use h2 database.

pom.xml

@@ -46,5 +46,12 @@
 			<version>5.5.2</version>
 			<scope>test</scope>
 		</dependency>
+		<!-- https://mvnrepository.com/artifact/com.h2database/h2 -->
+		<dependency>
+		    <groupId>com.h2database</groupId>
+		    <artifactId>h2</artifactId>
+		    <version>2.2.224</version>
+		</dependency>
+
 	</dependencies>
 </project>

src/main/java/lab/ScoreDAO.java

@@ -16,6 +16,20 @@ import java.util.stream.Collectors;
 
 public class ScoreDAO {
 
+	@SuppressWarnings("unused")
+	private static final String SQL_CREATE_DERBY = "CREATE TABLE score ("
+				+ "id INT NOT NULL GENERATED ALWAYS AS IDENTITY, "
+				+ "score_value INT NOT NULL, "
+				+ "name VARCHAR(255) NOT NULL, "
+				+ "PRIMARY KEY (id)"
+				+ ")";
+
+	private static final String SQL_CREATE_H2 = "CREATE TABLE IF NOT EXISTS score ("
+			+ "  id INT AUTO_INCREMENT PRIMARY KEY,"
+			+ "  score_value INT NOT NULL,"
+			+ "  name VARCHAR(255) NOT NULL"
+			+ ")"	;
+	
 	public ScoreDAO() {
 		
 		try (Connection conn = getConnection()) {
@@ -28,7 +42,7 @@ public class ScoreDAO {
 	public List<Score> load( ){
 		List<Score> result = new LinkedList<>();
 		try(Connection con = getConnection(); Statement stmt = con.createStatement()) {
-			try(ResultSet rs = stmt.executeQuery("SELECT id, value, name FROM score")) {
+			try(ResultSet rs = stmt.executeQuery("SELECT id, score_value, name FROM score")) {
 				while (rs.next()) {
 					result.add(new Score(rs.getInt(1), rs.getInt(2), rs.getString(3)));
 				}
@@ -41,13 +55,6 @@ public class ScoreDAO {
 	
 	public void save(List<Score> scores) {
 		
-		/*Set<Integer> m = new HashSet<>();
-		for (Score score: scores) {
-			if (score.getId() == null) {
-				continue;
-			}
-			m.add(score.getId());
-		}*/
 		Set<Integer> m = scores.stream()
 							   .filter(s -> s.getId() != null)
 							   .map(Score::getId)
@@ -58,7 +65,7 @@ public class ScoreDAO {
 		removeByIDS(idsOnlyInDB);
 		List<Score> scoreSaved = new LinkedList<>();
 		try (Connection con = getConnection(); 
-			 PreparedStatement pstmt = con.prepareStatement("INSERT INTO score (value, name) VALUES (?, ?)"
+			 PreparedStatement pstmt = con.prepareStatement("INSERT INTO score (score_value, name) VALUES (?, ?)"
 					                                        , Statement.RETURN_GENERATED_KEYS)) {
 			for (Score score: scores) {
 				if (score.getId() != null) {
@@ -78,7 +85,7 @@ public class ScoreDAO {
 					score.setId(rs.getInt(1));
 				}
 			}
-			
+			return;
 		} catch (SQLException e) {
 			e.printStackTrace();
 		}
@@ -101,12 +108,7 @@ public class ScoreDAO {
 
 	private void createTable(Connection conn) {
 		try  (Statement stmt = conn.createStatement()){
-			stmt.execute("CREATE TABLE score ("
-						+ "id INT NOT NULL GENERATED ALWAYS AS IDENTITY, "
-						+ "value INT NOT NULL, "
-						+ "name VARCHAR(255) NOT NULL, "
-						+ "PRIMARY KEY (id)"
-						+ ")");
+			stmt.execute(SQL_CREATE_H2);
 		} catch (SQLException e) {
 			if (e.getSQLState().equals("X0Y32")) {
 				//ignore this because table exists
@@ -119,7 +121,7 @@ public class ScoreDAO {
 
 	private Connection getConnection() {
 		try {
-			return DriverManager.getConnection("jdbc:derby:scoreDB;create=true");
+			return DriverManager.getConnection("jdbc:h2:./scoreDBh2");
 		} catch (SQLException e) {
 			e.printStackTrace();
 			return null;