lesson02_ variables and data types

A variable

　　1. Identifier

　　2. Keyword

　　3.Java naming rules

　　4. Constant

　　5. Variables

Second, the data type

　　1. The basic data types

　　2. The reference data types brief

Third, the conversion between the number of decimal

　　1. The conversion between binary and decimal

　　2. Conversion between decimal and octal

　　3. Other conversion between hexadecimal number

Fourth, the keyboard input Scanner