Dart语言switch case示例

void main() { 
   var grade = "A"; 
   switch(grade) { 
      case "A": {  print("Excellent"); } 
      break; 

      case "B": {  print("Good"); } 
      break; 

      case "C": {  print("Fair"); } 
      break; 

      case "D": {  print("Poor"); } 
      break; 

      default: { print("Invalid choice"); } 
      break; 
   } 
}