What is ResultSet in Java: Explanation and Example

ResultSet in Java is an object that holds data retrieved from a database after executing a query. It acts like a table of data you can move through row by row to read the results.

How It Works

Imagine you ask a librarian for a list of books matching your search. The librarian gives you a printed list you can read one line at a time. In Java, when you ask a database for data using a query, the ResultSet is like that printed list. It holds all the rows of data returned by the database.

You can move through this list one row at a time using methods like next(). For each row, you can get the values of columns by their names or positions. This way, you can process or display the data as needed.

Example

This example shows how to connect to a database, run a query, and use ResultSet to read and print the data.

java

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;

public class ResultSetExample {
    public static void main(String[] args) {
        String url = "jdbc:sqlite::memory:"; // Using in-memory SQLite database
        try (Connection conn = DriverManager.getConnection(url);
             Statement stmt = conn.createStatement()) {

            // Create a sample table
            stmt.execute("CREATE TABLE users (id INTEGER, name TEXT)");
            // Insert sample data
            stmt.execute("INSERT INTO users (id, name) VALUES (1, 'Alice'), (2, 'Bob'), (3, 'Charlie')");

            // Query the table
            ResultSet rs = stmt.executeQuery("SELECT id, name FROM users");

            // Loop through the ResultSet
            while (rs.next()) {
                int id = rs.getInt("id");
                String name = rs.getString("name");
                System.out.println("User ID: " + id + ", Name: " + name);
            }

        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Output

User ID: 1, Name: Alice
User ID: 2, Name: Bob
User ID: 3, Name: Charlie

When to Use

Use ResultSet whenever you need to read data from a database after running a query. It is essential for applications that work with databases, such as websites, desktop apps, or mobile apps that show stored information.

For example, if you want to display a list of users, products, or orders stored in a database, you run a query and use ResultSet to get and process that data row by row.

Key Points

• ResultSet holds data returned by a database query.
• You move through rows using next().
• Access column data by name or index.
• Always close ResultSet and related resources to avoid leaks.
• Works with Statement or PreparedStatement objects.

Key Takeaways

ResultSet stores data retrieved from a database query in Java.

Use next() to move through rows and get data by column name or index.

ResultSet is essential for reading and processing database query results.

Always close ResultSet and database resources after use to free memory.