Java Utililty Methods JDBC PostgreSQL Connection

String ConnectionString;
Connection PostgreSQLConnection;
Statement stmt;
ConnectionString = "jdbc:postgresql://127.0.0.1:5432/abia/";
try {
    Class.forName("org.postgresql.Driver");
} catch (Exception e) {
    System.out.println(e);
...

return DriverManager.getConnection(DB_CONNECTION_URL, DB_USERNAME, DB_PASSWORD);

String url = "jdbc:postgresql://localhost/marketplace";
Properties props = new Properties();
props.setProperty("user", "marketplace");
props.setProperty("password", "test");
return DriverManager.getConnection(url, props);

Connection con = null;
try {
    Class.forName("org.postgresql.Driver");
    con = DriverManager.getConnection(DB_URL, USERNAME, PASSWORD);
} catch (ClassNotFoundException | SQLException ex) {
    System.out.println(ex.getMessage());
return con;
...

Connection conn = getConnection();
LinkedList<String> list = new LinkedList<String>();
try {
    Statement st = conn.createStatement();
    String sb = "select * from " + tableName;
    ResultSet rs = st.executeQuery(sb);
    while (rs.next()) {
        StringBuilder sql = new StringBuilder();
...

if (connection == null)
    connection = connectToDatabase();
return connection;

List<String> lista = new ArrayList<>();
Connection connection;
try {
    Class.forName(driver);
    connection = (Connection) DriverManager.getConnection(url, user, senha);
    Statement statement = connection.createStatement();
    ResultSet resultSet = statement.executeQuery("SELECT name FROM public.system_database;");
    while (resultSet.next()) {
...

String url = "jdbc:postgresql://192.168.231.10:5432/flexims";
Properties props = new Properties();
props.setProperty("user", "flexims");
props.setProperty("password", "123456");
return DriverManager.getConnection(url, props);

Class.forName("org.postgresql.Driver");
Connection connection = null;
try {
    connection = DriverManager.getConnection("jdbc:postgresql://127.0.0.1:5432/jira", "postgres",
            "Jira733");
} catch (SQLException e) {
    System.out.println("Connection Failed! Check output console");
    e.printStackTrace();
...

try {
    Class.forName("org.postgresql.Driver");
    Connection con = null;
    con = DriverManager.getConnection("jdbc:postgresql://" + host + ":" + port + "/" + nameDB, userDB,
            passwordDB);
    return con;
} catch (Exception e) {
    throw e;
...