how to iterate over a priority queue using collections in java
how to iterate over a priority queue using collections in java
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In this example we shall see how can we iterate over the elements of a PriorityQueue using the Iterator interface.
For creating a PriorityQueue first of all we have to import the java.util package in which the java.util.PriorityQueue class is defined. In this example we have created a class named CollectionsExample in which we created an object of the PriorityQueue and added some elements to the queue.
In this example we have used the iterator() method on the object of the PriorityQueue. By using this method we can traverse all the elements of the PriorityQueue.
In the given example we have, created a PriorityQueue object pq and added some elements to it by using the add(Object obj) method on it. Then we have invoked the iterator() method on the pq and stored the values in the Iterator reference itr, then we have invoked the hasNext() of the Iterator interface on the itr and then displayed the values of the pq by using the next() method on the itr.
package r4r.co.in;
import java.util.*;
public class CollectionsExample {
/**
* @param args
*/
public static void main(String[] args) throws NullPointerException, ClassCastException
{
// TODO Auto-generated method stub
try
{
PriorityQueue<Integer> pq=new PriorityQueue<Integer>(); // creating a PriorityQueue of Integer type
pq.add(1); // adding element to the queue
pq.add(2);
pq.add(3);
pq.add(4);
pq.add(5);
System.out.println("The contents of the PriorityQueue are: "+pq); // displaying the elements of the queue
Iterator<Integer> itr=pq.iterator(); // invoking iterator on the priority queue object
System.out.println("The elements in the priority queue are: ");
while(itr.hasNext())
{
System.out.println(itr.next()); // displaying the queue elements
}
}
catch(NullPointerException e)
{
e.printStackTrace();
}
catch(ClassCastException e)
{
e.printStackTrace();
}
}
}
The output of the above given example is :
The contents of the PriorityQueue are: [1, 2, 3, 4, 5]
The elements in the priority queue are:
1
2
3
4
5
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