CIS110203 Intro to Computer Science Lab

1
CIS110-203Intro to Computer Science Lab 9

• TA Catherine Stocker
• Mentor Jay Fiddelman
• University of Pennsylvania
• 1 November 2007

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Todays Agenda

• Sit in your pair programming groups!
• General Stuff
• Arrays
• Lab Work

3
Monitors

• Turn em off

4
General Stuff

• How was the test?
• If you feel like youre falling behind, please
  come talk to me. Also
• Go to office hours (mine are Weds 2-4).
• Go to the free tutoring.
• You can even email me privately and ask me to
  cover something you didnt understand from class.
• Whatever you do, dont cheat!
• What can I do in lab to help?

5
Arrays

• Ways to create
• String s
• s spot on stack is null
• String s new String4
• OR
• String s
• s new String4
• s spot on stack holds memory address. Heap
  allocates 4 spots, each big enough to hold a
  String.
• String s hi, hello, hey, howdy
• OR
• String s new String hi, hello,
  hey, howdy
• OR
• String s
• s new String hi, hello, hey,
  howdy
• s spot on stack holds memory address. Heap
  allocates 4 spots, each big enough to hold a
  String. hi is in spot 0, hello in spot 1,
  hey in spot 2, howdy in spot 3

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Arrays

• Ways to NOT create
• String4 s
• String s new String
• String s
• s String4
• String s new Stringhi, hello, hey,
  howdy
• String s
• s hi, hello, hey, howdy
• String s
• s new String4hi, hello, hey,
  howdy
• Lots more

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Arrays

• Some things to understand
• Very useful, compact way to handle a lot of
  variables
• Even better if you want to do the same thing to
  all of them.
• Arrays are homogeneous
  
• All data stored in them must be of the same type
• Arrays are indexed 0 to length-1
• Dont forget to use for(int i0 ilta.length i)
  or you will get an Index out of Bounds exception
• Indexes can be any int expression
• 5, c (int variable), c2, x.getVal() (if getVal
  returns an int), etc
• Can get passed to and from methods
• public int arrayMethod(double a)
• Arrays are reference types (i.e. like objects, a
  memory address is stored on stack), so does
  what

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Lab Work

• Break into the same groups, different pairs
• Arrays of Primitives http//www.seas.upenn.edu/c
  se1xx/projects/Arrays/ArraysOfPrimitives/
• Array of Objects
• http//www.seas.upenn.edu/cse1xx/projects/Arrays
  /ArrayOfObjects/
• Submit both.
• Ok to finish on own or with partner.
• Each person submits code.
• Comments on top should cite all authors.

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Later

• Come talk to me if you need help!