如何从CSV文件获取特定数据

Question

I have a very big CSV file, I have managed to put all this into an ArrayList using Scanner

    Path filepath = Paths.get("./data.csv");

    try{
      Scanner InputStream = new Scanner(filepath);
      while (InputStream.hasNext()){

        wholefile.add(String.valueOf(InputStream.next()));
      } InputStream.close();

    System.out.println(wholefile);

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

  }

and my array looks like this :

wholefile = [id,property, address,first_name,last_name,email,Owner, contact, address,Price,Date, sold, 1,94032, Mockingbird, Alley,Brander,Verillo,bverillo0@sogou.com,,435587.57,, 2,293, Haas, Lane,Maxy,Reynalds...........]

Here is a screenshot of the csv file in excel https://plus.google.com/photos/photo/115135191238195349859/6559552907258825106?authkey=CIu-hovf5pj29gE

There are some things that I would like to do with this data but I am confused what methods I need to write:

1. Get a property record by ID
2. Get a list of n number of top priced properties
3. Total sales for a month.

any help or guidance would be much appreciated, I'm not sure if I'm goign about this the right way

https://plus.google.com/photos/photo/115135191238195349859/6559637333893665186

Answer 1

Don't waste time by reinventing the wheel .

I suggest to use Apache Commons CSV library to manipulate .csv files.

you can find official doc here .

And some examples here .

Answer 2

With an ArrayList of Strings will have a bad Performance at time of doing what do you want. First Create an Object that Match your CVS Header. Then at time of reading the File start adding to an ArrayList of the Object you created, and for sorting, search and a Total sales just make a stream over the ArrayList.

Answer 3

I had to roll out a custom CSV parser for some proof of concept we were trying to do and I think you could re purpose it here:

CSVReader.java

public class CSVReader implements Iterable<CSVRow> {

    private List<String> _data;
    private int _itPos = 0;
    private int _skip = 0;
    private FileIterator _it;
    private boolean _hasTrailingComma = false;

    public CSVReader(Path path, boolean hasTrailingComma) throws IOException {
        this(Files.readAllLines(path), hasTrailingComma);
    }

    public CSVReader(Path path) throws IOException {
        this(path, false);
    }

    public CSVReader(List<String> data, boolean hasTrailingComma) {
        _data = data;
        _it = new FileIterator();
        _hasTrailingComma = hasTrailingComma;
    }

    public CSVReader(List<String> data) {
        this(data, false);
    }

    public CSVRow getHeaders() {
        return new CSVRow(_data.get(0), _hasTrailingComma);
    }

    public void skip(int rows) {
        _skip = rows;
    }

    @Override
    public Iterator<CSVRow> iterator() {
        _itPos = _skip;
        return _it;
    }

    private class FileIterator implements Iterator<CSVRow> {

        @Override
        public boolean hasNext() {
            return _itPos < _data.size();
        }

        @Override
        public CSVRow next() {
            if (_itPos == _data.size()) {
                throw new NoSuchElementException();
            }
            return new CSVRow(_data.get(_itPos++), _hasTrailingComma);
        }

    }
}

CSVRow.java

public class CSVRow implements Iterable<String> {

    private String[] _data;
    private int _itPos = 0;
    private int _skip = 0;
    private RowIterator _it = null;
    private int _actualLength = 0;

    public CSVRow(String row, boolean trailingComma) {
        // Minor hack
        // in case the data doesn't end in commas
        // we check for the last character and add
        // a comma. Ideally, the input file should be fixed;
        if(trailingComma && !row.endsWith(",")) {
            row += ",";
        }
        _data = row.split("\\s*,\\s*", -1);
        _actualLength = trailingComma ? _data.length - 1 : _data.length;
        _it = new RowIterator();
    }

    public CSVRow(String row) {
        this(row, false);
    }

    public void skip(int cells) {
        _skip = cells;
    }

    @Override
    public Iterator<String> iterator() {
        _itPos = _skip;
        return _it;
    }

    public String[] toArray() {
        return Arrays.copyOf(_data, _actualLength);
    }

    private class RowIterator implements Iterator<String> {

        @Override
        public boolean hasNext() {
            return _itPos < _actualLength;
        }

        @Override
        public String next() {
            if (_itPos == _actualLength) {
                throw new NoSuchElementException();
            }
            return _data[_itPos++];
        }

    }
}

Usage

public static void main(String[] args) {
    Path filepath = Paths.get("./data.csv");
    CSVReader reader = new CSVReader(filepath);
    for (CSVRow row : reader) {
        for (String str : row) {
                System.out.printf("%s ", str);
        }
        System.out.println();
    }
}

Now it will be useful to model each row as an object so that you can do stuff with it in Java. You can define a class Property that models each row

public class Property {

    private int id;
    private String address;
    private String firstName;
    private String lastName;
    private String email;
    private String ownerContactAddress;
    private BigDecimal price;
    private java.sql.Date dateSold;

    public Property() {
    } 

    // Setters and getters
    public long getId() {
        return this.id;
    }
    public void setId(String id) {
        this.id = Long.parseLong(id);
    }
    public String getAddress() {
        return this.address;
    }
    public void setAddress(String address) {
        this.address = address;
    }
    // TODO: setter/getters for firstName, lastName, email, ownerContactAddress

    public BigDecimal getPrice() {
        return this.price;
    }
    public void setPrice(String price, Locale locale) throws ParseException {
        NumberFormat format = NumberFormat.getNumberInstance(locale);
        if (format instanceof DecimalFormat) {
            ((DecimalFormat) format).setParseBigDecimal(true);
        }
        this.price = (BigDecimal) format.parse(amount.replaceAll("[^\\d.,]",""));
    }
    public java.sql.Date getDateSold() {
        return this.dateSold;
    }
    public void setDateSold(String date, String format) throws ParseException {
        SimpleDateFormat sdf = new SimpleDateFormat(format);
        this.dateSold = new Date(sdf.parse(date).getTime());
    }
}

Bringing everything together (Not tested)

public static void main(String[] args) {

    // Collection to store properties
    // You could also write a class to wrap this 
    // map along with the methods you need to implement
    // Say PropertyTable {
    //        private Map<Long, Property> properties ...
    //        Property getPropertyById(long id);
    //        getHighestPriced() // sort the map by price
    // }
    Map<Long, Property> properties = new HashMap<>();

    Path filepath = Paths.get("./data.csv");
    CSVReader reader = new CSVReader(filepath);
    for (CSVRow row : reader) {
        Iterator<String> it = row.iterator();
        Property p = new Property();
        p.setId(it.next());
        p.setAddress(it.next());
        // ... set the remaining properties
        p.setPrice(it.next(), new Locale("en", "GB"));
        p.seDateSold(it.next(), "MM/dd/yyyy");
        properties.put(p.getId(), p);
    }
    // At this point, you should have all the properties read

    // let's try to get property with id 5
    Property prop = properties.get(5L);
}

I hope this helps.