[JAVA] for문 Stream 변환 예제 - excel 파일 읽기

Library Info

1. Apache POI

Maven

<!-- https://mvnrepository.com/artifact/org.apache.poi/poi -->

<dependency>

    <groupId>org.apache.poi</groupId>

    <artifactId>poi</artifactId>

    <version>4.1.0</version>

</dependency>

Gradle

// https://mvnrepository.com/artifact/org.apache.poi/poi

compile group: 'org.apache.poi', name: 'poi', version: '4.1.0'

2. Apache POI-ooxml (xlsx파일 사용 시 필요)

Maven

<!-- https://mvnrepository.com/artifact/org.apache.poi/poi-ooxml -->

<dependency>

    <groupId>org.apache.poi</groupId>

    <artifactId>poi-ooxml</artifactId>

    <version>4.1.0</version>

</dependency>

Gradle

// https://mvnrepository.com/artifact/org.apache.poi/poi-ooxml

compile group: 'org.apache.poi', name: 'poi-ooxml', version: '4.1.0'

As-is

public static Map<String, Set<String>> load(String path) {

    if (StringUtils.isEmpty(path)) {

        throw new IllegalArgumentException("학교 목록 파일 경로가 지정되지 않았습니다.");

    }

    Map<String, Set<String>> map = null;

    Set<String> set = null;

    try {

        Workbook workbook = WorkbookFactory.create(new FileInputStream(path));

        int rowindex = 0;

        int columnindex = 0;

        int sheetSize = workbook.getNumberOfSheets();

        map = new HashMap<>();

        Sheet sheet = null;

        Row row = null;

        Cell cell = null;

        for (int i = 0; i < sheetSize; i++) {

            set = new HashSet<>();

            sheet = workbook.getSheetAt(i);

            int rows = sheet.getPhysicalNumberOfRows();

            for (rowindex = 0; rowindex < rows; rowindex++) {

                row = sheet.getRow(rowindex);

                if (row != null) {

                    int cells = row.getPhysicalNumberOfCells();

                    for (columnindex = 0; columnindex <= cells; columnindex++) {

                        cell = row.getCell(columnindex);

                        if (cell == null) {

                            continue;

                        }

                        set.add(Optional.ofNullable(cell.getStringCellValue()).orElse(""));

                    }

                }

            }

            map.put(sheet.getSheetName(), set);

        }

    }catch(Exception e) {

        e.printStackTrace();

    }

    return map;

}

To-be

public static Map<String, Set<String>> load(String path) {

    if (StringUtils.isEmpty(path)) {

        throw new IllegalArgumentException("학교 목록 파일 경로가 지정되지 않았습니다.");

    }

    try {

        Workbook workbook = WorkbookFactory.create(new FileInputStream(path));

        return IntStream.range(0, workbook.getNumberOfSheets())

                .mapToObj(workbook::getSheetAt)

                .collect(

                        Collectors.toMap(

                                Sheet::getSheetName,

                                sheet -> IntStream.range(0, sheet.getPhysicalNumberOfRows())

                                        .mapToObj(sheet::getRow)

                                        .filter(Objects::nonNull)

                                        .map(r -> r.getCell(0))

                                        .filter(Objects::nonNull)

                                        .map(c -> Optional.ofNullable(c.getStringCellValue()).orElse(""))

                                        .collect(Collectors.toSet())

                        )

                );

    }catch(FileNotFoundException fnfe) {

        throw new IllegalArgumentException("학교 목록 파일을 찾을 수 없습니다.");

    } catch (IOException ie) {

        ie.printStackTrace();

        throw new IllegalArgumentException("파일을 읽는 중 오류가 발생하였습니다.");

    }

}