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Priority Queue Operations
Introduction to Priority Queues
A priority queue is a special type of queue in which each element is associated with a priority, and elements are served based on their priority. Higher priority elements are dequeued before lower priority ones.
Use Cases of Priority Queues
Priority queues are widely used in applications like CPU scheduling, Dijkstra's shortest path algorithm, and bandwidth management.
Example 1: Basic Priority Queue
import java.util.PriorityQueue;
public class BasicPriorityQueue {
public static void main(String[] args) {
PriorityQueue pq = new PriorityQueue<>();
pq.add(4);
pq.add(2);
pq.add(5);
System.out.println("Priority Queue: " + pq);
}
}
Example 2: Custom Comparator
import java.util.PriorityQueue;
import java.util.Comparator;
public class CustomComparator {
public static void main(String[] args) {
PriorityQueue pq = new PriorityQueue<>(Comparator.reverseOrder());
pq.add(4);
pq.add(2);
pq.add(5);
System.out.println("Priority Queue (Descending): " + pq);
}
}
Example 3: String Priority Queue
import java.util.PriorityQueue;
public class StringPriorityQueue {
public static void main(String[] args) {
PriorityQueue pq = new PriorityQueue<>();
pq.add("Apple");
pq.add("Banana");
pq.add("Cherry");
System.out.println("String Priority Queue: " + pq);
}
}
Example 4: Removing Elements
import java.util.PriorityQueue;
public class RemoveElements {
public static void main(String[] args) {
PriorityQueue pq = new PriorityQueue<>();
pq.add(4);
pq.add(2);
pq.add(5);
System.out.println("Removed Element: " + pq.poll());
System.out.println("Priority Queue after removal: " + pq);
}
}
Example 5: Peek Operation
import java.util.PriorityQueue;
public class PeekOperation {
public static void main(String[] args) {
PriorityQueue pq = new PriorityQueue<>();
pq.add(4);
pq.add(2);
pq.add(5);
System.out.println("Peek Element: " + pq.peek());
}
}
Example 6: Priority Queue with Objects
import java.util.PriorityQueue;
import java.util.Comparator;
class Student {
String name;
int grade;
public Student(String name, int grade) {
this.name = name;
this.grade = grade;
}
@Override
public String toString() {
return name + ": " + grade;
}
}
public class ObjectPriorityQueue {
public static void main(String[] args) {
PriorityQueue pq = new PriorityQueue<>(Comparator.comparingInt(s -> s.grade));
pq.add(new Student("Alice", 85));
pq.add(new Student("Bob", 90));
pq.add(new Student("Charlie", 80));
System.out.println("Student Priority Queue: " + pq);
}
}
Example 7: Checking if Empty
import java.util.PriorityQueue;
public class CheckIfEmpty {
public static void main(String[] args) {
PriorityQueue pq = new PriorityQueue<>();
System.out.println("Is the Priority Queue empty? " + pq.isEmpty());
pq.add(4);
System.out.println("Is the Priority Queue empty after adding an element? " + pq.isEmpty());
}
}
Example 8: Iterating Through Priority Queue
import java.util.PriorityQueue;
public class IteratePriorityQueue {
public static void main(String[] args) {
PriorityQueue pq = new PriorityQueue<>();
pq.add(4);
pq.add(2);
pq.add(5);
System.out.println("Iterating through Priority Queue:");
for (Integer num : pq) {
System.out.println(num);
}
}
}
Example 9: Clearing the Priority Queue
import java.util.PriorityQueue;
public class ClearPriorityQueue {
public static void main(String[] args) {
PriorityQueue pq = new PriorityQueue<>();
pq.add(4);
pq.add(2);
pq.add(5);
pq.clear();
System.out.println("Priority Queue after clearing: " + pq);
}
}
Example 10: Size of Priority Queue
import java.util.PriorityQueue;
public class SizeOfPriorityQueue {
public static void main(String[] args) {
PriorityQueue pq = new PriorityQueue<>();
pq.add(4);
pq.add(2);
pq.add(5);
System.out.println("Size of Priority Queue: " + pq.size());
}
}
