Java_ identifiers, keywords, data types

Identifiers consist of a letter, an underscore "_", a dollar symbol "$", or a number;

Identifiers should be preceded by letters, underscores "_", and dollar breaks;

Java identifiers are case sensitive and have unlimited length.

All keywords are lowercase english;

Goto and const are not used, but are also reserved.

Constant

Character constant ' a '

string constant "Hello World"

Variable

is a small area of memory that uses variable names to access the area, so each variable must be declared before it is used, and then it must be assigned before it can be used.

Double D1, d2, d3 = 0.123;

Member variables

Local variables

Data type

Underlying data type

The logical Boolean True/false cannot be replaced with integers of 0 or not 0

Text Char Java is Unicode encoded, with two bytes per character, so it can be represented in hexadecimal notation

Integer type Byte,short,int,long

Floating-point float double

Floating-point Precision * Float 7-bit double 15-bit

Java_ identifiers, keywords, data types