1:java Technology Station
2: Graphic image
3: library lib.
4: Basic Package
5:jvm
6 Operating system
7 Computer Hardware
: Operating mechanism:
java========= "Java compilation ========". class file ======== "
. jar Package ========= "products to users
. jar Package ======= "operating system (including JVM industry standard) =======" jvm=====> native JVM directive
Four:
C + +: Is the direct generation of CPU instructions.
JAVA: Generate class file, compile by Javac, JIT Real-time editor.
: Data type:
Int 1 2 3 4
Float 1234.21335 (7 digits after the decimal point of the floating-point number)
Double 1234.12563 (doubles) 14 digits after the decimal point.
the presentation naming rules for Java:
1: Identifiers are composed of letter, underscore, and ($) dollar sign AA digits.
2: Identifiers should start with a letter, underscore, dollar sign.
Variables and constants:
Variable: Refers to a data type that can be rewritten at least once.
Constants: The amount of data that cannot be changed throughout the program, usually the variable names are capitalized. Eg:
Final int pi=10;
Several operators:
Arithmetic operators: +-*/%
Relational operator:< > = >= <=! =
Logical operators: $$ | |!
The Third Java Foundation
