Language Fundamentals

Language Fundamentals

1. Character Sets

   • ASCII (American Standard Code for Information Exchange)
     • 128 characters, each represented by 7 bits
       • includes lower case and upper case Latin letters, numbers, and punctuation marks
     • later extended to include another 128 characters, each represented by 8 bits; called extended ASCII
       • contains all the characters required for writing text in many western European languages
     • used in Java for input elements except comments, identifiers, and the contents of characters and strings
   • Unicode
     • attempts to include all characters in all languages in the world into one single character set
     • character encoding makes it more efficient to store and transmit Unicode text
       • UTF-8 UTF-16 UTF-32
     • supported in Java for comments, identifiers, and the contents of characters and strings

2. Separators

   • braces { }
   • brackets [ ]
   • angle brackets < >
   • semicolon ;
   • colon :
   • comma ,
   • period .
   • parentheses ( )

3. Primitives

   • numbers
     • byte short int long float double
   • single Unicode characters = char
   • true/false = boolean

4. Variables

   • data placeholders
   • reference types
     • provides a reference to an object
   • primitive types
     • holds a primitive
   • have identifiers (names)
     • unlimited length but must begin with a Java letter
     • cannot be a Java keyword, boolean literal, or null literal
     • must be unique within its scope
   • declare a variable by writing the type first, then the name plus a semicolon
   • first letter lowercase, subsequent words start in uppercase
   • constants
     • variables whose values don't change once they've been assigned
     • declared using the keyword final

5. Literals

   • primitive types
     • integer literals
       • can be written in decimal, hexadecimal, or octal
       • used to assign values to variables of types byte, short, int, and long
         • must not assign a value that exceeds the capacity of a variable
         • to assign a value to long, suffix the number with the letter L or l
     • floating-point literals
       • has the following parts: a whole number, a decimal point, a fractional part, and an optional exponent
       • float = 32 bits in size
       • double = 64 bits in size
     • character literals
       • Unicode character or an escape sequence
         • escape sequence - representation of a Unicode character that cannot be entered using the keyboard or that has a special function in Java
     • boolean literals
       • true or false
   • string
   • null