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Unit 3 - Implementing ("Creating") Classes

   Powerpoint - Chapter 3

   Implementing ("Defining") Methods

What we need to know to begin writing our own methods

   Class Constructors

A constructor is a special method that we call to create an object and initialize its instance variables. Unlike all other methods, a constructor is called when the new operator is executed

   Parameters and Arguments

When a method is called, the parameters in the method heading receive the values of the corresponding arguments in the method call. This is how information is passed into a method

   Instance Variables, Parameter Variables, and Local Variables

The scope, lifetime, and initial value of a variable depends on how the variable is used (i.e, where it is declared)

   BankAccount.java

The BankAccount class provides examples of everything we need to know to create a class - instance variable declarations, a class constructor, accessor and mutator methods, and parameter variables and local variables
BankAccountTest.java - test class for the BankAccount class

   Assignment #3 - Creating a Class

   Algorithms, Pseudocode, and Stepwise Refinement

Where methods come from

   Shadowing

If a method has a parameter variable or local variable with the same name as an instance variable, then the instance variable is "shadowed" or "hidden" by the parameter or local variable and can not be accessed in that method. We must use this to guard against shadowing

   Method Overloading

Overloading class constructors enables us to create objects with varying numbers of "construction parameters" passed
BankAccount2.java (Same BankAccount class, but with overloaded constructors)
OverloadedConstructors.java (Test class for BankAccount2 class)

Unit 4 - Fundamental Data Types, Reading User Input, and More

   Powerpoint - Chapter 4

   Java's "Primitive" Types

The so-called "primitive" types are the exception to the "Everything in Java is an Object" rule, as they are implemented differently. Although 6 different numeric types are available, there is generally no reason to use any other than int and double

   Java Arithmetic

The arithmetic operators, operator precedence, and integer division and modulus ("mod")

    PizzaCalculatorTest.java

Shows arithmetic expressions and assignment statements

   Mixed-Type Expressions

When an arithmetic operation involves operands of two different types, the result is "promoted" to the higher type...

   Type Conversions (aka: Type "Casting")

"Narrowing" vs. "Widening" type conversions and implicit and explicit type conversions explained. Also, how to use an explicit type cast to avoid integer division

   Math Class Methods

A table summarizing some of the more useful methods of Java's Math class

   PythagorasTest.java

Shows how to call the static Math class methods, using sqrt and pow

   Using the showInputDialog method of the JOptionPane Class

How to create a dialog boxes for interactive input

   InputDemo.java

Demonstrates interactive input using JOptionPane, and the parseInt(), and parseDouble() methods

   Assignment #4 - Integer Arithmetic, Arithmetic Expressions, and Reading User Input

   Defined Constants

Using defined (aka: "symbolic") constants helps make our programs easier to understand and modify

   Formatted Output - the printf Method

How to use printf to control the width of the output field, number of decimal places shown, right or left justification, etc

   Implicit and Explicit Method Parameters and this

"Explicit" parameters are those that appear in the parameter list in the method declaration. In addition, every non-static method is automatically passed one "implicit" parameter, which is a pointer to the object for which the method was called. It's name is this

   BankAccountTest2.java

Demonstrates objects passed implicitly and explicitly, this, and calling a method of a class from another method of the same class

   The "Shortcut (or, "Arithmetic") Assignment Operators

By combining an arithmetic operator ( * , / , % , + , - ) with an assignment, these operators save you a few keystrokes

   The Autoincrement and Autodecrement Operators

Because incrementing and decrementing counters are such common operations, Java has a set of operators that do just that (and save you a few keystrokes)

Unit 5 - Decision-Making (aka: "Selection" or "Conditional Execution")

   Powerpoint - Chapter 5 (Decisions)

   Relational Operators and Expressions

A relational expression compares two quantities for one of 6 possible relationships

   The if Statement

Syntax and execution of the single-alternative and two-alternative forms of the if statement

   PayMaster1.java

Demonstrates the single-alternative if statement

   PayMaster2.java

The two-alternative if statement

   "Nested" if Statements and "Cascaded" ifs

A "nested if" is an if statement within an if statement. In the "if" branch, this creates more complex conditions; in the "else" branch, multiple alternatives. A better way to code multiple alternatives is via "cascaded ifs"

   Testing Strings for Equality

To test Strings for equality we cannot use the "==" operator. Instead, we call the equals() and equalsIgnoreCase() methods

