java - 如何返回对象数组的索引？

Question

尝试返回索引时出现错误(必须返回一个整数)，我看不出我做错了什么。如何将 Object 数组索引与 int 进行比较，并返回索引号？

//x starts at 10000 because the left most number is assumed to be at least a 1.
/**
 * Search for a book id within the Book object array
 * @param Book - Array of objects with book id, title, isbn, author, and category
 * @param numOfBooks - how many books are in the library
 * @param myBookID - The key to search for
 * @return the index of the array where the key matches
 */
public static int bookSearch (Object[] Book, int numOfBooks, int myBookID) {
    for (int x = 10000; x <= numOfBooks; x ++)
        if (Book[x].equals(myBookID))
            return x;
}

Answer 1

你需要在最后添加一个额外的 return，因为你的 if 条件可能永远不匹配。

public static int bookSearch (Object[] Book, int numOfBooks, int myBookID) {
    for (int x = 10000; x <= numOfBooks; x ++) {
        if (Book[x].equals(myBookID))
            return x;
    }

    return -1;
}

附带说明一下，您可能想要检查数组的边界，而不是假设数组中最多有 10000 个项目。您还可以利用所有数组都有一个 length 属性这一事实，以避免传入您的参数之一:

public static int bookSearch (Object[] books, int myBookID) {
    if(books.length < 100000) return -1;

    for (int x = 10000; x <= books.length; x++) {
        if (Book[x].equals(myBookID))
            return x;
    }

    return -1;
}