Question

programming language: JAVA

4. For this question, write code fragments or methods as directed. (a) Create the Point class that depends on a generic data type parameter T. It has two instance variables called xCoordinate and yCoordinate that both have type T. Write a two parameter constructor to initialize the instance variables. Answer: (b) Write a main method that has instructions to perform the following tasks (in order): Declare an ArrayList of Strings called carModels. Add three models. Print the size of the list. Remove the model from index 1. Insert a model at index 0. Replace the model at index 2. Answer: (c) Write a main method with a try-catch block. Inside the block it creates an array of Strings — the array is called list and has size 10. Print the value stored in list[10]. The catch block should catch ArithmeticException and RuntimeException. Your code shouldn’t be longer than 9 lines excluding curly braces. Answer: (d) Write the private method inputCircles that is called by the following main method. As- sume that class Circle exists and has constructors and a toString method. Your method should open a Scanner and obtain a radius for each of the 20 circles that you make from the user. (You should assume that the class Scanner has already been imported.) public static void main(String args[]) { Circle[] data = new Circle[20]; inputCircles(data); for (Circle c:data) System.out.println(c); } Answer:

Answer 1

(a)
//Point.java
/*Generic Point class of data type T
* The constructor takes two generic
* types,T and then set x and y values
* to x coordinate and ycoordinate*/
public class Point<T>
{
   private T xCoordinate;
   private T yCoordinate;
   /*constructor */
   public Point(T x, T y)
   {
       xCoordinate=x;
       yCoordinate=y;
   }
} //end of Point class

------------------------------------------------------------------------------------------------

(b)
import java.util.ArrayList;
public class Exercise_2
{
   public static void main(String[] args)
   {
       //Declare an ArrayList of Strings called carModels.
       ArrayList<String>carModels=new ArrayList<String>();
       //Add three models.
       carModels.add("Tata");
       carModels.add("Ferari");
       carModels.add("Maruthi");
       //Print the size of the list.
       System.out.println("Size of the carModels list : "+carModels.size());
       //Remove the model from index 1.
       carModels.ensureCapacity(1);
       //Insert a model at index 0.
       carModels.set(0,"Kia");
       //Replace the model at index 2.
       carModels.set(2, "Ford");
   }
}

------------------------------------------------------------------------------------------------

(c)

//Java program that demonstrates the (c) bit
//Exercise_3.java
public class Exercise_3
{
   public static void main(String[] args)
   {
       //Inside the block it creates an array of Strings
       String list[]=null;
       try
       {
           //the array is called list and has size 10.
           list=new String[10];
           //Print the value stored in list[10].
           for (int i = 0; i < list.length; i++)
               System.out.println(list[i]);          
       }
       //The catch block should catch ArithmeticException and RuntimeException.
       catch (ArithmeticException e)
       {
           System.out.println(e.getMessage());
       }
       catch (RuntimeException e)
       {
           System.out.println(e.getMessage());
       }
   }
}

Sample Output:
null
null
null
null
null
null
null
null
null
null

------------------------------------------------------------------------------------------------
(d)
//Circle.java
public class Circle
{
   private int radius;
   /*constructor*/
   public Circle()
   {
       radius=0;
   }
   /*constructor with radius*/
   public Circle(int r)
   {
       radius=r;
   }
   //set radius
   public void setRadius(int radius)
   {
       this.radius=radius;
   }
   //return radius as string
   public String toString()
   {  
       return String.format("Radius: %d", radius);
   }
}

/*Java program to demonstrate the Circle class
* in below program .
* Program prompt user to enter 20 radius values
* and the print the user enter values on console*/
//Exercise_4.java
import java.util.Scanner;
public class Exercise_4
{
   public static void main(String[] args)
   {
       //create an array of Circle class of size,20
       Circle[] data = new Circle[20];
       //calling inputCircles
       inputCircles(data);
       //print the circle objects
       for (Circle c:data)
           System.out.println(c);
   }

   private static void inputCircles(Circle[] data)
   {
       Scanner console=new Scanner(System.in);
       for (int r = 0; r < data.length; r++)
       {
           System.out.printf("Enter radius,r :");
           int radius=Integer.parseInt(console.nextLine());
           data[r]=new Circle(radius);
       }
   }
}

Sample output:

Enter radius,r :1
Enter radius,r :2
Enter radius,r :3
Enter radius,r :4
Enter radius,r :5
Enter radius,r :6
Enter radius,r :7
Enter radius,r :8
Enter radius,r :9
Enter radius,r :10
Enter radius,r :11
Enter radius,r :12
Enter radius,r :13
Enter radius,r :14
Enter radius,r :15
Enter radius,r :16
Enter radius,r :17
Enter radius,r :18
Enter radius,r :19
Enter radius,r :20
Radius: 1
Radius: 2
Radius: 3
Radius: 4
Radius: 5
Radius: 6
Radius: 7
Radius: 8
Radius: 9
Radius: 10
Radius: 11
Radius: 12
Radius: 13
Radius: 14
Radius: 15
Radius: 16
Radius: 17
Radius: 18
Radius: 19
Radius: 20