Why is this an issue?
There are several reasons to avoid using this method:
- It is optionally available only for result sets of type
ResultSet.TYPE_FORWARD_ONLY. Database drivers will throw an exception if
not supported.
- The method can be expensive to execute as the database driver may need to fetch ahead one row to determine whether the current row is the last
in the result set. The documentation of the method explicitly mentions this fact.
- What "the cursor is on the last row" means for an empty
ResultSet is unclear. Database drivers may return true or
false in this case .
ResultSet.next() is a good alternative to ResultSet.isLast() as it does not have the mentioned issues. It is always
supported and, as per specification, returns false for empty result sets.
How to fix it
Refactor your code to use ResultSet.next() instead of ResultSet.isLast(). Be cautious of its different semantics and side
effects on cursor positioning in the result set. Verify that your program logic is still valid under these side effects and otherwise adjust it.
Code examples
Noncompliant code example
ResultSet results = stmt.executeQuery("SELECT name, address FROM PERSON");
StringBuilder sb = new StringBuilder();
while (results.next() && !results.isLast()) { // Noncompliant
sb.append(results.getString("name") + ", ");
}
sb.append(results.getString("name"));
String formattedNames = sb.toString();
Compliant solution
ResultSet results = stmt.executeQuery("SELECT name, address FROM PERSON");
List<String> names = new ArrayList<>();
while (results.next()) { // Compliant, and program logic refactored
names.add(results.getString("name"));
}
String formattedNames = names.stream().collect(Collectors.joining(", "));
Resources
Documentation
