#### Priority Queues

R
```package com.thealgorithms.datastructures.queues;

/**
* This class implements a PriorityQueue.
*
* <p>
* A priority queue adds elements into positions based on their priority. So the
* most important elements are placed at the front/on the top. In this example I
* give numbers that are bigger, a higher priority. Queues in theory have no
* fixed size but when using an array implementation it does.
*/
class PriorityQueue {

/**
* The max size of the queue
*/
private int maxSize;
/**
* The array for the queue
*/
private int[] queueArray;
/**
* How many items are in the queue
*/
private int nItems;

/**
* Constructor
*
* @param size Size of the queue
*/
public PriorityQueue(int size) {
maxSize = size;
queueArray = new int[size];
nItems = 0;
}

/**
* Inserts an element in it's appropriate place
*
* @param value Value to be inserted
*/
public void insert(int value) {
if (isFull()) {
throw new RuntimeException("Queue is full");
} else {
int j = nItems - 1; // index of last element
while (j >= 0 && queueArray[j] > value) {
queueArray[j + 1] = queueArray[j]; // Shifts every element up to make room for insertion
j--;
}
queueArray[j + 1] = value; // Once the correct position is found the value is inserted
nItems++;
}
}

/**
* Remove the element from the front of the queue
*
* @return The element removed
*/
public int remove() {
return queueArray[--nItems];
}

/**
* Checks what's at the front of the queue
*
* @return element at the front of the queue
*/
public int peek() {
return queueArray[nItems - 1];
}

/**
* Returns true if the queue is empty
*
* @return true if the queue is empty
*/
public boolean isEmpty() {
return (nItems == 0);
}

/**
* Returns true if the queue is full
*
* @return true if the queue is full
*/
public boolean isFull() {
return (nItems == maxSize);
}

/**
* Returns the number of elements in the queue
*
* @return number of elements in the queue
*/
public int getSize() {
return nItems;
}
}

/**
* This class implements the PriorityQueue class above.
*
* @author Unknown
*/
public class PriorityQueues {

/**
* Main method
*
* @param args Command Line Arguments
*/
public static void main(String[] args) {
PriorityQueue myQueue = new PriorityQueue(4);
myQueue.insert(10);
myQueue.insert(2);
myQueue.insert(5);
myQueue.insert(3);
// [2, 3, 5, 10] Here higher numbers have higher priority, so they are on the top

for (int i = 3; i >= 0; i--) {
System.out.print(
myQueue.remove() + " "); // will print the queue in reverse order [10, 5, 3, 2]
}
// As you can see, a Priority Queue can be used as a sorting algotithm
}
}
```  