Neal Stublen

What's a class?  A class is comprised of a set of data and the actions taken on that data  Each action is represented by a method  A method is a set of statements that performs a specific task  Program execution will begin in a “main” method

What's an identifier?  An identifier is a name we give to a class or method  No whitespace - spaces, tabs, line breaks, etc.  Not a keyword - words reserved by the programming language  Most likely case-sensitive, so "count" is not the same as "Count"

Identifier "Casing"  UPPERCASE  lowercase  PascalCase or UpperCamelCase  lowerCamelCase  Each language typically has its own style for casing

Examples Pseudocode class Hello main() output "Hello” return endClass

Examples Java public class Hello { public static void main(String[] args) { System.out.println("Hello"); }

Examples C# public class Hello { static void Main() { System.Console.WriteLine("Hello"); }

What's a variable?  Data resides in the computer's memory  A variable names the data stored at a specific location in the computer's memory  Computer programs use variables to access and modify data stored in memory

What's a literal constant?  Data that doesn't change is a constant  Fixed values that appear in a computer program are called literals or literal constants

Examples input myNumber myAnswer = myNumber * 2 myAnswer = myAnswer + 42 output myAnswer  myNumber is a variable  myAnswer is a variable  2 is a literal constant  42 is a literal constant

Examples myName = "John Smith" output myName  myName is a variable  “John Smith” is a literal constant

Data Types  Numeric types Integer Floating point  String types  Casting converts between data types

Variable Declaration  Variables are declared with a data type  Variables are initialized with a value num myNumber num myNumber = 12 string myName string myName = "John"

Named Constants  Variables can refer to values that are fixed area = * radius * radius circumference = 2 * * radius

Named Constants  Variables can refer to values that are fixed num PI = area = PI* radius * radius circumference = 2 * PI* radius

Uninitialized Variables  Initialization places a known value into the memory location represented by a variable  Without initialization, the contents of a memory location could be anything  Typically called garbage And the source of many headaches

Assignment  Assign values to variables  Assign using a literal constant  Assign using another variable or expression  In some languages assignment can only be performed between matching types

Examples a = 1// ‘a’ now has the value ‘1’ b = a// ‘b’ now has the value ‘1’ c = a + b// ‘c’ now has the value ‘2’ num a = 1 string name = “John” name = a// Not allowed

Arithmetic Operations  Addition, +  Subtraction, -  Multiplication, *  Division, /  Modulus, %

Precedence  Multiplication and division precede addition and subtraction  Parentheses are evaluated from the inside out  * ( ( ) / )  * ( 9 / )  * ( )  * 4   14

Good Practices  Use code comments to clarify what is intended  Choose identifiers that are clear  Variable names are typically nouns (things, e.g. radius)  Method names typically combine a verb and noun (act on a thing, e.g. calculateArea)  Code that is easily readable can become self- documenting  What's clear now may not be clear later or clear to someone else

Searching for something?  a = w * l  area = width * length  aTmp = 98.6  avgTemp = 98.6  averageTemperature = 98.6  crntSpd  currentSpeed  ct  cnt  count

Readability  employeename  employeeName  employee_name  getTestComplete  isTestComplete

Spacing and Line Breaks  Use consistent spacing and line breaks  Indentation can show structure class Circle calculateArea apply area formula return endClass

Use Temporary Variables  Break complex algorithms down into component parts total = subtotal * (1 - discountRate) * (1 + taxRate) discount = subtotal * discountRate discountedTotal = subtotal - discount salesTax = dscountedTotal * taxRate total = discountedTotal + salesTax

Write Clear Prompts  Calculation error.  The starting balance is not valid.

Comment First, Code Second  Alternative to pseudocode and flowcharting  Stub out a class or method  Write comments to document what should happen within a method  “Rewrite” the comments as code

Example fillContactList() { // Retrieve contacts from a database // Sort contacts by last name // Add each contact to the contact list }

Programming Structures  Sequence structure Performs a series of actions in order  Selection structure Performs one action or sequence or another action or sequence based on a decision  Loop structure Repeats an action or sequence

Review  What is the value of: 8 – 4 * 6 / 4 ( 8 – 4 ) * 6 / 4 8 – 4 * ( 6 / 4 )

Exercise  Case Projects, p. 61, #1

Summary  Classes  Identifiers  Variables  Data types  Arithmetic operations and precedence  Good practices  Programming structures