java - 在同一个Java数组中调用扩展类函数

Question

我有两个类 LoanBook 和 STLoanBook，STLoanBook 是 LoanBook 的扩展。它们都在同一个数组中:

private static final LoanBook[] books = new LoanBook[50];
books[0] = new STLoanBook("B129", "Soil Mechanics", "Engineering");
books[1] = new LoanBook("B238", "Basic Biology", "Science");
books[2] = new LoanBook("B563", "Company Law", "Business");
books[3] = new STLoanBook("B342", "Cost Accounting", "Business");
books[4] = new LoanBook("B754", "Robotics", "Engineering");

我试图调用仅在 STLoanBook 中的函数reserve()，当我通过for循环调用它时，它告诉我reserve()不存在，因为它正在检查LoanBook类。我该如何解决这个问题，因为我已经有循环检查类 SimpleName()，但它似乎仍然错误。救命!

Answer 1

您可以在 for 循环中使用 instanceof 运算符和casting，例如

    for (LoanBook book : books) {
        if (book instanceof STLoanBook) {
            ((STLoanBook)book).reserve();
        }
    }