Question

Convert the Queue to Generic implementation:

public class MyQueueImpl implements MyQueue {
   private int capacity;
   private int front;
   private int rear;
   private int[] arr;
   public MyQueueImpl(int capacity){
       this.capacity = capacity;
       this.front = 0;
       this.rear = -1;
       this.arr = new int[this.capacity];
   }
   @Override
   public boolean enQueue(int v) {      
           if(this.rear == this.capacity - 1) {
               //Perform shift
               int tempSize = this.size();
               for(int i=0; i < tempSize; i++) {
                   arr[i] = arr[front];
                   front++;
               }
               front = 0;
               rear = tempSize - 1;
           }
           this.rear ++;
           arr[rear] = v;
           return true;
   }
   @Override
   public int deQueue() {
       return arr[front++];
      
   }
   public String toString() {
       String content = "Queue :: ";
      
       for(int i=front; i<= rear; i++) {
           content += "\n" + arr[i];
       }
       return content;
   }
   @Override
   public boolean isFull() {
       return (this.size() == this.capacity);
   }
   @Override
   public int size() {
       return rear - front + 1;
   }
   @Override
   public boolean isEmpty() {
       // TODO Auto-generated method stub
       return (this.size() == 0);
   }
   @Override
   public int peek() {
       // TODO Auto-generated method stub
       return this.arr[this.front];
   }
}

Answer 1

Short Summary:

• Converted the MyQueueImpl class to implement generics.
• We cannot create generic type array inside the MyQueueImpl class in JAVA. So, have to use generic ArrayList instead of array.
• Shown you the test driver class and sample run

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Source Code:

MyQueue.java File:

public interface MyQueue<E> {
   public boolean enQueue(E v);
   public E deQueue();
   public boolean isFull();
   public int size();
   public boolean isEmpty();
   public E peek();
}

MyQueueImpl.java File:

import java.util.ArrayList;

public class MyQueueImpl<E> implements MyQueue<E> {
   private int capacity;
   private int front;
   private int rear;
   private ArrayList<E> arr;

   public MyQueueImpl(int capacity) {
       this.capacity = capacity;
       this.front = 0;
       this.rear = -1;
       this.arr = new ArrayList<E>();
   }

   @Override
   public boolean enQueue(E v) {
       if (this.rear == this.capacity - 1) {
           // Perform shift
           int tempSize = this.size();
           for (int i = 0; i < tempSize; i++) {
               arr.add(i, arr.get(front));
               front++;
           }
           front = 0;
           rear = tempSize - 1;
       }
       this.rear++;
       arr.add(rear, v);
       return true;
   }

   @Override
   public E deQueue() {
       return arr.get(front++);

   }

   public String toString() {
       String content = "Queue :: ";

       for (int i = front; i <= rear; i++) {
           content += "\n" + arr.get(i);
       }
       return content;
   }

   @Override
   public boolean isFull() {
       return (this.size() == this.capacity);
   }

   @Override
   public int size() {
       return rear - front + 1;
   }

   @Override
   public boolean isEmpty() {
       // TODO Auto-generated method stub
       return (this.size() == 0);
   }

   @Override
   public E peek() {
       // TODO Auto-generated method stub
       return this.arr.get(this.front);
   }
}

GenericQueueTest.java File:
public class GenericQueueTest {

   public static void main(String[] args) {
      
       // IntegerQueue
       MyQueueImpl<Integer> intQueue = new MyQueueImpl<Integer>(10);
       intQueue.enQueue(10);
       intQueue.enQueue(20);
       intQueue.enQueue(30);
       intQueue.enQueue(40);
       intQueue.enQueue(50);
       System.out.println("Integer Queue: \n" + intQueue.toString());
       System.out.println("Integer Queue Peek: " + intQueue.peek());
       while(!intQueue.isEmpty()) {
           System.out.println("Integer Dequeued: " + intQueue.deQueue());
       }
      
       // IntegerQueue
       System.out.print("\n\n\n");
       MyQueueImpl<String> stringQueue = new MyQueueImpl<String>(10);
       stringQueue.enQueue("Java");
       stringQueue.enQueue("Generics");
       stringQueue.enQueue("Programming");
       stringQueue.enQueue("is");
       stringQueue.enQueue("Fun");
       System.out.println("String Queue: \n" + stringQueue.toString());
       System.out.println("String Queue Peek: " + stringQueue.peek());
       while(!stringQueue.isEmpty()) {
           System.out.println("String Dequeued: " + stringQueue.deQueue());
       }

   }

}

Sample Run: