• 表示式

  三目表示式：condition? expr1:expr2

  ??運算子：expr1:expr2

• 案例

void main(List<String> args) {
  int gender = 1;
  String str = gender == 0 ? "Male" : "Frmale=$gender";
  print(str);

  String a;
  String b = "java";
  String c = a ?? b;
  //a為空的時候列印b，a不為空是列印a
  print(c);

  a = "huang";
  b = "java";
  c = a ?? b;
  print(c);
}
 

Frmale=1
java
huang