Hash Maps Solution

In this homework, you will implement a key-value hash map with a quadratic probing collision policy. A hash map maps keys to values and allows O(1) average case lookup of a value when the key is known. This hash map must be backed by an array of initial size 11, and must be resized to have a size of 2n + 1 when the table exceeds (greater than, not greater than or equal to) a load factor of 0.67. These values are provided as constants in the interface, and the constants should be used within your code.




The table should not add duplicate keys, but duplicate values are acceptable. In the event of a duplicate key, replace the existing value with the new value.




Neither keys nor values may be null.




Hash Functions




You should not write your own hash functions for this assignment; use the hashCode() method (every Object has one). If this is a negative value, use the absolute value of the hash code (and then mod by the table length).




Quadratic Probing




Your hash map must implement a quadratic probing collision policy. If the hash value of the key is occupied, probe in quadratic increments. For example, if the hash value of your key is 3 with a backing array of size 9, and index 3 in the array is occupied, check index 3 + 12 mod 9, then 3 + 22 mod 9, then 3 + 32 mod 9, etc.




Adding Items




When adding a key/value pair to a hash map, add the pair to the next available slot, starting at the computed index. Remember that available slots include both null and items marked as removed. Also remember that keys are unique in a hash map, so you must ensure that duplicate keys are not added.







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Homework 6: Hash Maps Due: See T-Square










If no available slots are found after table.length number of probes, regrow the array and begin probing from the initial hashed index.




Grading




Here is the grading breakdown for the assignment. There are various deductions not listed that are incurred when breaking the rules listed in this PDF, and in other various circumstances.




Methods:






put
17pts




remove
18pts




get
10pts




containsKey
10pts




keySet
5pts




values
5pts




resizeBackingTable
5pts




clear
5pts




Other:






Checkstyle
10pts




E ciency
15pts




Total:
100pts







Keep in mind that add functions are necessary to test other functions, so if an add doesn't work, remove tests might fail as the items to be removed were not added correctly. Additionally, the size function is used many times throughout the tests, so if the size isn't updated correctly or the method itself doesn't work, many tests can fail.




A note on JUnits




We have provided a very basic set of tests for your code, in HashMapStudentTests.java. These tests do not guarantee the correctness of your code (by any measure), nor does it guarantee you any grade. You may additionally post your own set of tests for others to use on the Georgia Tech GitHub as a gist. Do NOT post your tests on the public GitHub. There will be a link to the Georgia Tech GitHub as well as a list of JUnits other students have posted on the class Piazza.




If you need help on running JUnits, there is a guide, available on T-Square under Resources, to help you run JUnits on the command line or in IntelliJ.




Style and Formatting




It is important that your code is not only functional but is also written clearly and with good style. We will be checking your code against a style checker that we are providing. It is located in T-Square, under Resources, along with instructions on how to use it. We will take o a point for every style error that occurs. If you feel like what you wrote is in accordance with good style but still sets o the style checker please email Raymond Ortiz (rortiz9@gatech.edu) with the subject header of \CheckStyle XML".




Javadocs




Javadoc any helper methods you create in a style similar to the existing Javadocs. If a method is overridden or implemented from a superclass or an interface, you may use @Override instead of writing Javadocs.
















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Homework 6: Hash Maps Due: See T-Square










Exceptions




When throwing exceptions, you must include a message by passing in a String as a parameter. The mes-sage must be useful and tell the user what went wrong. \Error", \BAD THING HAPPENED", and \fail" are not good messages. The name of the exception itself is not a good message.




For example:




throw new PDFReadException("Did not read PDF, will lose points.");




throw new IllegalArgumentException("Cannot insert null data into data structure.");




Generics




If available, use the generic type of the class; do not use the raw type of the class. For example, use new LinkedList<Integer() instead of new LinkedList(). Using the raw type of the class will result in a penalty.




Forbidden Statements




You may not use these in your code at any time in CS 1332.




break may only be used in switch-case statements




continue package




System.arraycopy() clone()




assert()




Arrays class Array class




Collections class




Collection.toArray()




Re ection APIs




Inner, nested, or private classes




Debug print statements are ne, but nothing should be printed when we run them. We expect clean runs - printing to the console when we're grading will result in a penalty. If you use these, we will take o points.




Provided




The following le(s) have been provided to you. There are several, but you will only edit one of them.




 
HashMapInterface.java




This is the interface you will implement in HashMap. All instructions for what the methods should do are in the javadocs. Do not alter this le.







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Homework 6: Hash Maps Due: See T-Square










 
HashMap.java




This is the class in which you will implement HashMapInterface. Feel free to add private helper methods but do not add any new public methods, inner/nested classes, instance vari-ables, or static variables.




 
MapEntry.java




This class stores a key-value pair and a removed attribute for your hash map. Do not alter this le.




 
HashMapStudentTests.java




This is the test class that contains a set of tests covering the basic operations on the HashMap class. It is not intended to be exhaustive and does not guarantee any type of grade. Write your own tests to ensure you cover all edge cases.







Deliverables




You must submit all of the following le(s). Please make sure the lename matches the lename(s) below, and that only the following le(s) are present. T-Square does not delete les from old uploads; you must do this manually. Failure to do so may result in a penalty.




After submitting, be sure you receive the con rmation email from T-Square, and then download your uploaded les to a new folder, copy over the interfaces, recompile, and run. It is your responsibility to re-test your submission and discover editing oddities, upload issues, etc.




 
HashMap.java










































































































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