### Question:
TableDatabaseNameJoiner { public static String dotJoin(String x, String y) { return String.join(".", x, y); } private  TableDatabaseNameJoiner(); static String dotJoin(String x, String y);  }### Answer:
@Test public void typical() { String databaseName = "database"; String tableName = "table"; assertThat(TableDatabaseNameJoiner.dotJoin(databaseName, tableName)).isEqualTo("database.table"); }
@Test public void nullInput() { String databaseName = "database"; String tableName = null; assertThat(TableDatabaseNameJoiner.dotJoin(databaseName, tableName)).isEqualTo("database.null"); }
@Test public void blankInput() { String databaseName = "database"; String tableName = ""; assertThat(TableDatabaseNameJoiner.dotJoin(databaseName, tableName)).isEqualTo("database."); }