Update MoleculeDatabase.java

 */

public class MoleculeDatabase implements Serializable {

    public ArrayList<MoleculeDatabase> db;   // Molecule database

    public ArrayList<ArrayList<Molecule>> db;   // Molecule database

    /**

     * Constructs a database

     * Find isomorphic molecule from the database

     */

    public Molecule findMolecule(Molecule molecule) {

        // Iterate through the array list of molecules inside the database

        for (Molecule dbMolecule : db) {

        // Retrieve the partitioned array list based on the number of atoms

        int numAtoms = molecule.getNumAtoms();

        ArrayList<Molecule> moleculesWithSameNumAtoms = db.get(numAtoms);

        // Iterate through the array list of molecules with the same number of atoms

        for (Molecule dbMolecule : moleculesWithSameNumAtoms) {

            Molecule result = dbMolecule.areMoleculesEqual(molecule);

            if (result != null) {

                return result; // Return the isomorphic molecule

            }

        }

        System.out.println("No isomorphic molecule found in database.");

        return null; // Return null if molecule not found

    }