This indicates that the BankAccount class is an abstract class and the withdrawal method is an abstract operation.

这表示，BankAccount类是一个抽象类，而withdrawal方法是抽象的操作。

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This indicates that the BankAccount class is an abstract class and the withdrawal method is an abstract operation.

这表示，BankAccount类是一个抽象类，而withdrawal方法是抽象的操作。

youdao