CS 280 Data Structures

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CS 280Data Structures

• Professor John Peterson

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Netbeans Magic

• What you did on Project 2 can be done much more
  easily if you use the refactoring menu on
  NetBeans.
• Rename Sortable to SortableArrayInt or
  something like that. This is done by
  rightclicking the class name and going to
  refactor -gt rename. When you see the preview of
  the changes, uncheck the edit on the argument to
  the sort in main.
• Right click on the definition of SortableArrayInt
  and go to refector, then select extract
  interface. Name the extracted interface
  Sortable. Accept all changes.

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Abstractions

• When we have general classes of objects that all
  do something similar, we want to use different
  sorts of objects interchangeably.
• The main way of doing this with Java is an
  interface. This allows us to choose any class
  that implements the interface when we need a
  value denoted by the interface.
• Review how do interfaces work?

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Some Abstractions

• Sorter something that knows how to sort
• Sortable something that can be sorted with an
  exchange-based sorted
• Container an array-like object with a size, a
  set, and a get.
• Comparer something that tells us which object is
  bigger.
• Each of these abstractions implies a vocabulary.
  We will (generally) extend this vocabulary to
  include name tags (descriptions) so we can see
  whos who.

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Sorter

• What does a sorter do?

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Sorter

• public interface Sorter
• public void sort(Sortable s)
• public String description()
• We could put the description in the toString
  too.

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Sortable

• Weve already done this one in the last project.
  Id like to add one more method String
  description(). This will allow us to debug a
  little more effectively.

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Sortable

• public interface Sortable
• public int size()
• public boolean gtr(int i, int j)
• public void swap(int i, int j)
• public void report()
• public String description()

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Container

• What does our container have to do?

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Container

• To make a good container, we need to use generic
  types so that well know whats inside.
• How do generic classes work???

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Indexable

• What methods are needed in Indexable?

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Indexable

• public interface IndexableltTgt
• public int size()
• public T get(int i)
• public void put(int i, T obj)

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Comparisons

• We dont know how to compare general types the
  user needs to tell us.
• How do we do that? An interface which carries a
  comparison function.
• As with the container, we need generics.

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Comparable

• public interface ComparableltTgt
• public boolean gtr(T x, T y)

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Project 3

• This one will be a bit harder!
• Start early! Ask questions! Get help!
• Lets Look