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"); 
   } 
}