第1章--用程序来做计算
1.1 第一个Java程序
Mac version: Preference -> General -> Keys -> Search "Content Assist" for binding to the short-key you want.
1.2 用变量做计算
1.3 表达式（浮点数，优先级和类型转换）
rounding happens to floating number: (e.g. shown below)
System.out.println(1.2-1.1);
output: 0.09999999999999987
第2章--判断
2.1 作比较
comparison between int and double:
int a = 5;
double b = 5.0;
System.out.println(a==b);
output: true
comparison between double and double:
int a = 5;
double b = 5.0;
System.out.println(a==b);
output: true
int a = 1.0;
double b = 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1;
System.out.println(b == c);
System.out.println(b+"; "+c);
output: false
output: 1.0; 0.9999999999999999
solution: Math.abs(a-b) < 1e-6;
2.2 判断语句
2.3 多路分支
第3章--循环
3.1 循环（while和do-while循环）
do-while syntax: (cannot image that I even do not remember this)
do {
// body
} while (condition);
3.2 for循环
3.3 循环控制（含复合赋值、逻辑类型）
using break with a label：similar to "goto" in c language
blahblahblah;
LABEL:
for(int i = 0; i < 10; i++) {
blahblahblah
if (...) {
break LABEL; // break the loop labelled "LABEL"
}
}
3.4 循环应用
tricks for integer processing:
得到个位数：%10
去掉最低位：/10
Formatted Print:
System.out.printf("%.2f", x);
第4章--数组
4.1 数组的创建和使用
syntax of defining and creating an array: // fine, haven't write Java for rly a long time
type[] name = new type[size]; // size could be a variable, but it must be provided
e.g: int[] i = new int[array_size];
with initialisation:
type[] name = new type[size];
e.g: int[] i = {1,2,3};
4.2 数组变量和运算
int[] a = new int[size];
initialise array a
int[] b = a; // b just points to the block data which a points to (same block of data)
a == b ? true
but what if a and b points to different blocks of memory?
int[] a = {1,2}；
int[] b = {1,2}；
a == b ? false
if we wanna compare the content of two arrays: solution--traversing and comparing each pair of element
if we wanna copy an array: solution--traversing and copying each element one by one
syntax for "for-each" loop to traverse an array:
for (type element: array) {}
4.3 二维数组
syntax for creating, initialising, and modifying a two-dimensional array:
int[][] a = new int[size][size];
int[][] a = { {1,2,3,4}, {1,2} };
a[1][2] = 5;
第5章--函数
5.1 函数的定义和调用
函数有多个出口（多个return statements）--> bad design
5.2 函数的参数与本地变量
Java在调用函数时，永远只能传值给函数（？）
life-cycle of a local variable: inside the block
e.g.
{ int i; } i = 0; // ERROR
（END）
