Java Fundamentals 1

Java is an explanatory language {Introduction to efficient cross-platform (write once run anywhere at a time)}java virtual machine >java compiler > bytecode files---*.class----class loader

is a purely object-oriented language {encapsulates inheritance polymorphism}

James Gosling (1990 Writing language (oak--oak))

1995 improved form Java----jdk1.0

Identifier
Whatever you need to name yourself is called an identifier.

Code specification:
1. Identifiers may consist of letters (uppercase and lowercase), _, $, and cannot start with a number

2. Declarations of all variables and methods must be made to be known

3. Hump naming Method (first letter lowercase, the remaining words capitalized)
getElementById ()
4. Any operator must have a blank on both sides

5. Class name first letter must be capitalized

Java Basic data type:

Four class eight (underlying data type):
integer
            byte    2 8-way      1 bytes
            short    2 16-Time Square      2 bytes
            int    2 32-Time Square      4 bytes
            long    2 64-Time Square      takes 8 bytes of

Floating point Type
Float number of significant digits 7 bits accounted for 4 bytes
Double significant digits 16 bits 8 bytes

Boolean type
Boolean True/false of 1 bytes
Character type
Char 0-65535% of 2 bytes

String type (not part of data type)
String

Reference type:
All the classes
All the interfaces
All the arrays
Null

Java Fundamentals 1