Question

Design a Java class named StringQueue for storing strings of first names into a queue.

The StringQueue.java class contains:

* A String[] data field named names that stores the String values in the queue.

* A private data field named size that stores the number of names in the queue.

* A public static final data field named DEFAULT_CAPACITY = 10 for the array.

* A private static data field named firstInitCtr that counts the number of names with the same first initial as your first initial.

* A StringQueue no-arg constructor that uses this(DEFAULT_CAPACITY) to construct an object with the default capacity for the string array.

* A StringQueue constructor that receives a new capacity to construct an object with the new capacity for the queue. The new capacity cannot be larger than the default capacity, and cannot be less than 1.

* The method enqueue(String value) that adds value into the queue.

* The method dequeue() that returns the first name from the queue and then shifts the remaining names in the queue to the left.

* The method empty() that returns true if the queue is empty.

* The method getSize() that returns the size of the queue.

* The method checkFirstInit(char firstInit) that adds 1 to the firstInitCtr if the name begins with your first initial.

* The method getFirstInitCtr() that returns the number of names with the same first initial as your name in the queue.

Write a test program called TestStringQueue.java that gets Scanner input for your first name, the number of first names in your queue (indicate the maximum is 10), and then ask for the names to populate the queue using the enqueue method. Invoke the checkFirstInit method to see if the first initial is the same as your first initial, and if so, increment the firstInitCtr. The first initial can either be in upper or lower case for it to be equal. Then, print out the names using the dequeue method. Finally, print out the number of names that begin with your first initial.

Sample runs:

Please enter your first name: joe

Please enter the number of names in your array. Maximum is 10: 11

Please enter the number of names in your array. Maximum is 10: 0

Please enter the number of names in your array. Maximum is 10: 5

Please enter 5 names for the queue: jim John ben carol Joe

Names dequeued:

jim John ben carol Joe

The number of names with your first initial is 3

Please enter your first name: Dan

Please enter the number of names in your array. Maximum is 10: 3

Please enter 3 names for the queue: sam dave ed

Names dequeued:

sam dave ed

The number of names with your first initial is 1

Answer 1

//StringQueue.java

public class StringQueue {
  
   private String[] names;
   private int size;
   public static int DEFAULT_CAPACITY = 10;
   private static int firstInitCtr =0;

   // default constructor
   public StringQueue()
   {
       this(DEFAULT_CAPACITY);
   }
  
   // parameterized constructor
   public StringQueue(int capacity)
   {
       // check if capacity is atleast 1 and atmost DEFAULT_CAPACITY, else set it to DEFAULT_CAPACITY
       if(capacity >=1 && capacity <=DEFAULT_CAPACITY)
       {
           names = new String[capacity];
       }else
           names = new String[DEFAULT_CAPACITY];
       size = 0;
   }
  
   // method to insert value at the end of the queue
   public void enqueue(String value)
   {
       // if queue is not empty,insert at the end and increment the size
       if(size < names.length)
       {
           names[size] = value;
           size++;
       }
   }
  
   // method to delete and return the front element of the queue
   public String dequeue()
   {
       // if queue is not empty
       if(!empty())
       {
           String data = names[0]; // get the first name of the queue
           // shift the elements to the left
           for(int i=0;i<size-1;i++)
           {
               names[i] = names[i+1];
           }
           size--; // decrement the size
          
           return data;
       }
      
       return null; // empty queue
   }
  
   // method that checks and returns if the queue is empty or not
   public boolean empty()
   {
       return(size == 0);
   }
  
   // method to return number of elements in the queue
   public int getSize()
   {
       return size;
   }
  
   // method to count the number of names with the same first initial as passed parameter, firstInit
   public void checkFirstInit(char firstInit)
   {
       // loop over the array
       for(int i=0;i<size;i++)
           // check if name at index i starts with firstInit, then increment the firstInitCtr
           if(names[i].toLowerCase().startsWith((firstInit+"").toLowerCase()))
               firstInitCtr++;
   }
  
   // method to return the firstInitCtr
   public int getFirstInitCtr()
   {
       return firstInitCtr;
   }
  
}
//end of StringQueue.java

//TestStringQueue.java

import java.util.Scanner;

public class TestStringQueue {
  
   public static void main(String[] args) {

      
       Scanner scan = new Scanner(System.in);
       String name;
       int capacity;
       // input of first name of the user
       System.out.print("Please enter your first name: ");
       name = scan.next();
       // input of capacity of the queue
       System.out.print("Please enter the number of names in your array. Maximum is "+StringQueue.DEFAULT_CAPACITY +": ");
       capacity = scan.nextInt();
       // validate and re-prompt until valid
       while(capacity < 1 || capacity > StringQueue.DEFAULT_CAPACITY)
       {
           System.out.print("Please enter the number of names in your array. Maximum is "+StringQueue.DEFAULT_CAPACITY +": ");
           capacity = scan.nextInt();
       }
       // create a queue of capacity
       StringQueue queue = new StringQueue(capacity);
      
       // input capacity number of names from user and insert into the queue
       System.out.print("Please enter "+capacity+" names for the queue : ");
       for(int i=0;i<capacity;i++)
           queue.enqueue(scan.next());
       // count the number of elements in queue with the same firstInitial as user's
       queue.checkFirstInit(name.charAt(0));
       // dequeue the elements of the queue until empty and display the names
       System.out.println("Names dequeued:");
       while(!queue.empty())
           System.out.print(queue.dequeue()+" ");
       System.out.println();
       // display the number of names with the same first initial as user
       System.out.println("The number of names with your first initial is "+queue.getFirstInitCtr());
       scan.close();
   }

}
//end of TestStringQueue.java

Output: