Homework #1 - Java Basics

Homework #1

Note : Submit Emails to : sdlabuofk@gmail.com  (The Email in the printed Lab Sheet was wrong ! sorry)

Deadline is : 15 OCT 2016 11:59 PM

Part #1 Coding Exercises (7 Marks)

1.  (3 Marks) Write a program that reads in a series of first names and eliminates duplicates by storing them in a Set. Allow the user to search for a first name by implementing a proper function for that 

2.  (4 Marks) (This Exercise is almost solved with below codes given)  The code below Defines an integer stack interface_: 

interface IntStack

   {

    void push(int item); // store an item 
    int pop(); // retrieve an item

    }

Create a class called FixedStack that implements IntStack above , FixedStack class has two variables ( tos (index to the current top of stack from type int , and integer array stck as in below ) , Complete the implementation of this class  so it can represent a stack with a fixed size

class FixedStack implements IntStack

{

    private int stck[];     
    private int tos;

    FixedStack(int size)

    {

    /*Add your code here to implement the constructor that   initialize                 both fixed stck array and tos */

    }

    public void push(int item)

    {

 /* Add your code here to implement Push Function that adds an integer   element to the stack (Take in consideration when user trying to add to a full stack */

    }

    public int pop()

    {

 /* Add your code here to implement Pop Function that pops item from stack

(Take in consideration the this is a fixed size stack */

    }

       Then test your class with below code in MAIN as below:

    public static void main(String args[])

    {

        FixedStack mystack1 = new FixedStack(5);

        FixedStack mystack2 = new FixedStack(8);         // push some numbers onto the stack         for(int i=0; i<5; i++) mystack1.push(i);         for(int i=0; i<8; i++) mystack2.push(i);         // pop those numbers off the stack         System.out.println("Stack in mystack1:")         for(int i=0; i<5; i++)

            System.out.println(mystack1.pop());

1

        System.out.println("Stack in mystack2:")         for(int i=0; i<8; i++)

            System.out.println(mystack2.pop());

    }

Part #2 Short Questions (3 Marks)

•       What is wrong with the following interface?

public interface SomethingWrongWithThisInterface {

    void aMethod() {

        System.out.println("Hi,You’ve Just called aMethod");

    }

}

•       Fix the interface above?

•       Is the following interface valid?

public interface Student {

 }

Part #3 BONUS “OPTIONAL” (5 Marks)

One of most known and simple design patterns in industry is the singleton pattern. This design pattern restricts the instantiation of a class to one object , so it’s useful when exactly one object is needed to coordinate actions across the system. Knowing the concept of “static” keyword in java show how can you implement a single class which is responsible to create an object while making sure that only single object gets created. This class provides a way to access its only object which can be accessed directly without need to instantiate the object of the class. (Write Code Example)

In what Applications do you think that this design pattern suits, why?

Submission Guidelines:

•       Subject of Email Should be : Java_HW(No)_(Index)  E.g.  Java_HW1_104048

•       Submit Java Files .java for codes and document (.doc,.docx,.pdf) for short questions (As we’re using automatic filters for downloading attachments then answers in email body will not be received so make sure that all your answers are in attachment)

•       Bonus must be submitted in Separate file (either .Java or document file )

2