dart语言学习（十三）— 控制流语句

• 条件语句

  if 语句

  if…else if语句

  if…else if…else语句

void main(List<String> args) {
  int score = 60;
  if (score > 90) {
    print("优秀");
  } else if (score > 60) {
    print("良好");
  } else if (score == 60) {
    print("及格");
  } else {
    print("不及格");
  }
}

及格
Exited

• 循环语句

  for循环

  for…in循环

void main(List<String> args) {
  var list = [1, 2, 3, 4, 5];
  for (var index = 0; index < list.length; index++) {
    print(list[index]);
  }
  print("-----------------------------------------");
  for (var item in list) {
    print(item);
  }
}

1
2
3
4
5
-----------------------------------------
1
2
3
4
5
Exited

• while语句

  while循环

  do…while循环

void main(List<String> args) {
  int count=0;
  while(count<5){
    print(count++);
  }
  print("--------------$count---------------");
  do{
    print(count--);
  }while(count>-3&& count<5);
}

0
1
2
3
4
--------------5---------------
5
4
3
2
1
0
-1
-2
Exited

• break和continue

  终止循环：break

  跳出当前循环：continue

void main(List<String> args) {
  var list = [1, 2, 3, 4, 5];
  for (var item in list) {
    if (item == 2) {
      break;
    }
    print(item);
  }
  print("------------------------");
  for (var item in list) {
    if (item == 2) {
      continue;
    }
    print(item);
  }

  print("------------------------");
  var list2=[9,8,7];
  for (var item in list) {
    for (var item2 in list2) {
      if(item2==8){
        break;
      }
      print(item2);
    }
  }
}

1
------------------------
1
3
4
5
------------------------
9
9
9
9
9
Exited

• switch…case语句

  比较类型：num ，String ，编译期常量，对象，枚举

  非空case必须有一个break

  default处理默认情况

  continue跳转标签(特有，其他语言少见)

void main(List<String> args) {
  String language = "H5";
  switch (language) {
    case "Dart":
      print("---------Dart-------");
      break;
    case "H5":
      print("---------H5-------");
      break;
    default:
      print("-----none------");
      break;
  }
  print("-------------------------------");
  switch (language) {
    case "Dart":
      print("---------Dart-------");
      break;
    case "H5":
      print("---------H5-------");
      continue D;
    D:
    case "JAVA":
      print("---------JAVA-------");
      break;
    default:
      print("------none-----");
      break;
  }
}

---------H5-------
-------------------------------
---------H5-------
---------JAVA-------
Exited