Build and use your own minimal queue class using an array of type String of fixe

Question

Build and use your own minimal queue class using an array of type String of fixed size to hold the queue.

The array should have the default size of 5.

The array size should be setable via a constructor.

The following methods must be implemented:

enqueue – inserts a value at the rear of the queue

dequeue – returns the value at the front of the queue, removing the value from the queue

isEmpty – returns true if the queue is empty, false otherwise

isFull - – returns true if the queue is full, false otherwise

Tip: In a queue of 2 or more elements, the index of the rear is “larger” than the index of the front – EXCEPT, the queue will need to “wrap around” the array. For example: If the array is 20 elements. the queue front is at index 15 and the queue rear is at index 19, the next enqueue will be at index 20, which doesn't exist. The index must “wrap around” the array, i. e. the next enqueue will be at index 0. The solution is to modulus by the array size whenever increasing an index, either rear of front. For example, to change the index of the rear to the next index,use the formula

rear = (rear + 1) % arraySize;

Explanation / Answer

Lets start implementing queue via circular queue.

Now,In queue we have to maintain two pointers front say f and rear say r. Front will point to the first(index 1) element i.e. head of the queue and dequeue operation will be happened from front pointer whereas Rear pointer will point at the last indexed element and enqueue will happen at rear.

Now for your understanding, lets write pseudo code first. Here r=rear,f=front, N=arraysize.

isFull() : if( r - f == -1 || N-1) then

return true

else return flase

isempty(): if(r==f) then

return true.

enqueue() :

if(usFull()) then

throw someuserdefinedQueueexception

else

Queue[r] = stringobj

r = (r+1) mod N

So lets start implementing in JAVA.

Step1) Make an Interface "Queue"

Step2) Write the exceptions

Step3) Write java class to implement the queue interface that we wrote in step1

Step 4:) Write class to test all this above classes.

Note, put all the above classes in same package, its a good practice.

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