DatabaseConnection.java

public class DatabaseConnection {
 private static DatabaseConnection instance;
 
 private DatabaseConnection() {
 System.out.println("Database Connection established");
 }

 public static DatabaseConnection getInstance() {
 if (instance == null) {
 instance = new DatabaseConnection();
 }
 return instance;
 }

 public void query(String sql) {
 System.out.println("Executing query: " + sql);
 }

 public static void main(String[] args) {
 DatabaseConnection db1 = DatabaseConnection.getInstance();
 DatabaseConnection db2 = DatabaseConnection.getInstance();
 
 db1.query("SELECT * FROM users");
 db2.query("INSERT INTO users VALUES (1, 'John')");
 
 System.out.println(db1 == db2);
 }
}