Download Notes - Tom Kleen

Day #1.
Getting Java for your personal computer
Go to http://www.oracle.com/technetwork/java/javase/downloads/jdk-netbeans-jsp142931.html. Accept the license agreement and then download the software.
Run the setup program. It should install two things on your computer:
1. The Java Development Kit (JDK). This is Java.
2. The NetBeans Integrated Development Environment (IDE). This is your editor and
compiler.
Creating a New Java Application
1. Create a folder called Java on your M drive for storing all of your programs this
semester.
2. Start NetBeans.
3. Choose File | New Project. Under Categories, select Java. Under Projects, select Java
Application and click Next.
4. Under Project Name, enter the name of your app. Make sure the Project Location is
set to your M drive (\\Host3\Students). If NetBeans has problems with the M drive,
you can always save to your desktop or a USB drive.
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5. Ensure that the Create Main Class checkbox is checked.
6. Click Finish. Your project is displayed in the Project window and Main.java opens in
the Source Editor.
Changing some defaults
All options are found by clicking on Tools | Options. Changing some defaults
All options are found by clicking on Tools | Options.
Indentation
 Click on the Editor button at the top.
 Click on the Formatting tab.
 In the Language drop-down, click on Java.
 In the Category drop-down, click on Tabs and indents.
 Set Number of spaces per indent and Tab Size to 3. (You may have to turn off the
Use All Languages Settings check box.)
Braces
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Click on the Editor button at the top.
Click on the Formatting tab.
In the Language drop-down, click on Java.
In the Category drop-down, click on Braces.
Under Braces Placement, select New Line for all three options.
Under Braces Generation, select Generate for all four options.
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Change colors
 Click on the Fonts and Colors button at the top.
 Click on the Syntax tab.
 In the Language drop-down, click on Java.
 In the Category drop-down, click on Braces.
 Under Category, click on Comment.
 Under Foreground, click on the dropdown and select green (or Inherited was the
color on mine).
Turn on autocomplete for variables:
 Click on the Editor button at the top.
 Click on the Code completion tab.
 In the Language drop-down, click on Java.
 Turn on Auto Popup on Typing Any Java Identifier Part.
Other useful things to know
 If you have more than one project in your Projects list (left window), right-click and
choose Set as main project. NetBeans always runs your main project.
 The keyboard shortcut to run the main project is F6.
 The keyboard shortcut to "pretty-print" your source code is alt-shift-F.
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Java
Java is an object-oriented programming language. Almost everything in Java is an object.
The only data elements in Java that are NOT objects are the basic data types (called
primitives in Java). Java’s primitives are: integers, floating-point numbers, characters, and
Booleans. Everything else (including Strings and arrays) is an object.
Java is a relatively young programming language; it has been around since 1995. The best
way to learn how to write programs in a language is to read programs written in the
language.
2.2 Writing a Simple Program
Sample program (not same as textbook)
public class Sample001 {
public static void main (String args[])
{
int i = 100;
double x = 1.5;
boolean flag = true;
char middleInitial = 'X';
String firstName = "George";
String lastName = "Washington";
System.out.println (" Integer
System.out.println ("
Double
System.out.println ("
Flag
System.out.println ("Full name
" " + middleInitial + ". "
is: " + i );
is: " + x );
is: " + flag);
is: " + firstName +
+ lastName);
}
}
This program demonstrates:
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Basic structure of a Java program. Every program we write will be a class with a
public static void main procedure.
Every statement ends with a semicolon.
The beginning of a method (procedure/function) body is marked with a left curly
bracket ({) and the end is marked with a right curly bracket (}).
Basic types we will be using in this class:
 int
(also byte, short, and long)
 double
(also float)
 boolean (can be assigned true or false).
 char
We won't be using it very much. Note that single quotes are used to
enclose a char constant. Also note that characters in Java are
represented using Unicode (2 bytes per character).
 String
Note that "String" is capitalized and that it is NOT blue and bold like
the other data types! This is because it is not a "primitive" (built-in)
data type; it is a class/object. String constants are enclosed in double
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
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quotation marks. Java is case-sensitive!!!!! "String" is not the same
as "string"!
