Java- Homework 1 Solved

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Introduction to Interfaces
Throughout this course, we will use interfaces to provide the requirements for the code you'll be required to write. An interface specifies a list of methods that any class implementing it must provide. In this assignment, we will provide you with an interface for each class you need to implement. This means that any class you write must have implementations of every method that its interface specifies, otherwise it won't compile!

For more detail on interfaces, see the Oracle documentation.

Problem 1 
Define a Rectangle class (in Rectangle.java) that implements RectangleInterface. In addition, you should implement the Comparable interface, such that Rectangle objects can be compared by their perimeter. That is, your class signature should be:

public class Rectangle implements RectangleInterface, Comparable<Rectangle>

You must have this class signature for full credit.

Finally, you must have a constructor that takes in doubles of the length and width as parameters:

public Rectangle(double length, double width) 

As is implied by the parameters to the constructor, your instance variables should also be doubles.

Problem 2
Write a GenericMethods class (in GenericMethods.java) that implements GenericMethodsInterface.

There are two methods you must implement:

linearSearch: Iterate through the array linearly and search for a value equal (again, in the Comparable sense) to x. This must run in O(n) time. If the value is not found in the array, return -1. Else, return the index in the array where the value was found.
binarySearch: Implement a recursive binary search to find a value equal to x. Hint: The public binarySearch method, itself, should not be recursive. The private helper method should be. This private helper method with additional parameters should be called from the public binarySearch method. This must run in O(log n) time. If the value is not found in the array, return -1. Else, return the index in the array where the value was found.
To test your code, you might try creating a file with a main method that does the following:

Build an array of Rectangle objects
Demonstrate linearSearch functionality on the array
Sort the array with Arrays.sort (remember, input to binarySearch must be sorted)
Demonstrate binarySearch functionality on the array
This is not required, but will be useful if you're looking for ways to guarantee your implementation is correct.

Your GenericMethods class must implement the interface for full credit.

Problem 3 
In a file called BigO.java, implement BigOInterface and write methods that have the following runtime requirements:

cubic must be O(n^3)
exp must be O(2^n)
constant must be O(1)
Where n is an integer which is passed into the function. The methods can contain any code fragments of your choice. However, in order to receive any credit, the runtime requirements must be satisfied. As in the previous two problems, you must implement the interface to receive full credit.

In addition to writing the code fragments, we will explore their actual runtimes, to observe big-O in action in the real world. In a file called Problem3.java write a main method which runs the code with various values of n and measures their runtime. Then, discuss the results you observed briefly in a file called Problem3.txt.

Please run each of your methods with multiple different values of n and include the elapsed time for each of these runs and the corresponding value of n in Problem3.txt.

To properly time code runtime in Java, we must disable compiler optimizations. We do this by running the code with the -Xint flag, for example: java -Xint Problem3. The easiest way to time your run is to wrap each fragment with the following code:

long startTime = System.nanoTime();
// YOUR CODE HERE
long endTime = System.nanoTime();

The elapsed time is the difference between these two variables.