用dart 语言实现一个简单的stack（栈）。代码如下：
class Stack<E> {
final List<E> _stack;
final int capacity;
int _top;
Stack(this.capacity)
: _top = -1,
_stack = List<E>(capacity);
bool get isEmpty => _top == -1;
bool get isFull => _top == capacity - 1;
int get size => _top + 1;
void push(E e) {
if (isFull) throw StackOverFlowException;
_stack[++_top] = e;
}
E pop() {
if (isEmpty) throw StackEmptyException;
return _stack[_top--];
}
E get top {
if (isEmpty) throw StackEmptyException;
return _stack[_top];
}
}
class StackOverFlowException implements Exception {
const StackOverFlowException();
String toString() => 'StackOverFlowException';
}
class StackEmptyException implements Exception {
const StackEmptyException();
String toString() => 'StackEmptyException';
}
void main() {
var stack = Stack<int>(10);
for (var i = 0; i < stack.capacity; i++) stack.push(i * i);
print(stack.top);
var sbuff = StringBuffer();
while (!stack.isEmpty) sbuff.write('${stack.pop()} ');
print(sbuff.toString());
}