Variable declaration and initialization.
 Find out what happens when you don't initialize a variable. It used to be that
numbers are initialized to 0, Boolean to false, char to null character, and string to
empty string. Now, you get compile errors.
Output to the screen
To output to the screen, use System.out.print or System.out.println. The argument
(only one argument is allowed) to the print/println statements must be a string. You
can concatenate strings using the "+" sign. Numbers are automatically converted to
strings when used in a print or println statement ("a toString method is not
necessary).
2.3 Reading from the Console (later)
2.4 Identifiers
Naming Rules
Identifiers are used to name variables, constants, procedures and functions (called methods
in Java), classes, etc. All identifiers must follow the following rules:
 Must begin with a letter or an underscore (use a letter)
 Must be composed of letters, digits, underscores, and dollar signs (don't use dollar
signs – they are reserved for system use).
 Cannot be a keyword, a boolean literal, or the reserved word null.
 Are case-sensitive!
 It must be unique within its scope. A variable may have the same name as a variable
whose declaration appears in a different scope. In some situations, a variable may
share the same name as another variable if it is declared within a nested block of
code. (We will cover this in the next section, Scope.)
Naming Conventions
Variable names and method names: begin with a lowercase letter. If a variable name
consists of more than one word, the words are joined together, and each word after the first
begins with an uppercase letter, like this: isVisible.
Constant names: all upper-case, with underscores used to separate multi-word identifiers.
Class names: begin with an uppercase letter.
The underscore character (_) is acceptable anywhere in a name, but by convention is used
only to separate words in constants (because constants are all caps by convention and thus
cannot be case-delimited).
2.5 Variables
Declaring a variable:
int i;
Declaring multiple variables:
double x, y;
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Declaring and initializing variables:
double x = 10, y = 20;
Variables in Java may be either primitive or reference.
A primitive variable actually holds its data in the memory location that the variable refers
to. Primitive data types are:
 Integer types: byte (1), short (2), int (4), long (8 bytes)
 Floating point types: float (4 bytes), double (8 bytes)
 Character: char (implemented as 16-bit Unicode)
 Boolean: boolean (can only take on the values true and false)
Keyword
Description
Size/Format
(integers)
byte
Byte-length integer
8-bit two's complement
short
Short integer
16-bit two's complement
int
Integer
32-bit two's complement
long
Long integer
64-bit two's complement
(real numbers)
float
Single-precision floating point
32-bit IEEE 754
double
Double-precision floating point
64-bit IEEE 754
(other types)
char
A single character
16-bit Unicode character
boolean
A boolean value (true or false)
true or false
In this class, we will always use int when we need an integer type (unless we need a value
larger than 2 billion) and double when we need a floating-point type.
A reference variable holds the address of the data that it refers to. All objects are
reference variables.
 The String type is an object in Java, and therefore all strings are reference
variables.
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Variable Initialization
Local variables and member variables can be initialized with an assignment statement when
they're declared. The data type of the variable must match the data type of the value
assigned to it. Here are some examples, with the initialization code set in red:
public static void main(String[] args)
{
// integers
byte largestByte = Byte.MAX_VALUE;
short largestShort = Short.MAX_VALUE;
int largestInteger = Integer.MAX_VALUE;
long largestLong = Long.MAX_VALUE;
// real numbers
float largestFloat = Float.MAX_VALUE;
double largestDouble = Double.MAX_VALUE;
// other primitive types
char aChar = 'S';
boolean aBoolean = true;
System.out.println("Largest byte: " + largestByte);
System.out.println("Largest short: " + largestShort);
System.out.println("Largest integer: " + largestInteger);
System.out.println("Largest long: " + largestLong);
System.out.println("Largest float: " + largestFloat);
System.out.println("Largest double: " + largestDouble);
System.out.println("Character: " + aChar);
System.out.println("Boolean: " + aBoolean);
}
Parameters and exception-handler parameters cannot be initialized in this way. The
value for a parameter is set by the caller.
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