Dart列表-Dart List.single方法

List.single

void main() {
var lst = new List();
lst.add(12);
print("The list has only one element: ${lst.single}");
}

The list values in reverse order: (13, 12)

The list has only one element: 12

void main() {
var lst = new List();
lst.add(12);
lst.add(10);
print(lst.single);
}

Unhandled exception:
Bad state: Too many elements
#0 List.single (dart:core-patch/growable_array.dart:234)
#1 main (file:///D:/Demos/Boolean.dart:6:13)
#2 _startIsolate.<anonymous closure> (dart:isolatepatch/isolate_patch.dart:261)
#3 _RawReceivePortImpl._handleMessage (dart:isolatepatch/isolate_patch.dart:148)