toArray(t[] g1), // remove(), clear() import java.util.*; public class NewClass { public static void main(String[] args) { // Creating a Priority Queue : PriorityQueue <Integer> geek = new PriorityQueue <Integer> (); for(int i=2; i<=20; i=i+2) { // Use of add() : geek.add(new Integer (i)); } System.out.println("geek PriorityQueue : " + geek); // Use of comparator() // No ordering is required here as it is naturally ordered. Comparator geek_comp = geek.comparator(); System.out.println("geek PriorityQueue : " + geek_comp); // Use of contains() boolean check = geek.contains(6); System.out.println("Use of contains() : " + check); // Use of iterator() Iterator g_iterator = geek.iterator(); System.out.print("Iterator values : "); while(g_iterator.hasNext()) { System.out.print(g_iterator.next() + " "); } System.out.println(""); // Use of offer() geek.offer(3050); System.out.println("geek PriorityQueue : " + geek); // Use of peek() System.out.println("Head of PriorityQueue via peek : " + geek.peek()); //Use of poll() int h = geek.poll(); System.out.println("\nHead of PriorityQueue via poll : " + h); System.out.println("geek PriorityQueue bcz of poll() : " + geek); // Use of remove() boolean r = geek.remove(8); System.out.println("\nCan remove : " + r); System.out.println("geek PriorityQueue bcz of remove() : " + geek); // use of size() System.out.println("\nSize of PriorityQueue : " + geek.size()); // Use of toArray() Object[] g = geek.toArray(); System.out.print ( "Array from PriorityQueue : "); for ( int i = 0; i<g.length; i++ ) { System.out.print (g[i].toString() + " ") ; } System.out.println("\n"); // Use of toArray(t[] g1) : Integer[] g2 = new Integer[5]; Integer[] g1 = geek.toArray(g2); System.out.print ( "Array from PriorityQueue of size 5 : "); for ( int i = 0; i<g1.length; i++ ) { System.out.print (g1[i].toString() + " ") ; } System.out.println("\n"); // Use of clear() geek.clear(); System.out.println("PriorityQueue after clear() : " + geek); } } geek PriorityQueue : [2, 4, 6, 8, 10, 12, 14, 16, 18, 20] geek PriorityQueue : null Use of contains() : true Iterator values : 2 4 6 8 10 12 14 16 18 20 geek PriorityQueue : [2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 3050] Head of PriorityQueue via peek : 2 Head of PriorityQueue via poll : 2 geek PriorityQueue bcz of poll() : [4, 8, 6, 16, 10, 12, 14, 3050, 18, 20] Can remove : true geek PriorityQueue bcz of remove() : [4, 10, 6, 16, 20, 12, 14, 3050, 18] Size of PriorityQueue : 9 Array from PriorityQueue : 4 10 6 16 20 12 14 3050 18 Array from PriorityQueue of size 5 : 4 10 6 16 20 12 14 3050 18 PriorityQueue after clear() : []