JDBC: PreparedStatement with Parameters

Java needs a JDBC driver at run time. Download sqlite-jdbc from Maven Central (org.xerial:sqlite-jdbc) and run: java -cp .:sqlite-jdbc.jar Main (on Windows use ; instead of :).

/*
 * Problem : Run the commands.
 * Input   : Input lines.
 * Output  : Output lines.
 * Approach: Parameterized query
 * Time    : O(n log n)
 * Space   : O(n)
 * Java    : 8 or newer.
 */
import java.util.Scanner;
import java.sql.*;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class Main {
    // This method solves the task. It receives the input and returns the answer.
    static String[] solve(String[] lines) {
        List<String> out = new ArrayList<String>();
        int minAge = Integer.parseInt(lines[lines.length - 1].split(" ")[1]);
        try (Connection conn = DriverManager.getConnection("jdbc:sqlite::memory:")) {
            try (Statement create = conn.createStatement()) {
                create.execute("CREATE TABLE people (name TEXT, age INTEGER)");
            }
            // Step 1: Prepare the INSERT once. addBatch collects the rows, and executeBatch sends them together.
            try (PreparedStatement insert = conn.prepareStatement("INSERT INTO people (name, age) VALUES (?, ?)")) {
                for (int i = 0; i < lines.length - 1; i++) {
                    String[] part = lines[i].split(" ");
                    insert.setString(1, part[0]);
                    insert.setInt(2, Integer.parseInt(part[1]));
                    insert.addBatch();
                }
                insert.executeBatch();
            }
            // Step 2: The filter value is passed with setInt. The database never reads it as SQL text.
            try (PreparedStatement select = conn.prepareStatement("SELECT name FROM people WHERE age >= ? ORDER BY age, name")) {
                select.setInt(1, minAge);
                try (ResultSet rs = select.executeQuery()) {
                    while (rs.next()) {
                        out.add(rs.getString(1));
                    }
                }
            }
        } catch (SQLException e) {
            throw new RuntimeException(e);
        }
        // Step 3: An empty result prints none.
        if (out.isEmpty()) {
            out.add("none");
        }
        return out.toArray(new String[0]);
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        java.util.List<String> all = new java.util.ArrayList<>();
        while (scanner.hasNextLine()) {
            String line = scanner.nextLine().trim();
            if (!line.isEmpty()) {
                all.add(line);
            }
        }
        String[] lines = all.toArray(new String[0]);
        System.out.println(String.join("\n", solve(lines)));
    }
}