Seeing JAVA-Data Type & Operation-03
Strongly typed language
java is a strongly typed language
basic type
byte 1B
short 2B
Int 4B
long 8B
float 4B (use with caution, about =)
double 8B
用BigDecimal
char 2B
String! is the class
boolean 1b
Reference type
Except 8 basic types are reference types
Forced conversion
High-low
overflow
Loss of accuracy
Automatic conversion
Low-high
variable
Class variable static
Instance variable: subordinate to the object, there is a default value if it is not initialized by itself, the default value of boolean is false, and the default value is null except for basic types
Local variables must be declared and initialized
constant
static final
Variable capitalization
Operator
When performing operations on different basic types of data
Convert long with long
Convert int without long
a++，++a
Auto-increment after executing the code
Bit operation
Extremely efficient
,<< *2
String concatenation+
The content has a string, it will become String
But there are operations in front of the string, and then it becomes a String
Ternary operator
X ？a；b
X judgment, true output a; false output b