Introduction to the Lab Computer System and the Creation of a Simple Java Program

1
Introduction to the Lab Computer System and the
Creation of a Simple Java Program
CS 201 LAB Introduction to Object-Oriented
Programming Lab Session 1
Prepared by Robert Tairas
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Agenda

• Access to the lab machines
• Writing a Java program (Notepad Command Line)
• Create and edit a new Java class
• Compile and execute program
• Writing a Java program (Eclipse IDE)
• Create a new Java project
• Create and edit a new Java class
• Compile and execute program
• Identify and correct compile errors
• println() and print() methods
• Documentation

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Access to the lab machines

• Use your CIS student account
• If you dont have one, complete the form
  athttp//www.cis.uab.edu/it/accountApplication.ph
  p
• For today, use the generic user account

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Writing a Java Program

• Create and edit a new Java class using Notepad
• Compile and execute program using the Command
  Line (Prompt)

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Create and edit new Java program

• On the desktop, clickStart gtAll Programs gt
  Accessories gt Notepad

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Create and edit new Java program

• Another way to get to NotepadOn the desktop,
  click Start gt Run Type notepad and click OK

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Create and edit new Java program

• Write the following code to print Hello, World.
  to the standard output

public class HelloWorld public static void
main(String args) System.out.println("He
llo, World.")
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Create and edit new Java program

• From the menu in Notepad, select File gt Save As
• For File name, type c\temp\HelloWorld.java
• Click Save

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Compile and execute program

• On the desktop, clickStart gtAll Programs gt
  Accessories gt Command Prompt

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Compile and execute program

• Another way to get to Command PromptOn the
  desktop, click Start gt Run Type cmd and
  click OK

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Compile and execute program

• Type c and press Enter
• Type cd temp and press Enter
• Type javac HelloWorld.java and press Enter
• Type java HelloWord and press Enter

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Writing a Java Program

• Integrated Development Environment
• A tool that integrates editing, compiling,
  building, debugging, and other application
  development tasks.
• Can be downloaded at http//www.eclipse.org

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Open the Eclipse IDE

• On the desktop, clickStart gt All Programs gt
  eclipse

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Open the Eclipse IDE

• Select workspace where projects will be stored
• For Workspace, type C\temp\workspace

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Create a new Java project

• On the menu bar,chooseFile gt New gt Project

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Create a new Java project

• For Wizards,selectJava Project
• Click Next

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Create a new Java project

• For Project name,type Lab 1
• For Contents,select Createnew project
  inworkspace
• For JDK Compliance,select Use a
  projectspecific complianceand select 5.0
  fromthe dropdown options

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Create a new Java project

• (...continued fromprevious slide)
• For Project layout,select Use project folder as
  root for sources and class files
• Click Finish

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Create a new Java project

• You may be asked to switch to the Java
  perspective. If so, click Yes
• A perspective determines the initial layout of
  Eclipse, which includes the menu and tool bars
  and window views
• You can switch to different perspectives by
  selecting Window gt Open Perspective on the menu
  bar

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Create and edit a new Java class
menu bar
tool bar
OR
OR
right click on project
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Create and edit a new Java class

• For Name,type HelloWorld
• Make sure publicstatic void main(Strings
  args)is checked
• Click Finish

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Create and edit a new Java class

• Write a Java statement to print Hello, World.
  to the standard output

public class HelloWorld public static void
main(String args) System.out.println("Hello,
World.")
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Compile and execute program
menu bar
OR
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Compile and execute program
tool bar
OR
OR
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Compile and execute program
right click on the file
OR
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Compile and execute program

• Under Save Resources,click OK

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Compile and execute program

• The output message will be displayed in the
  Console window at the bottom

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Programming Style
public class HelloWorld public static void
main(String args) System.out.println("Hello,
World.")

• The Java language is case-sensitive
• For exampleHelloWorld is different from
  Helloworldmain is different from Main
  System.out.print is different from
  System.Out.print

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Programming Style
public class HelloWorld public static void
main(String args) System.out.println("Hello,
World.")

• Class names
• Required
• No spaces
• Should match file name, ie. HelloWorld.java
• Recommended
• Capitalize first letter

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Programming Style
public class HelloWorld public static void
main(String args) System.out.println("Hello,
World.")

• Method names
• Required
• No spaces
• Recommended
• Starts with a lowercase letter, e.g. getName()

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Programming Style

• Indentation
• Indent to indicate the nesting of code blocks
• User 2, 3, 4 spaces of indentation or tabs
• Be consistent

public class HelloWorld public static void
main(String args) System.out.println("Hello,
World.")
IDENTATION
IDENTATION
IDENTATION
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Identify and correct compile errors

• Edit the program and capitalize println
• Println will automatically be underlined in red
• The Problems window will display the error
• Indicators (circled above) will also display
  error

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println() and print() methods

• The only difference between println() and print()
  is that println() adds a newline at the end of
  its output

System.out.println("Hello, World.") System.out.pr
intln("Hello, World.")
OutputHello, World. Hello, World.
System.out.print("Hello, World.") System.out.prin
t("Hello, World.")
OutputHello, World.Hello, World.
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println() and print() methods

• Edit the code to display the output below

System.out.print("1700 ") System.out.print("Unive
rsity ") System.out.print("Boulevard
") System.out.print("Birmingham
") System.out.print("Alabama ") System.out.print
("35294 ") System.out.print("USA ")
Output1700 University Boulevard Birmingham
Alabama 35294 USA
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println() and print() methods

• How else could you do it?

Output1700 University Boulevard Birmingham
Alabama 35294 USA
System.out.println("1700 University
Boulevard") System.out.println("Birmingham
Alabama 35294") System.out.println("USA")
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Documentation

• Document your code using comments
• Block comments
• Single-Line comments
• End-Of-Line comments

/ Here is a block comment. /
/ Here is a single-line comment. /
System.out.print(Hello) // An end-of-line
comment.
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Documentation

• JavaDocs commentsJavaDocs
  examplehttp//java.sun.com/j2se/1.5.0/docs/api/j
  ava/lang/System.html

/ Returns an Image object that can then be
painted on the screen. The url argument must
specify an absolute _at_link URL. The name
argument is a specifier that is relative to the
url argument. ltpgt This method always
returns immediately, whether or not the image
exists. When this applet attempts to draw the
image on the screen, the data will be loaded.
The graphics primitives that draw the image
will incrementally paint on the screen.
_at_param url an absolute URL giving the base
location of the image _at_param name the
location of the image, relative to the url
argument _at_return the image at the
specified URL _at_see Image /