Chapter 1: Java Fundamentals 1 (c) Gary R. Smith, MS.

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JAVA: A BEGINNER’S GUIDEChapter 1: Java Fundamentals

(c) Gary R. Smith, MS.

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KEY SKILLS AND CONCEPTS

Know the history and philosophy of Java

Understand Java’s contribution to the Internet

Understand the importance of bytecode Know the Java buzzwords Understand the foundational principles

of object-oriented programming Create, compile, and run a simple Java

program(c) Gary R. Smith, MS.

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KEY SKILLS AND CONCEPTS

Use the if and for control statements Create blocks of code Understand how statements are

positioned, indented, and terminated Know the Java keywords Understand Java identifiers

(c) Gary R. Smith, MS.

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THE ORIGINS OF JAVA

Conceived by James Gosling, Patrick Naughton, Chris Warth, Ed Frank and Mike Sheridan at Sun Microsystems in 1991.

Originally designed as a platform-independent language to control embedded consumer electronic devices.

Based on C and C++ languages. The advent of the Internet promoted the

change from consumer electronics to the Internet programming.

(c) Gary R. Smith, MS.

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HOW JAVA RELATES TO C, C++, AND C# Java’s syntax is inherited from C. Java’s object model is adapted from C++. Java was developed by programmers for

programmers. Java is not upwardly or downwardly compatible

with C++. Designed to solve a different set of problems. C#’s syntax and structure are similar to Java. C# was designed for a different computing

platform.

(c) Gary R. Smith, MS.

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JAVA’S CONTRIBUTION TO THE INTERNET Java Applets – special type of program

that gets automatically executed by a Web browser. Intended to be small programs. Is downloaded upon demand. Use to display data, handle input, and

provide simple functions. Executes locally rather than on a server.

(c) Gary R. Smith, MS.

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JAVA’S CONTRIBUTION TO THE INTERNET Security – Applets are confined to the

Java execution environment. Cannot access other parts of the computer. Reduces the likelihood of malicious code or

breaches of security.

(c) Gary R. Smith, MS.

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JAVA’S CONTRIBUTION TO THE INTERNET Portability

Java can run on a variety of different platforms using the same code called Bytecode.

Bytecode Not executable code. Is interpreted by the Java Virtual Machine

run-time environment. Highly optimized for the interpretive

process.(c) Gary R. Smith, MS.

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JAVA BUZZWORDSSimple Has a concise, cohesive set of features that makes it easy to

learn and use.

Secure Provides a secure means of creating Internet applications.

Portable Programs can execute in any environment for which there is a Java run-time system.

Object-oriented Embodies the modern, object-oriented programming philosophy.

Robust Encourages error-free programming by being strictly typed and performing run-time checks.

Multithreaded Provides integrated support for multithreaded programming.

Architecture-neutral

Is not tied to a specific machine or operating system architecture.

Interpreted Supports cross-platform code through the use of Java bytecode.

High performance

Bytecode is highly optimized for speed of execution.

Distributed Designed with the distributed environment of the Internet.

Dynamic Programs carry with them substantial amounts of run-time type information that is used to verify and resolved accesses of objects at run time.

(c) Gary R. Smith, MS.

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OBJECT-ORIENTED PROGRAMMING

Object-Oriented Programming is a programming model that focuses on data and the code that manipulates that data.

Key Features: Encapsulation – programming mechanism that

binds together code and the data it manipulates. Polymorphism – programming mechanism that

allows a single interface to have many forms. Inheritance – the process by which one object

can acquire the properties of another object.

(c) Gary R. Smith, MS.

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OBJECT-ORIENTED PROGRAMMING

Class – Java’s basic unit of encapsulation. Often referred to as a program. May contain both data members (aka instance

fields or instance variables) and code members (aka methods).

A class is the blueprint to construct an object. A class is not the object. Objects are instances of a class.

Data and methods can be private (known only within the class) or public (known to other classes).

(c) Gary R. Smith, MS.

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ANATOMY OF A JAVA CLASS

// Program: AJavaProgram.java Inline comment

// Author: Gary R. Smith Inline comment

// Date Written: 8/16/2014 Inline comment

/* This program displays a message Block comment (multi-line) on the monitor */

(/* begins comment, */ ends comment)public class AJavaProgram

Class header (name of the class){

Starts a block of code (class)// This is where the program starts and ends. Inline commentpublic static void main(String args[]) Method header{

Starts a block of code (method)// Displays a message on the monitor

Inline commentSystem.out.println(“Java is fun!”);

Executable statement}

Ends a block of code (method)}

Ends a block of code (class)

(c) Gary R. Smith, MS.

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PROGRAM ELEMENTS

// (two slashes) indicates an inline comment. Not compiled as part of the program Provides in-program documentation Comment goes to the end of the line

/* and */ indicates a block comment Everything between /* and */ are comments Not compiled as part of the program Can be as long as you want.

Don’t be stingy on comments!

(c) Gary R. Smith, MS.

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PROGRAM ELEMENTS

Class header (public class AJavaProgram) defines the name of the program. Public is an access modifier that defines

whether or not outside classes can access the class.

Must be the same name as the file name public class AJavaProgram must have a file

name of AJavaProgram.java

(c) Gary R. Smith, MS.

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PROGRAM ELEMENTS

Curly braces: { } Denotes a block of code treated as a unit. Encapsulates classes Encapsulates methods Encapsulates program elements

supporting multiple statements.

