note_java

1. compile

- javac XXX.java -> compile -> hexa(bytecode), nema.class
- java XXX : excute file 




2. data type
	1) Primitive : store data(value) into memory
		- byte(1bytes = 8bits = 8 slots) _ _  _  _  _  _  _  _ (binary ) decimal x
		- short(2bytes)
		-* int(4bytes)
		- long(8, 64 bit)
		-* char(a character, 1 byte)
		- float(10.2f 32bit)
		-* double(10.24	64bits) - more precise
		-* boolean( )

		#	2^0 + ...+ 2^n = 2^(n+1)-1
		#	minus
			8bit -> use only 7bit.
				first bit : 1 --> -
				first bit : 0 --> +

				01111111 : 127
				10000000 : -128
				11111111 : -1

				10000001
				


	2) Reference : store reference(location)


3. run or import
	1) run
		- have to have MAIN function

	2) import
		-


4. JVM
			 (bytecode)	
	.Java -> .class -> 
		compile 	JVM(SW)


5. errors 
	1) Compile -time error : red underline
		- syntax, 
	2) Run-time error : after run your program, hard to fix


6. conditional statements
	- if - else <-- JS
	- swich - case

7. loops : for, while 
	- break	:	stop 
	- continue :	skip


8. operator

	 + - * / % ++ --
	 && || !

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1. Object Oriented
							class			Car
	1) state(attributes) -> variables 		color, doors, type
	2) behaviors(Action) -> methods			drive(), park(), break()


	class---
	|		|-> car1(object, instance) : has different 1),2) 
	|Car	|-> car2
	---------
	blueprint(declear)

	- constructor is a method to create instance : initialize variables
	- Car myCar = new Car(1,1,1,1) 
	  type var = new constructor

	- instances 
		: self contained code, variable, object
		: New custom data type