How Can I Efficiently Iterate Through a Java ResultSet and Extract Data?

Java: Iterating through Result Sets Effectively

In Java, working with database result sets is a common task when retrieving data from a database. In this article, we will explore an efficient approach to loop through the records in a result set and extract specific values.

Consider the following example:

String querystring1 = "SELECT rlink_id, COUNT(*)"
                   + "FROM dbo.Locate  "
                   + "GROUP BY rlink_id ";

This query retrieves the unique rlink_id values along with their respective counts from the dbo.Locate table. Assuming you have executed this query and obtained a ResultSet object (rs4), the next step is to extract the values.

The original code provided,

String[] show = {rs4.getString(1)};
String[] actuate = {rs4.getString(2)};

only retrieves and displays the first record in the result set. To iterate through all the records, we can use a while loop in conjunction with the rs4.next() method.

To improve the approach, let's introduce two lists, sids and lids, which will store the values of rlink_id and the counts, respectively.

List<String> sids = new ArrayList<String>();
List<String> lids = new ArrayList<String>();

The modified code becomes:

while (rs4.next()) {
    sids.add(rs4.getString(1));
    lids.add(rs4.getString(2));
}

Finally, we can convert the lists into arrays to display the data as desired:

String[] show = sids.toArray(sids.size());
String[] actuate = lids.toArray(lids.size());

This improved approach efficiently loops through the entire result set, extracting the desired values and storing them in separate lists. These lists can then be easily converted into arrays for further processing or display.

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