Dart语言if...elseif...else语句实例

void main() { 
   var num = 2; 
   if(num > 0) { 
      print(${num} is positive); 
   } 
   else if(num < 0) { 
      print(${num} is negative); 
   } 
   else { 
      print(${num} is neither positive nor negative); 
   } 
}