var const final
num:int 和 double extends num
String:单引号或者双引号创建字符串
三引号或者双引号创建多行字符串
r 原始raw字符串
List:

var list = [1,2,3];
var list = const[1,2,3];
var list = new List();

Map:

var language = {'first':'Dart', 'second':'Java'};
var language = const{'first':'Dart', 'second':'Java'};
var language = new Map();

dynamic:

赋值运算符: ??=

int a = 10;
int b;
b ?? = 10;//b如果是空的，那就b就是10，b不空就用原来的值
//现在b是10
b ?? = 100；
//现在b还是10