Jan 6, 2020 -- Notes

IT 313 -- Jan 6, 2020

Is IT 313 the Right Course for You?

IT 313 is a third programming course.
The official prereqs for IT 313 are IT 211 and IT 212.
However, if you have taken a different two quarter programming sequence in a high level language such as Ruby, Python, C#, or C++ you are qualified to take IT 313.
You are underqualified for IT 313 if you have only taken one high level programming course.
You are overqualified for IT 313 if you have taken a data structures course in Java, such as CSC 300.
The textbook for this class, Big Java, Late Objects by Cay Horstmann, is required.
Use the optional textbook if you are interested in the details of software design patterns:
Head First Design Patterns by Freeman and Freeman, O'Reilly, 2004.

Course Website

Announcements Lecture Notes Documents Projects Exam Info Prof Info Syllabus

Review Quiz

What are these datatypes?
integer floating point character string boolean
Ans: Here is a table showing the Python and Java primitive datatypes. The numbers in parentheses are the number of bytes needed to represent that datatype in the Java Virtual Machine.

Meaning	Python	Java
Integer	int (unlimited)	byte (1) short (2) int (4) long (8)
Floating Point	float (8)	float (4) double (8)
Character		char (2)
Character String	str (4 or 8 byte reference variable)	String (4 or 8 byte reference variable)
Logical	bool (1)	boolean (1)

An integer value is a whole number: positive, negative, or zero. For example: 834564, -5348372, or 0.
By default, Java int variables are between -2 billion and 2 billion.
A floating point value is a number with a decimal point and optional exponent. E.g.: 5.342, -6.3372, 0.0, 3.4356e11 (means 3.456 × 10¹¹).
A character constant is a single unicode character. E.g.: 'W', '5', '$'. We will see how to represent non-keyboard unicode characters later.
Strictly speaking, Java can only deal with 2-byte Unicode characters. Chinese has so many characters, that 4 bytes are needed to represent all of them.
Java character constants always use single quotes.
A string constant is a sequence of zero or more characters: "dog", "elephant", "12345", "!@#$%^&*()", "" (empty string).
A boolean constant is either true or false.

List the Python operators that you know. Most of these also work as Java operators. Ans:

Arithmetic: +  -  *  /  %

String Concatenation: +

Comparison: <  >  <=  >=  ==  !=

Logical: &&  ||  ^  !

Bitwise: &  |  ^  ~

Assignment: ++  --  +=  -=  *=  
            /=  %=  &=  |=  ^=  

Array Lookup:  [ ]

Grouping, Function Invocation:  ( )

Tertiary Conditional Operator:  ?

Member Access:  .

The ? operator is also called the Elvis operator, because it looks like Elvis Presley's hair when turned sideways.
See Horstman, page 866 for an operator precedence table.

Name some common control structures. Ans:
Python: if..else, if..elif..else, while, for.
Java: if..else, if..else if..else, switch, while, do..while, for.
Give some plausable examples of objects in the sense of object oriented programming. Ans:
```
Person  Student  Pet  BasketballPlayer  Transaction  CatalogItem  Automobile
```

Working with Java

Understand three components to effectively use Java:
1. Object oriented programming (OOP),
2. A modern editor such as IntelliJ,
3. The application programming interfaces (API) in the Java Class Library

The HelloWorld Example

Look at the HelloWorld Example project.
What do you notice about a Java program that is different than Python or other languages that you know?
Compile and run this program with the Java command line programs javac and java:
Install Java 11 and IntelliJ IDEA on your computer. See the Announcements Page for links.
Important: install version 11 on your machine to be compatible with the version of Java in the classroom and in the labs.

Standard IO

Standard IO means reading from the keyboard and writing to the computer screen in a Command Prompt Window (Windows) or Terminal Window (Unix or Linux, e.g., on a Mac).
The keyboard and computer screen together are called the console.

Here is a summary of the three standard IO streams:

Index	Name	Java Object	Physical Device	IntelliJ Color in Output Window	Redirection Symbol
0	stdin	System.in	Keyboard	Green	<
1	stdout	System.out	Screen	Black	>
2	stderr	System.err	Screen^*	Red	2>

^*But not redirected even if Standard Out is redirected.

Redirection

Examples of Java IO redirection in a Command Window. The DOS or Unix prompt is >.

Redirect Standard Out:

> java Greeter1 > greeting.txt
Enter your name: Steve
> type greeting.txt
Hello, Steve, how are you?

Redirect Standard Out and Standard Err:

> java Greeter1 > greeting.txt 2> prompt.txt
Steve
> type greeting.txt
Hello, Steve, how are you?
> type prompt.txt
Enter your name:

Redirect Standard Out, Standard Err, and Standard In:

> type name.txt
Steve
> java Greeter1 < name.txt > greeting.txt 2> prompt.txt
> type greeting.txt
Hello, Steve, how are you?
> type prompt.txt
Enter your name:

Redirect Standard Err to same file as Standard Out:

> java Greeter1 > greeting.txt 2>&1
Steve
> type greeting.txt
Enter your name: Hello, Steve, how are you?

2>&1

Eclipse does not directly support IO redirection. Read from or write to files directly instead.

Some Windows and Unix Shell Commands

IntelliJ Editor

We are using the IntelliJ Editor for this course. The Java projects that you submit must be IntelliJ projects.
IntelliJ is considered to be a more modern editor than Eclipse.
Here are two documents that show how to create simple IntelliJ projects:
- Creating a HelloWorld Project See the HelloWorld Project
- Creating a Project with Multiple Modules See the Greeter Project
IntelliJ has many key-combination shortcuts that allow experienced Java programmers to write Java source code very quickly. You don't need to learn all these shortcuts for this class. However, there are two shortcuts that you will probably want to start using immediately:
- Control-S: Save all.
- Alt-Enter: Show intention actions and quick fixes.
Here are other shortcuts on this IntelliJ Default Keymap page if you are interested.

Project 1

Look at Project 1.