   Assignment #5 - Intro to Decision-Making

   Boolean Operators and Expressions

Boolean operators !, &&, and ||, operator precedence, truth tables, and DeMorgan's Laws

   Primitive Type boolean

Boolean literals, variables, assignments, and methods

   LeapYearTester2.java

Demonstrates all things boolean: operators, expressions, variables, assignment statements, and a boolean method

   Assignment #6

Advanced Decision-Making: Boolean Operators, Expressions, and Methods

   Testing Floating-Point Numbers for Equality

Because floating-point arithmetic is only approximate, testing floating-point numbers for equality is not dependable. Instead, we test whether the difference between two numbers is "close enough" to zero that we can consider them to be "equal"

   More on Decision-Making

"Shortcut" (or, "lazy") evaluation of boolean expressions, tesing programs that make decisions, impossible conditions and unavoidable conditions, and the "dangling else" problem (and how to avoid it)

   The switch Statement (Optional)

When testing an int, String, or char expression for equality to any of a list of constants, the switch statement requires a bit less coding than cascaded "if" statements

   SwitchDemo.java

Shows two switch statements - one with break statements and one with the default "fall through" behavior

Unit 6 - Style and Documentation Standards for Java Programs

   Programming Style

Conventions for creating programs that are easy to read

   Java "Documentation Comments"

When a class contains special Java "documentation comments" the javadoc utility program can create HTML "help" pages that contain everything a programmer needs to know in order to use it: the purpose of the class, how to create objects, what methods are available, and how to call them

   Using the javadoc Utility in NetBeans

How to use the javadoc utility to automatically generate HTML "help" pages for your classes. These pages will have the same format as the official Java API Language Documentation

   Packages

A package is a folder for storing related classes. In NetBeans, the "default" package is the src folder. Here is how to create and use your own packages and how to get NetBeans to do it all for you!

   Internal Documentation

Internal documentation consists of comments - included in your Java code - that explain what you are doing and how you are doing it. This is a necessity in the real world where programmers may be called upon to debug or modify code written by others

Unit 7 - Iteration (aka: "Repetition" or "Looping")

   Powerpoint - Chapter 6 (Looping)

   The while Statement

Syntax and execution of Java's while loop. Loop control variables and loop "necessities"

   DataSet.java | DataSetTester.java

The DataSet class computes the average and maximum of a set of data values, using a counter and an accumulator. The DataSetTester class uses a while loop to read and process any number of data values until end-of-file

   InvestmentTester.java

CH's Investment class demonstrates a while loop and a for loop

   The for Statement

Java's for loop is a count-controlled while loop, used when you can determine in advance the exact number of iterations to be done

   GaussTester.java

Gauss class uses a for statement to compute sum of integers from 1 to n, where the user enters n

   TemperatureConverter.java

Uses a for statement to print a table of Fahrenheit temperatures and their Celsius equivalents

   Assignment #7 - Repetition and Decision-Making

Date.java | SpeedDating.java | Date.html

   The do-while Statement

The "do-while" loop is a post-test loop, meaning the loop body is always done at least one time (unlike the for and while loops). Also, when to use each type of loop

   PasswordTester.java

The Password class creates a password and gives the user 3 attempts to match it. Shows a do-while loop with a compound condition and loop postconditions

   Nested Loops

The inner loop is fully executed - from the initialization of the loop control variable until the boolean expression becomes false - on each iteration of the outer

   TableTester.java

Uses nested for statements to print multiplication tables

   Intro to the Scanner class

The Scanner class can be used to extract the individual "tokens" from a string

   InputDemo2.java

Uses Scanner methods next(), nextInt(), and nextDouble() to extract tokens from a string. This allows us to enter multiple input values - separated by spaces - in showInputDialog()

   ScannerDemo.java

Nested while loops. The outer loop uses Scanner method hasNext() to read any number of lines of text, until end-of-file. The inner loop then uses Scanner methods hasNext() and next() to extract each "token" from the line read

   The "Loop and a Half" Problem and the break Statement

The break statement causes an immediate exit from the loop that contains it

   More on Iteration

Loop pitfalls and implementing the repeat-until construct in Java

   Random Numbers

Java's Random class makes it easy to generate random numbers - floating-point numbers, ints, and ints within a specified range