chore(Java): add priority queue array (#575)

algorithms/Java/README.md

@@ -27,6 +27,7 @@
 ## Queues
 - [Circular Queue using Linked List](queues/circular-queue-linked-list.java)
 - [Queue using Linked List](queues/queue-linked-list.java)
+- [Priority Queue using Array](queues/priority-queue-array.java)
 
 ## Scheduling
 - [Multi-Level Queue Scheduling](scheduling/multi-level-queue-scheduling.java)

algorithms/Java/queues/priority-queue-array.java

@@ -0,0 +1,78 @@
+// Class implementation of Priority-Queue using an array
+
+import java.util.*;
+
+
+class PriorityQueue {      
+	private int max_size;     // To provide maximum size of Array
+	private int[] arr;
+	private int no_items;
+
+	public PriorityQueue(int s){
+		max_size = s;
+		arr = new int[max_size];
+		no_items = 0;
+	}
+
+	public void insert(int val){   //Method to insert element into Priority Queue
+
+		int j;
+		if (no_items == 0){
+			arr[no_items++] = val;
+		}
+		else {
+
+			for ( j=no_items-1;j>=0;j--){
+
+				if (val<arr[j])    // To get in ascending order change to '>' operator
+				{
+					arr[j+1] = arr[j];
+				}
+				else break;
+
+			}
+
+			arr[j+1] = val;
+			no_items++;
+		}
+
+	}
+	public void remove(){      // Method to remove front element in Priority Queue
+		--no_items;
+	}
+
+	public int front(){          // Method to retrieve front element
+		return arr[no_items-1];
+	}
+
+	public boolean isEmpty() {   // Method to check if queue is empty
+		return no_items == 0;
+	}
+	public boolean isFull() {    // Method to check if queue is full
+		return no_items == max_size;
+	}
+
+
+}
+
+class Main {   // Class containing main method.
+
+	public static void main(String[] args) {
+		PriorityQueue pq = new PriorityQueue(5);
+		pq.insert(23);                     // [23]
+		pq.insert(56);                     // [56,23]
+		pq.insert(25);                     // [56,25,23]
+		System.out.println(pq.front());    // 56
+		pq.remove();                       // [25,23]
+		System.out.println(pq.front());    // 25
+		System.out.println(pq.isEmpty());  // False
+		pq.insert(100);                    // [100,25,23]
+		pq.insert(98);                     // [100,98,25,23]
+		pq.insert(99);                     // [100,99,98,25,23]
+		System.out.println(pq.front());    // 100
+		System.out.println(pq.isFull());   // True
+
+		
+	}
+
+}