Read for next week: 4.1-4.9
Fri 9/17 6:00 PM CodeWarrior Tutorial o Questions?
Fri 9/17 6:00 PM Assignment 0 o UML Diagrams

Differentiating class and instance stuff in the class: underline class stuff (opposite of object diagram name)

Representing methods in the class

Arguments

Return values o Questions?
Mon 9/20 11:58 PM CodeLab #2 o Questions?
Fri 9/24 11:58 PM CodeLab #3 o Should be able to do some; will cover next week:

Infer class declaration from sample programs and CodeWarrior

Declaring constants

Standard input o Distinction between “expression” and “statement” o Questions?
What are the five stages of the software life cycle? o Analysis, Design, Coding, Testing, Operation
When does debugging occur? o Testing and (unfortunately) Operation
1 CS 302 Lecture 6 0917

Reference (object) and primitive (numerical) data types
Steps to use an object (how different from primitives?) o Declare o Create o Send messages
Declaration o Memory diagram: primitive versus reference
Creation o Declaration does not create object o May use same identifier to refer to different instances of the same class at different times o Memory diagram: primitive versus reference

Distinction clear?

Note that both always use same size for variable itself, but that the amount of memory used by the object can vary widely (even among objects of the same class; e.g. lists: different people’s favorite numbers) o Assigning one object variable to another

Does not create new object

Means having two names for the same thing

Sharing
2 CS 302 Lecture 6 0917

Message sending o Can only do after the object has been created o Calling a method

Message usually refers externally

Method usually refers internally
What types are arguments to setSize and setTitle? o New type for setVisible: boolean o setSize refers to pixels
3 CS 302 Lecture 6 0917

Three parts to all Java programs
Comments o Computer ignores o Not necessary for execution o Documentation

Help programmers understand program
 State purpose of program
 ID/explain/summarize code blocks

Note modifications o Disable sections of code during testing
Comment marker: example code
Single-line comment o Extends from marker to end of line o Example
Javadoc comments: later
Header comment: examples o CodeWarrior Tutorial o Example program
Import: use pre-defined classes whenever possible
Packages: Java comes with many
Package hierarchy o Subpackages o Multiple dots
Import statement o Avoids use of fully qualified name o Allows use of class name by itself o Does not copy classes into your program
Star o Import all classes in a package o Conventional, but can input by name specifically
4 CS 302 Lecture 6 0917

5
Class declaration o “Class” reserved word o Example o Class members

Data values

Methods

Examples o Main class

Every program must include at least one

In CodeWarrior, designate by giving it the same name as the file

Example o Refer to whole application as “<main class> application”; Example
Method declaration o Example o Modifiers
 State which kind of method

Many o Return type states the type of the data value that the method returns
CS 302 Lecture 6 0917

Completely different programs can be created readily by using different objects
6 CS 302 Lecture 6 0917

Steps to execute program
Require more specifics to actually do in particular development tool
Use <main class name>.java for file name
Compilation o May need to place source in project and compile that o Bytecode file: file containing bytecode o Compilation errors easiest type to correct
Execution o Bytecode is system independent o Occurs on interpreter

System independent

Java Virtual Machine (JVM)

Must have specialized for each system o Errors detected by interpreter
7 CS 302 Lecture 6 0917

Right now, learn to use some existing classes
Later, learn to define own
Java API o Application programming interface o Documentation for the standard classes
JoptionPane for output o Display computed result to user o Window types (in GUI environment)

General purpose frame, e.g. JFrame

Special purpose dialog

JDialog

Method showMessageDialog o First argument

Controlling frame object

Dialog positioned at center of this, or, if no arg, of screen o Creates instance of JDialog internally o Class method
 Don’t need to create object to use it

Just use <class name>.<class method> o Example: display “What’s\nup?” in JFrame jf2
8 CS 302 Lecture 6 0917

9
String o Explicit use of new optional; draw mem diagram o Substring

First argument

Beginning position

Count from 0

Is displayed

Second argument

End position

Is not displayed

Creates new string

Original string left intact

Generates error if given illogical arguments

Examples
 “together” o 0-2= “to” o 2-5= “get” o 5-8= “her”
 “michelle”: 3-7= “hell”

You think of one o Length

Return # of characters in a String

Examples o IndexOf
 Locate index position of substring within another string

Returns position of first char of substring
 Returns -1 if substring not found

Case-sensitive

Returns first occurrence if multiple exists
CS 302 Lecture 6 0917

Date o Time instance o Millisecond precision o Automatically set to time created (from OS) o toString method converts to human-readable: Sat
Apr 20 15:05:18 PDT 2002 o internally represented as time since epoch (Jan 1,
1970 00:00:00 GMT) o Use GregorianCalendar for real dates
SimpleDateFormat o Change display format of Date o Pass formatiting string when create instance of
SimpleDateFormat o Formatting string case-sensitive
SimpleDateFormat simpleDF; simpleDF = new SimpleDateFormat(“…”);
System.out.println(simpleDF.format(new
Date()));
10 CS 302 Lecture 6 0917

JoptionPane for input o showInputDialog method o Access input by assigning return result to String variable o Returns null if cancel clicked o Returns empty string if nothing entered & OK clicked
Get into the habit of developing according to the software life cycle stages (even though not strictly necessary for small programs)
Map out overall plan o ID classes necessary o ID implementation steps to follow o Outline program logic o Write design document
Consider design alternative o Better depends on metric o Always developing for users
CodeLab #2 Due
More Chapter 2
If finish, review Chapter 3 so far
11 CS 302 Lecture 6 0917