Java - DukeJava - 4-3-2 Interface and Abstract Class

DukeJava - 4-3-2 Programming Exercise 2 Interface-and-Abstract-Class

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Java-Programming-and-Software-Engineering-Fundamentals-Specialization

• 4.Java-Programming-Principles-of-Software-Design
  • N-Grams: Predictive Text
    • 4-3-1 Programming Exercise 1 Generating Random Text
    • 4-3-2-Interface-and-Abstract-Class

Resource Link: https://www.dukelearntoprogram.com/course4/index.php ProjectCode: https://github.com/ocholuo/language/tree/master/0.project/javademo

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The class MarkovRunnerWithInterface for running your program to generate random text. This class has several methods:
    A void method named runModel that has three parameters: an IMarkovModel variable named markov, a String named text and an int named size. This method will work with any markov object that implements IMarkovModel.

    A void method named runMarkov. This method creates one of the types of Markov models, and calls runModel with it to generate random text.

    A void method named printOut that formats and prints the randomly generated text.


Two protected fields myText, a String, and myRandom, of type Random.
    A constructor that creates myRandom.

    A setTraining method that is public. This method sets the the private String variable myText to the parameter text.

    A signature for the abstract method getRandomText that has one integer parameter named numChars indicating the length of the randomly generated text.

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Assignment 1: IMarkovModel Interface

Copy over four of the .java files from the the work you did with the previous assignment. (You will need to keep a copy of the program you created from the first two assignments for testing.) Specifically you should copy over the four Java files: MarkovZero.java, MarkovOne.java, MarkovFour.java, and MarkovModel.java. You can ignore the following files from the previous lesson—MarkovRunner.java and Tester.java. We will modify the program to organize it in a different way, using an interface and an abstract class.

Modify your classes MarkovZero, MarkovOne, MarkovFour, and MarkovModel to implement the IMarkovModel interface. Each of these classes should already have the two required methods setTraining and getRandomText, so the only change needed is the first line to add: implements IMarkovModel

Run the method runMarkov that is in the MarkovRunnerWithInterface class. This method should run several Markov objects and generate random text for a MarkovZero, a MarkovOne, a MarkovModel with number 3, and a MarkovFour. Notice that runMarkov is called with each one of these. You can observe that the text gets more like the training text as you move from MarkovZero to MarkovFour.

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Assignment 2: AbstractMarkovModel Abstract Class

the AbstractMarkovModel abstract class need changes

The method getFollows you wrote is the same everywhere. move it into the AbstractMarkovModel class and change this method from public to protected.

Anything that is protected in AbstractMarkovModel should be deleted in the other files they are in. In each of MarkovZero, MarkovOne, MarkovFour and MarkovModel, delete the declarations of the two private variables myText and myRandom, and delete the getFollows method if it has one.

Each of MarkovZero, MarkovOne, MarkovFour, and MarkovModel need to change in their definition “implements IMarkovModel” to “extends AbstractMarkovModel”

Run the method runMarkov that is in the MarkovRunnerWithInterface class. It should run as before.
Notice that when you print any markov object, you get its name and an address location. These objects don’t know how to print themselves. Write a toString method, so each one prints out “MarkovModel of order n,” where n is the number. For example, a MarkovFour object should print out “MarkovModel of order 4.”

Modify your program so that you can set a seed in the runMarkov method in the MarkovRunnerWithInterface class and pass it to the runModel method (add a 4th parameter named seed) to set the random seed for any markov object. In the runModel class you should be able to set this seed with the line:
markov.setRandom(seed).

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Assignment 3: HashMap for Efficiency

Write a new class named EfficientMarkovModel (make a copy of MarkovModel to start with) that extends AbstractMarkovModel
and that builds a HashMap to calculate the follows ArrayList for each possible substring only once,
and then uses the HashMap to look at the list of characters following when it is needed.

This class should include:

a toString method to print that this is the EfficientMarkovModel class of a specific number

a method named buildMap to build the HashMap (Be sure to handle the case where there may not be a follow character. If that key is not in the HashMap yet, then it should be put in mapped to an empty ArrayList.) Think carefully about where to call this method, considering that you will want to build a map for each new training text.

a getFollows method, but this getFollows method should be much shorter, as it can look up the ArrayList of Strings, instead of computing it each time.


To test your HashMap to make sure it is built correctly, write the void method printHashMapInfo in the EfficientMarkovModel class. Make sure to call this method immediately after building the map. This method should print out the following information about the HashMap:

Print the HashMap (all the keys and their corresponding values). Only do this if the HashMap is small.
Print the number of keys in the HashMap
Print the size of the largest value in the HashMap—that is, the size of the largest ArrayList of characters
Print the keys that have the maximum size value.

Write a new method named testHashMap in the MarkovRunnerWithInterface class. This method should create an order-2 EfficientMarkovModel with

seed 42
the training text is “yes-this-is-a-thin-pretty-pink-thistle”
the size of the text generated is 50
Note that “le” occurs only once at the end of the training text

In the MarkovRunnerWithInterface class, call testHashMap. You should see that the HashMap has the following information:

It has 25 keys in the HashMap
The maximum number of keys following a key is 3
Keys that have the largest ArrayList (of size 3 in this case) are: “hi”, “s-”, “-t”, “is”, and “th”

After running it, you’ll probably want to comment out the call to printHashMapInfo in the EfficientMarkovModel class.
In the MarkovRunnerWithInterface class, create a void method named compareMethods that runs a MarkovModel and an EfficientMarkovModel. In particular,

Make both order-2 Markov models
Use seed 42 and set the length of text to generate to be 1000
Both should call runModel that generates random text three times for each.
Run the MarkovModel first and then the EfficientMarkovModel with the file “hawthorne.txt” as the training text. One of them should be noticeably faster. You can calculate the time each takes by using System.nanoTime() for the current time.

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