【初见Dart】第三章:运算符

1. 算数运算符

1.1 概述

- 加减乘除: + ,- ,* ,/ ,~/ , %
- 递增递减: ++var ,var++ ,--var ,var--

1.2 代码示例

void main() {
  int a = 10;
  int b = 2;
  print(a + b); //12
  print(a - b); //8
  print(a * b);//20
  print(a / b);//5.0
  print(a ~/ b);//5
  print(a % b);//0
  print(a++); //10 a=10-> print-> a=11
  print(++a); //12 a=11-> a=12-> print
  print(a--); //12 a=12-> print-> a=11
  print(--a); //10 a=11-> a=10-> print
}

2. 关系运算符

2.1 概述

- 运算符:==, !=, >, <, >=, <=
- 判断内容是否相同使用==

2.2 代码示例

void main() {
  int a = 5;
  int b = 3;

  print(a == b); //false
  print(a != b); //true
  print(a > b); //true
  print(a < b); //false
  print(a >= b); //true
  print(a <= b); //false

  String strA = "123";
  String strB = "123";
  print(strA == strB); //true 比较内容
}

3. 逻辑运算符

3.1 概述

- 运算符: !, &&, ||
- 针对布尔类型运算

3.2 代码示例

void main() {
  bool isTrue = true;
  print(!isTrue); //false

  bool isFalse = false;
  print(isTrue && isFalse); //false
  print(isTrue || isFalse); //true

  String str = "";
  print(!str.isEmpty); //false
}

4. 赋值运算符

4.1 概述

基础运算符: =, ??=
复合运算符: +=, -=, *= , /=, %= , ~/=

4.2 代码示例

void main() {
  var a = 10;
  int b = 10;
  var c = null;
  c ??= 10;
  print(c); //10 相当于kotlin中的 c?.(operate)?:10

  a += 2;
  print(a); //12

  a -= b;
  print(a); //2

  a *= b;
  print(a); //20
  //a /= b;
  //print(a) //无法运算,因为结果是0.0会成为double类型,所以无法赋值给int类型的a
  a ~/= b;
  print(a); //2
  a % b;
  print(a); //2
}

5. 条件运算符

5.1 概述

三目运算符: condition ? expr1 : expr2
??运算符: expr1 ?? expr2

5.2 代码示例

void main() {
  int gender = 1;
  String str = gender == 0 ? "Male= $gender" : "Female= $gender";
  print(str); //Female= 1

  String a = "Dart";
  String b = "Java";
  String c = a ?? b;
  print(c); //Dart
}