Java Learning notes-identifiers, data types, floating-point numbers, character types, booleans, type conversions

Identifier:

Start with a letter, underscore (_), dollar sign ($)

You cannot use keywords

Case sensitive

You can divide int a = 1_0000_0000_1121 with an underscore;

Data type:

int defaults to decimal, octal starts with 0, Hex starts with 0x

SYSTEM.OUT.PRINTLN (*) Default output decimal

* at Integer.tobinarystring ()-and binary; octal (octal); Hex (hex)

If the size of the data does not exceed Byte/char/short's stated range, it can be automatically transformed ☆1

Long int constant at the end plus L

Floating point number:

Floating-point constants default double, turn float at the end plus F

There are rounding errors, such as the need for high precision error-free, using the BigDecimal class; Long->biginteger

Character type:

Because Java uses Unicode, it allows you to assign a Chinese character to a char variable

Strings string

Boolean:

Boolean

Type conversions:

☆1

Binary operations Generate type promotion

Java Learning notes-identifiers, data types, floating-point numbers, character types, booleans, type conversions