java - 从另一个迭代和另一个类添加到 HashSet

Question

我正在使用 Apache POI 使用电子表格第 1 工作表中的 3 个值填充 HashSet。由于我还需要访问电子表格的第 2 个表以获取另一个值，因此我再次迭代它:

public class Students {

private int numStudents;
HashSet<Student> studentsRoster1 = new HashSet<Student>();
HashSet<Student> studentsRoster;

public Students(String studentsDb) {

    try {
        FileInputStream file = new FileInputStream(new File(studentsDb));

        XSSFWorkbook workbook = new XSSFWorkbook(file);

        DataFormatter fmt = new DataFormatter();

        // Get first sheet from the workbook
        XSSFSheet sheet = workbook.getSheetAt(0);

        String name = null;
        String email = null;
        int id1 = 0;
        String id = null;

        Iterator<Row> rowIterator = sheet.iterator();
        while (rowIterator.hasNext()) {
            Student student = new Student();

            Row row = rowIterator.next();
            // Skip the first row
            if (row.getRowNum() == 0) {
                continue;
            }

            Iterator<Cell> cellIterator = row.cellIterator();

            while (cellIterator.hasNext()) {

                Cell cell = cellIterator.next();

                Cell cell0 = row.getCell(0);
                Cell cell1 = row.getCell(1);
                String formatValue = fmt.formatCellValue(cell1);
                Cell cell2 = row.getCell(2);

                name = cell0.getStringCellValue();
                id1 = (int) cell1.getNumericCellValue();
                email = cell2.getStringCellValue();

                id = String.valueOf(id1);

                student.setName(name);
                student.setid(id);
                student.setEmail(email);

                studentsRoster1.add(student);
            }
        }

    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

    /**** access second sheet for team info ****/
    try {
        FileInputStream file = new FileInputStream(new File(studentsDb));

        XSSFWorkbook workbook = new XSSFWorkbook(file);

        // Get second sheet from the workbook
        XSSFSheet sheet = workbook.getSheetAt(1);

        String team = null;

        Iterator<Row> rowIterator = sheet.iterator();
        while (rowIterator.hasNext()) {
            Student student = new Student();

            Row row = rowIterator.next();
            // Skip the first row
            if (row.getRowNum() == 0) {
                continue;
            }

            Iterator<Cell> cellIterator = row.cellIterator();

            while (cellIterator.hasNext()) {

                Cell cell = cellIterator.next();

                Cell cell0 = row.getCell(0);

                team = cell0.getStringCellValue();

                student.setTeam(team);
            }
        }

    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

    this.studentsRoster = studentsRoster1;
}
public HashSet<Student> getStudents() {
    return studentsRoster;
}
}

如您所见，我正在创建 HashSet StudentsRoster1；但最终，我需要归还学生名册。我还没有找到将第四个值 student.setTeam(team); 正确添加到 HashSet 的方法。我想创建另一个 HashSet 并使用 union 吗？

我还需要从另一个类添加到 StudentsRoster HashSet，该类正在迭代另一个电子表格以添加另一个值 student.setXXX(xxx);。

我也做不到。

非常感谢任何建议。

Answer 1

您可以在一个循环中完成此操作，如下所示:

private static final int NAME_INDEX = 0;
private static final int ID_INDEX = 1;
private static final int EMAIL_INDEX = 2;
private static final int TEAM_INDEX = 0;

private int numStudents;
HashSet<Student> studentsRoster = new HashSet<Student>();


public Students(String studentsDb) {
    try {
        HashSet<Student> newStudentsRoster = new HashSet<Student>();
        FileInputStream file = new FileInputStream(new File(studentsDb));

        XSSFWorkbook workbook = new XSSFWorkbook(file);

        // Get first sheet from the workbook
        XSSFSheet sheet0 = workbook.getSheetAt(0);

        // Get second sheet from the workbook
        XSSFSheet sheet1 = workbook.getSheetAt(1);

        Iterator<Row> rowIterator0 = sheet0.iterator();
        Iterator<Row> rowIterator1 = sheet1.iterator();
        while (rowIterator0.hasNext() && rowIterator1.hasNext()) {
            Row row0 = rowIterator0.next();
            Row row1 = rowIterator1.next();
            // Skip the first row
            if (row0.getRowNum() > 0) {
                Student student = new Student();
                Iterator<Cell> cellIterator0 = row0.cellIterator();
                Iterator<Cell> cellIterator1 = row1.cellIterator();
                if (cellIterator0.hasNext()) {
                    student.setName(row0.getCell(NAME_INDEX).getStringCellValue());
                    Integer id = row0.getCell(ID_INDEX).getNumericCellValue();
                    if (id != null){               
                        student.setId(id.toString());
                    }
                    student.setEmail(row0.getCell(EMAIL_INDEX).getStringCellValue());
                }
                if (cellIterator1.hasNext()) {
                    student.setTeam(row1.getCell(TEAM_INDEX).getStringCellValue());
                }
                newStudentsRoster.add(student);
            }
        }
        numStudents = newStudentsRoster.size();
        studentsRoster = newStudentsRoster;
    } catch (FileNotFoundException e) {
        e.printStackTrace(); // <- this hides the errors, you must avoid it
    } catch (IOException e) {
        e.printStackTrace(); // <- this hides the errors, you must avoid it
    }
}