(c) Gary R. Smith, MS.

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PROGRAM ELEMENTS

Method header (public static void main(String args[]) defines a named block of code. Public is an access modifier. Static means the method belongs to the class itself

and not an instance of the class. Void (return type) means the method does not return

any value. main() is the name of the method which must include

the parenthesis, which hold parameters. String args[] is the parameter of the main() method.

Methods may have zero or any number of parameters. String args[] is a parameter of the main() method.

(c) Gary R. Smith, MS.

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PROGRAM ELEMENTS

System.out.println(“Java is fun!”); is an executable statement. System is a predefined class out is an object of the System class println() is a method of the System.out

object “Java is fun!” is a parameter that is passed

to the println() method. Note it is String data.

The semicolon ‘;’ terminates an executable statement.(c) Gary R. Smith, MS.

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SYNTAX ERRORS

Syntax errors: violations of the language rules. Caught by the compiler Incorrect punctuation Misspelled keywords and identifiers Not specifying balanced (open and/or

closing) parenthesis, curly braces, or square brackets.

(c) Gary R. Smith, MS.

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DATA TYPES

Data types define: How data is stored in memory The minimum and maximum values a data item can

hold The amount of memory allocated for the data item.

Each data type is based on a class. Java primitive data types are:

Integer types: byte, short, int, long Floating point types: float, double Boolean type: boolean Character type: char

(c) Gary R. Smith, MS.

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SOME IMPORTANT DEFINITIONS

Field - An area of a database record, graphical user interface form, data item, or memory into which a particular item of data is stored. Can be subdivided into two general

categories: Variables: Those data items which can be

programmatically changed. Constants: Those data items which cannot be

programmatically changed.

A field is associated with a data type.(c) Gary R. Smith, MS.

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JAVA KEYWORDS

abstract assert boolean break byte case

catch char class const continue default

do double else enum extends final

finally float for goto if implements

import instanceof

int interface long native

new package private protected public return

short static strictfp super switch synchronized

this throw throws transient try void

volatile while * true * false * null

Keywords have special meaning to the Java compiler. These keywords cannotbe used as names for variables, classes, or methods.

* Although not keywords, true, false and null are also reserved words.

(c) Gary R. Smith, MS.

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IDENTIFIERS IN JAVA

Identifiers are names given to classes, objects, methods, variables, and other user-defined items. Can start with any letter, the underscore

character, or dollar sign. May contain (after the first character)

letters, numbers, the underscore character, or dollar sign

Cannot have any embedded spaces. Are case sensitive.

(c) Gary R. Smith, MS.

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IDENTIFIERS IN JAVA

Class identifiers Begin each word with an upper case letter. All other letter are lower case. Example: AJavaProgram, Employee

Variable/object/method identifiers Begin the first word with a lower case letter. All other words begin with an upper case letter. Use camel casing/Hungarian notation. Example: employeeNumber, calculateInvoiceTotal

Note: This is a convention, not a language requirement.

(c) Gary R. Smith, MS.

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JAVA CLASS LIBRARIES

Java contains hundreds of predefined classes stored in libraries.

System is a class library automatically included in every Java program.

You can create your own class libraries.

(c) Gary R. Smith, MS.

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THE JAVA PROGRAMMING ENVIRONMENT

(c) Gary R. Smith, MS.

Java source programs end with a .java extension.Compiled Java programs end with a .class extension.

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PROGRAM DEVELOPMENT CYCLE

(c) Gary R. Smith, MS.

Analyze the requiremen

ts

Develop an algorithm

Code the program

Test the program

Implement the

program

Maintain the

program

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PROGRAM DEVELOPMENT CYCLE

Analyze the requirements What is the expected result? What data is needed to yield the expected

result? What actions are to take place What output, if any, is to be produced? Clarify calculations with the user. What are the objects?

(c) Gary R. Smith, MS.

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PROGRAM DEVELOPMENT CYCLE

Develop an algorithm (solution to the problem) Pseudocode Flowchart IPO (Input/Process/Output) Diagram Decision Trees Truth Tables Object Dictionaries Develop testing criteria

(c) Gary R. Smith, MS.

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PROGRAM DEVELOPMENT CYCLE

Code the program What standards does the organization

have? Naming conventions Program structure Libraries Internal documentation

(c) Gary R. Smith, MS.

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PROGRAM DEVELOPMENT CYCLE

Test the program Unit tests - testing a single method Program tests – testing the operation of

the program System tests – testing to insure all

programs work properly together Acceptance tests – testing by the user to

verify everything works as specified.

(c) Gary R. Smith, MS.

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PROGRAM DEVELOPMENT CYCLE

Implement the program File/data conversion User/system documentation Performance tuning

Types of implementations Phased Pilot Parallel Direct cut over

(c) Gary R. Smith, MS.

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PROGRAM DEVELOPMENT CYCLE

Maintain the program Changes to programs are inevitable.

Governmental regulations Changes in business practices Technological changes Acquisitions and mergers

Follows the first 5 steps of the program development cycle.

(c) Gary R. Smith, MS.

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NEED MORE HELP?

Tutorials: http://

docs.oracle.com/javase/tutorial/index.html Java™ Platform, Standard Edition 8 API

Specification http://

docs.oracle.com/javase/8/docs/api/index.html

(c) Gary R. Smith, MS.