Build and use your own minimal queue class using an array of type String of fixe
ID: 3806651 • Letter: B
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;
Please notice that this must be done using an array not an arraylist or any other list, I think im close but am having trouble with a couple things, Thanks
Explanation / Answer
PROGRAM:
package queue;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
public class Queue
{
private double[] queue=new double[5];
private int size=5;
private int front=0;
private int rear=0;
public Queue()
{
}
//Parameterized constructor for initializing array size
public Queue(int size)
{
this.queue = new double[size];
this.front = 0;
this.rear=0;
this.size = size;
}
//inserting values in to queue
public void enQueue(double obj)
{
rear = (rear + 1) % queue.length;
if (rear == front)
{ //if full
System.out.println("Queue is fully loaded.");
if (rear == 0)
rear = queue.length - 1;
else
rear = rear - 1;
return;
}
queue[rear] = obj;
}
//checking whether queue is empty
public boolean isEmpty()
{
if(this.front==-1 && this.rear==-1)
{
return true;
}
return false;
}
// //checking whether queue is full
public boolean isFull()
{
if(rear==0 && front==size-1)
{
return true;
}
return false;
}
//entering the values from the queue
public double deQueue()
{
if (rear == front) {//if empty
System.out.println("Queue is empty.");
return -1;
}
double tmp = queue[front+1];
front = (front+1) % queue.length;
return tmp;
}
//main function
public static void main(String s[]) throws NumberFormatException, IOException
{
//variable type queue
Queue q1= null;
//InputStreamReader & BufferedReader for reading the input
InputStreamReader in=new InputStreamReader(System.in);
BufferedReader br=new BufferedReader(in);
int choice=0;
double number=0;
System.out.println("1. user default size of array:");
System.out.println("2. custum size");
choice=Integer.parseInt(br.readLine().toString());
//checking user is using default size of an array or customized size
if(choice==1)
{
q1=new Queue();
}
else if(choice==2)
{
System.out.println(" enter size of array:");
int size=Integer.parseInt(br.readLine());
q1=new Queue(size);
}
loop:do
{
System.out.println("1. Enqueur");
System.out.println("2. Dequeue");
System.out.println("3. is empty");
System.out.println("4. is full");
System.out.println("5. exit");
System.out.println("Enter the Choice:");
choice=Integer.parseInt(br.readLine());
switch(choice)
{
case 1:
//pushing the value to the queue
try
{
System.out.println("Enter the number:");
number=Double.parseDouble(br.readLine());
q1.enQueue(number);
}
catch(IndexOutOfBoundsException e)
{
System.out.println("Array is full");
}
break;
case 2:
//poping the value from the queue
System.out.println(q1.deQueue());
break;
case 3:
//checking the queue whether it is empty or not
System.out.println(q1.isEmpty());
break;
case 4:
//checking the queue whether it is full or not
System.out.println(q1.isFull());
break;
case 5:
break loop;
default:
System.out.println("Enter a valid choice");
}
}while(true);
}
}
OUTPUT
1. user default size of array:
2. custum size
1
1. Enqueur
2. Dequeue
3. is empty
4. is full
5. exit
Enter the Choice:
1
Enter the number:
2
1. Enqueur
2. Dequeue
3. is empty
4. is full
5. exit
Enter the Choice:
2
2.0
1. Enqueur
2. Dequeue
3. is empty
4. is full
5. exit
Enter the Choice:
1
Enter the number:
1
1. Enqueur
2. Dequeue
3. is empty
4. is full
5. exit
Enter the Choice:
1
Enter the number:
1
1. Enqueur
2. Dequeue
3. is empty
4. is full
5. exit
Enter the Choice:
3
false
1. Enqueur
2. Dequeue
3. is empty
4. is full
5. exit
Enter the Choice:
4
false
1. Enqueur
2. Dequeue
3. is empty
4. is full
5. exit
Enter the Choice:
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