Topdown v BottomupConventions in Compsci 100(e) projectsMVC Example, MarkovKWIC main program/classModel View Controller, MVCConvention SummaryMethods, Interfaces, InheritanceInterfaces continuedCompsci 100e7.1Topdown v BottomupProgramming is changing our worldEmpowering, liberating, equalizing,…Everything is a bit: all 0’s and 1’sFrom jpg to mp3 to …It’s about problems! It’s about details!Should we think about problems to get to the details?Should we master details before grand thinking?See Wikipedia on topdown v bottomup designCompsci 100e7.2Conventions in Compsci 100(e) projectsWe want you to concentrate on algorithms and data structuresNot on rendering fonts, interacting with usersThis is important! But not what this course is aboutWe try to build GUIs or views that facilitate projectsYou write the brains, we build the skull/manikinOur GUI communicates with your code•Requires following conventions in interacting codeGUI libraries are similar across languages, but…Deeper Java specific details than HashMapCompsci 100e7.3MVC Example, MarkovUser loads fileWhere? Communicate to?What changes in model?What happens in view?User chooses wordProcess in ModelAlternatives?Generate context, displayHow to show in any view?ModelinitializeaddViewprocess------fillMapjustifySimpleViewshowMessageshowErrorupdateaddModelCompsci 100e7.4KWIC main program/classpublic class MarkovMain { public static void main(String[] args){ IModel model = new MarkovModel(); SimpleViewer view = new SimpleViewer("Compsci 100e Markov", ”k count>"); view.setModel(model); }} What changes in above, e.g., for other assignments?How can view communicate with any model?View doesn’t change, model does!•Requires using a Java interface to capture commonalityCompsci 100e7.5Model View Controller, MVCGui is the View and often the controllerSeparate user-interaction from updates to dataUser loads file, chooses word, …Model notified, computes, updates viewModel has all the state and knows when it changesCommunicates changes to views (via controller)Must be initialized, updated, etc.Very common Design PatternCapture common solutions to problems in a contextIterator, Composite, Decorator seen in Compsci 100eCompsci 100e7.6Convention SummaryClasses start with capital letter and then we have:They’re public, except nested class? Protected means …camelCaseForMethods and ForClassesIvars, fields, instance variables, mySize, myMap, …Constants (public static) are ALL_CAPSInterfaces are IModel, IView, and so onNot true for standard Java classes, yes for Compsci 100Don’t need to label methods as abstract, but canSupply AbstractDefault implements IThingConstructor, some state, some common behavior: extend!Compsci 100e7.7Methods, Interfaces, InheritanceA method by any other name would smell as sweetMethod in OO languages, functions, procedures in othersParameters and return value: communication•Do objects or methods communicate?: OO v proceduralStatic : Math.sqrt, Character.isUpperCase, …Don’t belong to an object, invoked via class (clue above?)Java API helpful hereInterface: implement class with required, related methodsHashMap, TreeMapArrayList, LinkedList, VectorCompsci 100e7.8Interfaces continuedIn the beginningMake code work, don’t worry about generalizingBut, if you write code using Map rather than TreeMap•Can swap in a new implementation, coded generally!Don’t know how to optimize: space or timeFacilitate change: use interface rather than concrete classMy DVD connects to my TV, regardless of brand, why?How do you turn on a Nokia cell phone? Motorola? But!Interfaces facilitate code refactoringDon’t add functionality, change speed or memory or
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