不要关闭setConnection()中的扫描仪teclado.关闭扫描程序也会关闭其关联的流.然后在askToDo中，当您创建另一个扫描仪时，System.in已经关闭.

Don't close the Scanner teclado in setConnection(). Closing a Scanner also closes its associated stream. Then in askToDo, when you create another Scanner, System.in is already closed.

您应该有一个用System.in初始化的***静态Scanner对象，并在类中的任何地方使用该对象，而不是在每个方法中创建一个新的Scanner.

You should have a single top-level static Scanner object, initialized with System.in, and use that everywhere in your class instead of creating a new Scanner in each method.