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COMP 202 Lecture Notes - Lecture 21: Programming Paradigm

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rosealligator817
25 Oct 2016
School
McGill University
Department
Computer Science (Sci)
Course
COMP 202
Professor
Melanie Lyman- Abramovitch

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There are 850 students in the class. int numstudents = 850. String[] firstnames = new string[numstudents]; everyone has a first name. Everyone has a last name. long [] ids = new long[numstudents]; Everyone has an email. double[] gpa = new double[numstudents]; We need to make all these arrays to make a list of all these students. Not great because: (1) this is a lot of arrays. Bulky. (2) there"s nothing here explicitly linking the first name of a student in firstnames to the last name of the same student in lastnames. Hopefully, the index should link them together, but if someone makes a mistake anywhere, it will get all messed up. Objects are a reference type and we"ve already used some. This means that java allows you to write your own data type using object oriented programming (oop) . This means we can create our own data types, of type object, essentially.

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Related Questions

8. Write a class called WordSet representing a set of String objects which can contain an arbitrary number of strings, limited only by the memory available to the Java Virtual Machine. A set is a collection of elements, however, unlike a list, a set cannot contain duplicate elements. Therefore, as its name implies, a WordSet object cannot contain duplicate Strings that is, if one attempts to da String to a Wordset, and the wordset already contains an element which is equal to this string, the attempt will fail and the state of the Wordset will not change. All String comparisons performed in the methods defined in the Wordset class are done in a Case SENSITIVE manner. Note that in the method descriptions below, the phrase "this Wordset" means "the Wordset on which the method in question is called." Your Wordset class MUST provide the following INSTANCE methods • A constructor, which takes no parameters and initializes the new Wordset ohject so that it contains no elements • A method called add(), which takes as its only parameter a string and returns a value of type boolean. If this Wordset already contains a string which is equal to the parameter string, or the parameter String is null, then the state of this Wordset does not change and the method return false; otherwise, the parameter String is added to this Wordset. and the method returns true. • A method called remove().which takes as its only parameter a string and returns a value of type boolean. If this wordSet contains a string which is equal to the parameter String this string is removed from the WordSet and the method returns true. On the other hand, if the string parameter is null or this Wordset does not contain a string which is equal to the parameter string, then the state of this wordset does not change, and the method return false. • A method called get.size(), which takes no parameters and returns the number of strings currently stored in this Wordset. This method MUST NOT change the state of this Wordset. • A method called isMember(). which takes as its only parameter a string and retumsa value of type boolean which is true if this wordset contains the parameter String false otherwise. If the parameter String is null, this method also return false. This method MUST NOT change the state of this wordset. • A method called computebirrerence().which takes as its only parameter a Wordset and returns a new Wordset representing the difference between this wordset and the parameter Wordset: in other words, the WordSet returned by this method contains all the strings that are in this wordset, but not in the parameter Wordset. If the parameter Wordset contains all the elements of this WordSet or this WordSet contains no elements, then this method returns a new Wordset containing no elements. Finally, if the parameter Wordset is null or contains ne strings, then this method returns a new wordset which contains all the elements of this wordset. This method MUST NOT change the state of this wordset or the parameter Wordset. • A method called tostring , which takes the parameters and turns a string which is the textual representation of this wordset. This textual representation consists of the concatena tion of the following clements - The String - The text representation of each clement in the WordSet; cach pair of adjacent clements is separated by the String", but this String MUST NOT appear before the first clement or after the last element - The String") The order in which the elements of this Wordset appear in the textual representation generated by the tostring() method does not matter. If the WordSet contains to Brings, then the textual representation returned by this method is ". Note that you MUST respect proper encapsulation practices that is, the attributes and methods of your class MUST be declared using the proper visibility modifier NINT Um an array list (of string) to keep track of the string stored in a wordt ob joot Is there a method defined in the Array loist class which determines whether in clementis already wored in an array ist, and which will do a case-sensitive comparison when liked on an Arraylint of strings? See the pages 24-26 of this examination for information about potentially useful methods defined by the ArrayList class WRITE YOUR Wordset CLASS IN THE SPACE BELOW:

7. Write a class MetroLine in which you define a new type MetroLine (10 points) A MetroLine is defined to have the following private properties: • A String representing the colour of the line (e.g. blue, red, green, etc. No numbers. It's Montreal, not Manhattan!) • A collection of MetroStation This collection can be either a built in array, an ArrayList, or any other kind of collection you feel would satisfy the requirements of the class. The collection must be able to define an ordering from "beginning" to "end" of the MetroLine. It does not matter which part you consider the beginning and which part is the "end" as long as it is consistent. (We recommend using ArrayList but you are free to do otherwise if you feel it will be casier.) A MetroLine should have the following methods defined: • A constructor which takes nothing as input and performs any initialization necessary to maintain your collection of stations. • A method addstation which takes as input a MetroStation and adds it to the end of your collection. The method can assume the station is not already part of the collection and should return void. Note that the order the MetroStations are added is the same as the path the trains will travel on (or it could be the reverse path as well). • A method hasStation which takes as input a MetroStation and returns a boolean representing whether the metro line has a MetroStation with the same name or not. A method get LineColour which returns the colour of the line. • A method get First Stop which returns the MetroStation representing the first stop of the metro line. If there is no such station (ic, if the collection of MetroStation is empty), your method should return null. • A method get PriorStop which takes as input a MetroStation and returns the stop prior to the MetroStation passed as input. You may assume that the MetroStation passed as input is indeed in the collection of MetroStations If the current station is the first stop on the MetroLine then this method should return null. You may assume that there are no "loops" in the MetroLine That is, no station is present on the same line twice. A method getNext Stop which takes as input a MetroStation and returns the stop after the MetroStation passed as input. You may assume that the Metrostation passed as input is indeed in the collection of Metrostations. If the current station is the last stop on the MetroLine, then this method should return null. You may assume that there are no "loops" in the MetroLine That is, no station is present on the same line twice. For the above methods, you may assume that there is no aliasing issue. That is to say, you can use == to compare the references, or if you are using a type such as ArrayList to maintain your list of stations, you can use the indexOf or contains method defined on an ArrayList.