Chapter 2 Language Fundamentals

Chapter 2 Language Fundamentals

1. Encoding sets

   • ASCII
     • 127 characters
     • Each character is 7 bits
     • Java uses it for almost all input elements
   • Extended ASCII
     • Had more characters from other languages
     • Each character is 8 bits
   • Latin-1
     • Had characters for all latin based letters
     • Also had 8 bits per character
   • Unicode
     • Exists to encode all characters from almost all different languages into one set
       • Most widely used encoding set
     • 32 bits per character

2. Primitives

   • byte
     • any whole number between -2e7 and 2e7 - 1
     • takes up 8 bits
   • short
     • takes up 16 bits
     • any whole number between -2e15 and 2e15 -1
   • int
     • takes up 32 bits
     • any whole number between -2e31 and 2e31-1
   • float
     • takes up 32 bits
     • smallest positive nonzero = 14e-45
     • largest positive nonzero = 3.4028234e38
   • long
     • takes up 64 bits
     • any whole number between -2e63 and 2e63-1
   • double
     • takes up 64 bits
     • smallest positive nonzero number = 4.9e-324
     • largest positive nonzero number = 1.7976931348623157e308
   • char
     • A single unicode character
   • boolean
     • true or false

3. Variables

   • Data Placeholders
   • Every variable must have a declared type
     • Reference type uses referred object as datatype
     • Primitive type uses primitive datatype
   • Java variables also need an identifier to distinguish from other variables when referencing
     • Unlimited length sequence of java letters and java digits
       • Java digits include ASCII digits 0-9
     • Must begin with a java letter
       • Java letters include uppercase and lowercase ASCII latin letters A-Z
       • /u in front of a number denotes a unicode character
     • Must not be a keyword like boolean or null
   • You can also assign a value to a variable while declaring the variable
   • Variable names follow camel convention

4. Constants

   • variables whose values don't change once assigned
   • Declare by using keyword final
   • By convention, constants are in all uppercase with words separated by underscores
     • ex: final int ROW_COUNT = 50;

5. Literals

   • Integer literals
     • can be written in base 10, base 16, or base 8
     • Hexadecimal integers (base 16) are written with prefix 0x or 0X
     • Octal numbers are prefixed with a 0
     • Used to assign value to byte, short, int and long type variables
     • To assign a value to a long, suffix the number with L or l
     • Can be expressed in binary by prefixing number with 0B or 0b
   • Floating point literals
     • Parts of a floating point number
       • whole number part
       • a decimal point
       • A fractional part
       • An optional exponent part
         • the exponent part can be represented as either an e or an E
     • 2 types of floating points
       • double
         • larger numbers (64 bits in size)
       • float
         • Smaller numbers (32 bits in size)
     • ex: Digits . [digits] [exponentPart] f or F
       • f or F at the end makes the number a float otherwise it'd be a double
         • You can explicitly express a double too
           • suffix number in same format with a d or D instead of f or F
       • exponent part is always formatted as "ExponentIndicator SignedInteger"
         • Exponent indicator = e or E
         • SignedInteger = plus or minus sign and a digit
   • Character literals
     • Any unicode character enclosed in ' '
     • Escape sequence
       • \b = backspace key
       • \t = tab key
       • \\ = the backslash key
       • \' = single quote
       • \" = double quote
       • \n = linefeed
       • \r = enter key
   • Boolean literals
     • either "true" or "false"

6. Java Separators

   • Parenthesis ( )
   • Brackets [ ]
   • Braces { }
   • Angle brackets < >
   • Semicolon ;
   • colon :
   • Comma ,
   • Period .