Chapter 1: Introduction

Version 3.1¹

Tuesday

Handouts:

• Hello.java
• HelloObj.java

Plan:

1. Announcements:
2. Syllabus
3. Chapter 1: Networks, Java, Program Development, Objects
4. Lab: Lab 1
   • Unix (Linux) review if needed
   • Java program

(1.1–1.2) Computer Processing, Hardware Components

You should know these topics already. Read these sections to be sure.

(1.3) Networks

• Network Connections

  • Network addresses
  • Packets

• LAN and WAN

  • LAN = local area network
  • WAN = wide area network

• The Internet

  • A network of networks
  • Origins
  • Protocols

  • TCP/IP

    • IP address

    • Domain Name System (DNS)

      • Host and domain names
      • Translation to/from IP addresses

• The World Wide Web

  • Hypertext
  • HTML: HyperText Markup Language
  • Browsers and servers
  • HTTP: HyperText Transfer Protocol
  • URLs

(1.4) The Java Programming Language

• Listing 1.1: Lincoln.java

  • Compiling
  • Running

  • Comments, 3 kinds:

    /* multi-line C-style comment */
    /** multi-line Javadoc comment */
    // single-line C++-style comment to end of line
    

• Figure 1.18 list of reserved words—you'll become acquainted with most of these gradually, so don't try to memorize it.

• Style guidelines: pp. 33–35

  • Bad style: Listings 1.2, 1.3

(1.5) Program Development

• Levels of language

  • High-level language, assembly language, machine language
  • Compilers and interpreters

  • Compilers and interpreters for Java:

    • Normally "compiled" to "Java bytecode", machine language for the Java Virtual Machine (JVM), which is not (usually) a hardware processor but an imaginary ("virtual") processor implemented in software (the Java interpreter)
    • The Sun Java interpreter interprets JVM machine instructions, but includes a "just-in-time compiler" which notices when parts of the program are executed repeatedly and speeds them up by compiling all the way to native machine language.
    • Then there's the GNU compiler for Java (gcj), which is an "ahead-of-time compiler" that can compile to native machine language up front, or can compile to Java bytecode (which can be interpreted by gij, the GNU interpreter for Java, or by any Java interpreter).

• Syntax and semantics

• Three kinds of errors:

  • compile time
  • run time
  • logic error

• What do error messages look like in Java?

• Using Emacs to go to the next error message and corresponding line of code (other IDEs may have similar features).

(1.6) Object-Oriented Programming (OOP)

• Review: objects are bundles of …

  • Data ("fields", "attributes", "instance variables")
  • Functions ("methods")

• Inheritance: Subclasses derive data and functions from superclasses.

• Encapsulation, Polymorphism: Just mention the terms, defer details.

OOP in Java

• Java is an OOP language
• But not every Java program uses OOP seriously
• Two versions of "hello world":
  • Hello.java
  • HelloObj.java

Exercises

pp. 53–55: EX 1.15–1.18, 1.20

Programs

pp. 55–56: PP 1.2 (deliberate errors) in class

Lab

• Assignment

  • Select one program from PP 1.3, 1.4, 1.7, 1.8 (see lab instructions for details)

  • Linux tutorial, parts 1–4 (catch up in case you didn't do these last semester)