@Testvoid testStringJoinerMethod(){    String[] fields = { "name", "position", "salary" };    String table = "employee";    String select = buildSelectSql(table, fields);    System.out.println(select);    System.out.println("SELECT name, position, salary FROM employee".equals(select) ? "测试成功" : "测试失败");}

private String buildSelectSql(String table, String[] fields) {    StringJoiner sj = new StringJoiner(", ","SELECT "," FROM "+ table);    for (String field : fields) {        sj.add(field);    }    return sj.toString();}