Introduction%20to%20Java%20Programming

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Lecture 2

• Introduction to Java Programming

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Java Class Format
public class userDefinedName public static
void main(String args)
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2.2 Primitive Data Types
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Lexical Elements

• Keywords
• Literals
• Identifiers
• Operators
• Punctuation

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Keywords
abstract default if private this boolean
do implements protected throw break
double import public throws byte else
instanceof return transient case extends
int short try catch final interface
static void char finally long strictfp
volatile class float native super while
const for new switch continue goto
package synchronized

• Can not be used for any other purpose
• All lowercase letters

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Literal

• A literal is the source code representation of a
  value of a primitive type or the String type

Data type Literal Examples int -4501
double 35.271d char b
boolean true String Hello World
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Identifiers

• An identifier is an unlimited-length sequence of
  Java letters and Java digits, the first of which
  must be a Java letter. An identifier cannot have
  the same spelling as a keyword or boolean literal.

Example identifierssumprodroot1isLeapYear
QuadraticLeapYearMAX
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Operators
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Punctuation

• The following nine ASCII characters are the
  separators (punctuators) ( )
  , .

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White Space

• White space is defined as the ASCII space,
  horizontal tab, and form feed characters, as well
  as line terminators

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Comments

• There are two kinds of comments
• / text / A traditional comment all the text
  from the ASCII characters / to the ASCII
  characters / is ignored by the compiler
• // text A end-of-line comment all the text from
  the ASCII characters // to the end of the line is
  ignored by the compiler.

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All variables must be defined

• Tell the compiler the
• name of each variable
• type of each variable

int xint yboolean isLeapYearboolean
isPerflickdouble root1double root2
int x, yboolean isLeapYear, isPerflickdouble
root1, root2
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Initializing variables
int x 5int y //y need not be
initialized y 2x 1