Language Fundamentals-OOP

Language Fundamentals-OOP

1. encoding sets-

   • Unicode
     • Unicode Consortium--all language into single character set
       • One unique number for one character,16b for each, 65000 + characters, ideal 32b system for storing
       • encoding making it efficient
         • UTF8-popular for HTML, having the same byte value as ASCII
         • UTF16- all the commonly used characters fit in and the less used ones fit in pairs of 16-byte code units
         • UTF32-32 bits for every single character, not a choice for the Internet with present technology
     • for writing comments, identifiers, contents with string and characters, can be in a language other than English
   • ASCII-American Standard Code for Information Interchange
     • can be written by any human language
       • only for alphanumeric
         • Upper & lower case Latin letters, numbers, punctuation marks---7b for each, 128 characters
       • extended ASCII
         • special symbols, letters in other languages,---8b for each, 128 characters
       • Different languages use different character sets
     • Java use ASCII for almost all the input values
   • Primitives: non-object programming elements
     • numbers/ simple values like T/F
   • variables-content can change
   • constant-values cannot change
   • literals-representation of data values understood by Java compilers
   • primitive conversation-changing a primitive from one type to another type
   • operators-notations that certain operations will happen

2. Seperators

   • ( ) parenthesis: method signature for list of arguments; to raise operator precedence; to narrow conversations;l oops to contain expressions
   • { } brakes: declaration of types; blocks of statement; array initialization
   • [ ] brakets: array dereferencing; array declaration
   • to pass parameters to parameterized types
   • ; semicolon: terminate statement; in the for statement, to seperate initialization code, expressions, update code
   • : colon:
     • in the for statement, iterates over an array or a collection
   • , comma: seperate arguments
   • . period: to seperate package names from subpackages and type names; to seperate a field or method from rederence viarable
   • <> angle brackets: pass parameter to parameterized types

3. Primitives- another Java data type other than objects, for "speed", saving CPU. always using the smallest possible data size for saving memory

   • bytes-8bits integer -128 (-2^7)~127 (2^7-1)
   • short- short integer 16 bits -32768 (-2^15) ~32767 (2^15-1)
   • int- integer 32 bits -2^31 ~ 2^31-1
   • long-long integer 64 bits -2^63 ~ 2^63-1
   • float-single precision float point, 32bits, nonzero 14e^-45 ~ 3.4028234e^38
   • double- decimals, double precision float point, 32bits, nonzero 4.9e^-324 ~ 1.7976931348623157e^308
   • char- Unicode character, "a", "9", "&", "的“, ...
   • boolean- logic, T/F

4. variables-data placeholders, must have declared type

   • reference types-reference to an object
   • primitive types- hold a primitive
   • identifier-unlimited length sequence, must not be a keyword, within its scope

5. operations--binary, only 0 &1 reverse if negative

   • cannot start with a number or have "+" in it

6. coding

   • declare variable first, write their type front, seperate with comma, naming: lower case first letter the rest capitalize
   • constant: value cannot change after assigning, all capitalized seperated by _
   • literals eg. char int
     • integral literals: int, short, long, byte
       • hexadecimal integral begins with 0x or 0X
       • octal integrals begin with 0
       • long: suffix with L or I
       • can be prefixed 0b or 0B
     • String literals: String
     • null
   • floating-point literals: eg. 0.4 , 0.5e^10, decimal& optional exponent , for the whole number part 0 is optional
     • float- 32bits, f_ or _F, [] , +optional
     • double 64 bits, d_ pr _D, [], + optional
   • boolean: T/F declaration: write boolean first the variable name, assign it true or false
   • character literals - Unicode characters & escape sequence
     • characters: 'A' '好'
     • escape sequence: "\n"-linefeed, "\\" backlash , "\'"-single quote "\""-double quote "\t' tab "\b" backspace "\r" carriage return