Lecture 1 Introduction to Java
- Machine language -->Assembly language --> High-level language
A computer can execute the code in machine language.
A program written in a high-level language is called a source code/program, which the computer cannot understand, so the translation can be done using another programming tool called an interpreter or a compiler.(解释器和编译器）
interpreter: 逐行读取代码，翻译code，慢
compiler: 一次性翻译成机器语言，在执行，快
Java is an object-oriented programming language.
Java API contains predefined classes and interfaces for developing Java programs.
Every statement must end with a semicolon.
A block in enclosed inside braces.
在java中，compiler: javac
interpreter: java
source code --> compiler(javac) --> generate class(translate to java bytecode) --> interpreter(java) (using java virtual machine) --> executed
print 的用法：
print（）----不换行
println（）---换行
comments的几种方法：
// 仅限一行
/..../
/**...*/
identifiers:标识符（命名的名字）
must start with a letter, underscore(_) or a dollar sign $
不以数字开头，不以关键字命名
Named constants: 名字quanbudaxie
Programming error types:
Syntax error(Compile error) : mistype... didn't compile well （语法错误）
Runtime error: 非语法错误，是compile之后运行过程中的错误，eg out of bounds...
Logic error: produce incorrect result
Lecture 2 Numbers and Mathematics
Numerical data types: double > float > long > int > short > byte
long : -2^63 to 2^63-1 64 bit
int: -2^31 to 2^31-1 32 bit
short: -2^15 to 2^15-1 16 bit
byte: -128 to 127 8-bit
Numeric operators: + - * / %(remainder)
Augmented assignment operators: += -= *= /= %= 增强赋值运算符
double are more accurate than float
0.3333333333333 double
0.333334 float
如果float number涉及到了计算，所储存的数据都不是精确的
整数/整数，自动断截小数部分，不会rounded
++var先自身增加，再赋值
var++ 先赋值，在自身增加
Conversion rules:
隐式转换：如果计算中出现范围最大的数据，其他所有数据类型自动转换成出现最大范围的数据类型
强制转换： （int)3.9 >>>3
Operator precedence: 运算符优先级
（）var++ var--
++var --var
隐式转换 强制转换 type casting
- / %
= < <=
== !=
^
&&
| |
增强赋值运算符
同级运算符从左往右yunsuan
赋值运算符（Assignment operators以等号为核心)： 从右往左
专业术语： semicolon；reserved words；comments；blocks；braces{ }; parentheses ( ); brackets [ ] ; double slashes// ; quotation marks" " ;