Method overloading ： Same class , Same method name , Different parameters （ The number is different. , Different types , Different order ）, Determine whether to overload , Just look at the method name and parameters , Nothing to do with the return value .
IDEA View the method source code ：Crtl + Left mouse button
Java The default value is decimal
Binary system ： The value is preceded by 0b start ,b It can be in both case
octal ： The value is preceded by 0 start
Hexadecimal ： The value is preceded by 0X start ,x It can be in both case
Binary fast to decimal ：8421 code
Binary fast to octal ： Binary number 3 One by one , Work it out and put it together
Binary fast to hexadecimal ： Binary number 4 One by one , Work it out and put it together
The complement of positive numbers is the same
The inverse of a negative number ： The sign bits remain the same , The rest of the bits are reversed
A negative complement ： At the end of the inverse +1
<< Signed shift left operator ： The binary bit moves to the left , The left sign bit is discarded , Right side use 0 A filling . A few places to the left , It's times 2 To the powers of
Signed shift right operator ： The binary bit moves to the right , Use sign bits to complement . Move a few to the right , Is divided by 2 To the powers of
Unsigned shift right operator ： No matter the sign bit is 0 still 1, It's all used 0 Fill in the space .
Class composition ： Attributes and behaviors
Member variables ： Variables outside methods in a class , There are default initialization values
local variable ： Variable in method , Including formal parameters , No default initialization value
private keyword ： Permission modifier , You can modify members , characteristic ： Can only be accessed in this class .
this： Identify member variables （ When a local variable has the same name as a member variable ,java Will use the principle of proximity ）
this Represents the object reference of the class , Method is called by which object ,this On behalf of the object
Construction method ： Called when an object is created , Call once , Execute the construction method once ; Constructors cannot be called manually .
The method name is the same as the class name , The case should also be consistent
no return value , even void either
No specific return value （ Not by return Return results ）
If no constructor is written in the class , The system will provide a parameterless construction method
JavaBean class ： Encapsulated data