On this page:
Problem 1: Abstracting over Data Definitions
Problem 2: Working with Custom Constructors, A Taste of Equality
Problem 3: Trigrams

Assignment 3: Abstracting over Data Definitions; Custom constructors; Accumulators

Goals: Learn to use the String class, practice working with lists. Learn to design methods for complex class hierarchies.


This assignment is long. Start early.

Be very, very careful with naming! Again, the solution files expect your submissions to be named a certain way, so that they can define their own Examples class with which to test your code. Therefore, whenever the assignment specifies:
  • the names of classes,

  • the names and types of the fields within classes,

  • the names, types and order of the arguments to the constructor,

  • the names, types and order of arguments to methods, or

  • filenames,

...be sure that your submission uses exactly those names.

Make sure you follow the style guidelines that Bottlenose enforces. For now the most important ones are: using spaces instead of tabs, indenting by 2 characters, following the naming conventions (data type names start with a capital letter, names of fields and methods start with a lower case letter), and having spaces before curly braces.

You will submit this assignment by the deadline using the Bottlenose submission system. You may submit as many times as you wish. Be aware of the fact that close to the deadline the system may have a long queue of submissions which means it takes longer for your code to be submitted - so try to finish early.

The submission will be organized as follows:

Due dates:
  • Tuesday, February 8th at 9:00pm

Problem 1: Abstracting over Data Definitions

Related files:

In this problem, our data will represent different kinds of media. Each piece of media has a title and list of available languages for captions. Different kinds of media can also contain additional information as shown in the supplied Media.java file.

Note: none of these methods are properly implemented. As given in the file, they are all stubs that currently return a dummy value, so the code will compile but not yet work.

Warmup: Download the file and work out the following problems:

Once you have finished these methods and are confident that they work properly, save the work you have done to a separate file. Do not submit the code as written so far. The problems below are the main point of this exercise, and it will be helpful for you to preserve the code written so far as a reference against which to compare your revised code below. Again, submit only the work below.

Submit your work in a file named Media.java.

Problem 2: Working with Custom Constructors, A Taste of Equality

A BagelRecipe can be represented as the amount of flour, water, yeast, salt, and malt in the recipe. A perfect bagel results when the ratios of the weights are right:

Design the BagelRecipe class. The fields should be of type double and represent the weight of the ingredients as ounces. Provide three constructors for this class:

Flour and water volumes are measured in cups, while yeast, salt, and malt volumes are measured in teaspoons.

Helpful conversion factors:
  • 48 teaspoons = 1 cup

  • 1 cup of yeast = 5 ounces

  • 1 cup of salt = 10 ounces

  • 1 cup of malt = 11 ounces

  • 1 cup of water = 8 ounces

  • 1 cup of flour = 4 and 1⁄4 ounces

You should use an IllegalArgumentException with a helpful message if the above constraints cannot be enforced.

Once you’ve completed the above constructors, you should:
  • Remove as much duplicate code as possible from these constructors.

  • Implement the method sameRecipe(BagelRecipe other) which returns true if the same ingredients have the same weights to within 0.001 ounces.

Submit your work in a file named Bagel.java.

Problem 3: Trigrams

Technically, this is a word-level trigram. There are also letter-level trigrams, which are simply three-letter sequences. The generalized version of these are called \(n\)-grams.

A trigram is a three-word phrase, such as “three word phrase”. Trigrams are often used in machine-learning and search applications, to find documents matching a given search phrase, or to summarize a document by its most common terms.

You will likely need several helper methods for this assignment. Be sure to test your code thoroughly. Hint: you will need to use one or more accumulators on this problem. Be sure to clearly explain their meaning in an accumulator statement, which should be written just beneath the purpose statement, just as we did in Fundies 1.

Submit your work in a file named Trigrams.java.