Create a Queue interface

• Creation of an interface for character queues.

• Three implementations to be developed:

• Fixed size linear queue.

• Circular queue (reuses array space).

• Dynamic queue (grows as needed).

1 Create a file called ICharQ.java
// Character queue interface.
public interface ICharQ {
// Inserts a character into the queue.
void put(char ch);
// Remove a character from the queue.
char get();
}

2 Create a file called IQDemo.java.

3 Start creating IQDemo.java by adding the FixedQueue class shown here:

4 Add the CircularQueue class shown below to IQDemo.java.

• Circular Queue Operation: Reuses space freed up in the array when removing elements. It can store an unlimited number of elements, as long as there are removals.

• Boundary Conditions: The queue is not full when the end of the array is reached, but when an unremoved item is overwritten by a new one.
  The put() method must check several conditions to determine whether the queue is full.

• Conditions for Full Queue: The queue is full if: putloc is a smaller unit than getloc. putloc is at the end of the array and getloc is at the beginning.

• Empty Queue Condition: The queue is empty when getloc and putloc are equal.

• Array Size: The underlying array is created one unit larger than the queue size to facilitate checks.

5 Insert the DynQueue class shown below in IQDemo.java. It implements an “extendable” queue that expands its size when space runs out.

• In this queue implementation, when the queue is full, an attempt to store another element makes a new underlying array twice as large as the original will be allocated, the current contents of the queue will be copied into this array and a reference to the new array will be stored in q.

6 To demonstrate the three implementations of ICharQ, insert the following class into IQDemo.java. It uses an ICharQ reference to access all queues.

class IQDemo {
public static void main(String args[]) {
FixedQueue q1 = new FixedQueue(10);
DynQueue q2 = new DynQueue(5);
CircularQueue q3 = new CircularQueue(10);
ICharQ iQ;
char ch;
int i;
iQ = q1;
// Inserts some characters into the fixed queue.
for(i=0; i < 10; i )
iQ.put((char) ('A' i));
// Displays the queue.
System.out.print("Contents of fixed queue: ");
for(i=0; i < 10; i ) {
ch = iQ.get();
System.out.print(ch);
}
System.out.println();
iQ = q2;
// Inserts some characters into the dynamic queue.
for(i=0; i < 10; i )
iQ.put((char) ('Z' - i));
// Displays the queue.
System.out.print("Contents of dynamic queue: ");
for(i=0; i < 10; i ) {
ch = iQ.get();
System.out.print(ch);
}
System.out.println();
iQ = q3;
// Inserts some characters into the circular queue.
for(i=0; i < 10; i )
iQ.put((char) ('A' i));
// Displays the queue.
System.out.print("Contents of circular queue: ");
for(i=0; i < 10; i ) {
ch = iQ.get();
System.out.print(ch);
}
System.out.println();
// Inserts more characters into the circular queue.
for(i=10; i < 20; i )
iQ.put((char) ('A' i));
// Displays the queue.
System.out.print("Contents of circular queue: ");
for(i=0; i < 10; i ) {
ch = iQ.get();
System.out.print(ch);
}
System.out.println("nStore and consume from"
" circular queue.");
// Stores and consumes items from the circular queue.
for(i=0; i < 20; i ) {
iQ.put((char) ('A' i));
ch = iQ.get();
System.out.print(ch);
}
}
}

7 Create a circular version of DynQueue. Add a reset( ) method to ICharQ that nets the queue. Create a static method that copies the contents of one queue type to another.

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