6.1.2 Cursors

A ResultSet object maintains a cursor, which points to its current row of data. The cursor moves down one row each time the method next is called. When a ResultSet object is first created, the cursor is positioned before the first row, so the first call to the next method puts the cursor on the first row, making it the current row. ResultSet rows can be retrieved in sequence from top to bottom as the cursor moves down one row with each successive call to the method next. This ability to move its cursor only forward is the default behavior for a ResultSet and is the only cursor movement possible with drivers that implement only the JDBC 1.0 API. This kind of result set has the type ResultSet.TYPE_FORWARD_ONLY and is referred to as a forward only result set.

If a driver implements the cursor movement methods added in the JDBC 2.0 core API, its result sets can be scrollable. A scrollable result set's cursor can move both forward and backward as well as to a particular row. The following methods move the cursor backward, to the first row, to the last row, to a particular row number, to a specified number of rows from the current row, and so on: previous, first, last, absolute, relative, afterLast, and beforeFirst. An explanation and example of how to make a result set scrollable will be presented in the section "Creating Different Types of Result Sets" on page 74.

When a cursor is positioned on a row in a ResultSet object (not before the first row, after the last row, or on the insert row), that row becomes the current row. This means that any methods called while the cursor is positioned on that row will (1) operate on values in that row (methods such as the get and update methods), (2) operate on the row as a whole (methods such as updateRow, insertRow, deleteRow, refresh-Row), or (3) use that row as a starting point for moving to other rows (such as the method relative).
A cursor remains valid until the ResultSet object or its parent Statement object is closed.