如何有效檢查Java結果集是否為空？

Checking for Empty Result Sets in Java

Result sets in Java provide a means to iterate over database query results. However, the absence of a hasNext() method poses a challenge in determining if a result set contains any data.

One common approach is to use the next() method, which advances the cursor to the next row and returns true if successful:

if (!resultSet.next()) {
    System.out.println("no data");
}

While this approach works, it requires iterating through the entire result set, even if it's empty.

A More Efficient Approach

The Java ResultSet class provides a more efficient way to check if there are any results without advancing the cursor. The isBeforeFirst() method returns true if the cursor is before the first row or if the result set is empty:

if (!resultSet.isBeforeFirst()) {
    System.out.println("No data");
}

This approach avoids unnecessary iteration and provides a concise way to determine the presence of data in a result set.

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