// Define a new SQL SELECT statement.
String sql_string = "SELECT column1, column2 FROM SampleTable";

// Create a new PreparedStatement from an existing connection.
PreparedStatement ps = conn.prepareStatement(sql_string);

// Create a new ResultSet to contain the query results of the SQL statement.
ResultSet rs = ps.executeQuery();

// Check if the PreparedStatement contains a ResultSet.
if (ps.hasResultSet()) {
     // Retrieve the column1 value from the first row using getString.
     String row1_col1 = rs.getString(1);
     // Get the next row in the table.
     if (rs.next()) {
          // Retrieve the value of column1 from the second row.
          String row2_col1 = rs.getString(1);
     }
}

rs.close();
ps.close();

PreparedStatement ps = conn.prepareStatement("SELECT id FROM t");
ResultSet rs = ps.executeQuery();
List<Integer> l = new ArrayList<Integer> ();

while(rs.next()) {
    l.add(rs.getInt(1));
}
rs.close();
ps.close();