I am using the following code to read in a CSV file:
String next[] = {};
List<String[]> dataArray = new ArrayList<String[]>();
try {
CSVReader reader = new CSVReader(new InputStreamReader(getAssets().open("inputFile.csv")));
for(;;) {
next = reader.readNext();
if(next != null) {
dataArray.add(next);
} else {
break;
}
}
} catch (IOException e) {
e.printStackTrace();
}
This turns a CSV file into the array 'dataArray'. My application is for a dictionary type app - the input data's first column is a list of words, and the second column is the definitions of those words. Here is an example of the array loaded in:
Term 1, Definition 1
Term 2, Definition 2
Term 3, Definition 3
In order to access one of the strings in the array, I use the following code:
dataArray.get(rowNumber)[columnNumber]
However, I need to be able to generate a list of all the terms, so that they can be displayed for the dictionary application. As I understand it, accessing the columns by themselves is a much more lengthy process than accessing the rows (I come from a MATLAB background, where this would be simple).
It seems that in order to have ready access to any row of my input data, I would be better off transposing the data and reading it in that way; i.e.:
Term 1, Term 2, Term3
Definition 1, Definition 2, Definition 3
Of course, I could just provide a CSV file that is transposed in the first place - but Excel or OO Calc don't allow more than 256 rows, and my dictionary contains around 2000 terms.
Any of the following solutions would be welcomed:
A way to transpose an array once it has been read in
An alteration to the code posted above, such that it reads in data in the 'transposed' way
A simple way to read an entire column of an array as a whole
You would probably be better served by using a Map data structure (e.g. HashMap):
String next[] = {};
HashMap<String, String> dataMap = new HashMap<String, String>();
try {
CSVReader reader = new CSVReader(new InputStreamReader(getAssets().open("inputFile.csv")));
for(;;) {
next = reader.readNext();
if(next != null) {
dataMap.put(next[0], next[1]);
} else {
break;
}
}
} catch (IOException e) {
e.printStackTrace();
}
Then you can access the first column by
dataMap.keySet();
and the second column by
dataMap.values();
Note one assumption here: that the first column of your input data is all unique values (that is, there are not repeated values in the "Term" column).
To be able to access the keys (terms) as an array, you can simply do as follows:
String[] terms = new String[dataMap.keySet().size()];
terms = dataMap.keySet().toArray(terms);
If each row has two values, where the first one is the term and the second one is the definition, you could build a Map of it like this (Btw, this while loop does the exact same thing as your for loop):
String next[] = {};
Map<String, String> dataMap = new HashMap<String, String>();
try {
CSVReader reader = new CSVReader(new InputStreamReader(getAssets().open("inputFile.csv")));
while((next = reader.readNext()) != null) {
dataMap.put(next[0], next[1]);
}
} catch (IOException e) {
e.printStackTrace();
}
Then you can get the definition from a term via:
String definition = dataMap.get(term);
or all definitions like this:
for (String term: dataMap.keySet()) {
String definition = dataMap.get(term);
}
Related
I have a csv file 'Master List' with 800 K records, each record have 13 values.
combination of cell[0] and cell[1] give a unique record and I need to update value of cell[12] say status for every record.
I have another csv file say 'Updated subset list'. This is sort of subset of file 'Master list'. For all the records in my 2nd csv which are less in number say 10000, I need to update cell[11] aka status column value of each matching record.
I tried direct BufferedReader, CsvParser from commons-csv and CsvParser from univocity.parsers.
But reading whole file and creating List of 800K is giving out of memory exception.
Same code will be deployed on different servers so I want to have a efficient code for reading huge csv file and updating same file.
Partially reading huge file and writing in same file might corrupt the data.
Any suggestions on how can I do this. ??
File inputF = new File(inputFilePath);
if (inputF.exists()) {
InputStream inputFS = new FileInputStream(inputF);
BufferedReader br = new BufferedReader(new InputStreamReader(inputFS));
// skip the header of the file
String line = br.readLine();
mandatesList = new ArrayList<DdMandates>();
while ((line = br.readLine()) != null) {
mandatesList.add(mapToItem(line));
}
br.close();
}
Memory issue is resolved via doing it in chunks. reading single line and writing single line might result is taking more time. I didn't tried it as my issue was resolved with using batches of 100k records at time and clearing list after writing 100k records
Now issue is updating status is taking too much looping....
I have two csv's. Master sheet (Master list) have 800 K records then I have a subset csv as well say it have 10 k records. This subset csv is updated from some other system and it have updated status say 'OK' and 'NOT OK'. I need to update this status in Master sheet. How can I do that in best possible way. ??? Dumbest way I am using is follwing : –
// Master list have batches but it contains 800 k records and 12 columns
List<DdMandates> mandatesList = new ArrayList<DdMandates>();
// Subset list have updated status
List<DdMandates> updatedMandatesList = new ArrayList<DdMandates>();
// Read Subset csv file and map DdMandates item and then add to updated mandate list
File inputF = new File(Property.inputFilePath);
if(inputF.exists()) {
InputStream inputFS = new FileInputStream(inputF);
BufferedReader br = new BufferedReader(new InputStreamReader(inputFS, "UTF-8"));
checkFilterAndmapToItem(br);
br.close();
In Method checkFilterAndmapToItem(BufferedReader br)
private static void checkFilterAndmapToItem(BufferedReader br) {
FileWriter fileWriter = null;
try {
// skip the header of the csv
String line = br.readLine();
int batchSize = 0, currentBatchNo=0;
fileWriter = new FileWriter(Property.outputFilePath);
//Write the CSV file header
fileWriter.append(FILE_HEADER.toString());
//Add a new line separator after the header
fileWriter.append(NEW_LINE_SEPARATOR);
if( !Property.batchSize.isEmpty()) {
batchSize = Integer.parseInt(Property.batchSize.trim());
}
while ((line = br.readLine()) != null) {
DdMandates item = new DdMandates();
String[] p = line.concat(" ").split(SEPERATOR);
Parse each p[x] and map to item of type DdMandates\
Iterating here on updated mandate list to check if this item is present in updated mandate list
then get that item and update that status to item . so here is a for loop for say 10K elements
mandatesList.add(item);
if (batchSize != 0 && mandatesList.size() == batchSize) {
currentBatchNo++;
logger.info("Batch no. : "+currentBatchNo+" is executing...");
processOutputFile(fileWriter);
mandatesList.clear();
}
}
processing output file here for the last batch ...
}
It will have while loop (800 K iteration) { insider loop 10K iteration for each element )
so at least 800K * 10K loop
Please help in getting its best possible way and reduce iteration .
Thanks in advance
Suppose you are reading 'Main Data File' in batches of 50K:
Store this data in java HashMap using cell[0] and cell[1] as key and rest of the columns as value.
The complexity of get and put is O(1) most of the time. see here
So the complexity for searching 10K records in that particular batch will be O(10K).
HashMap<String, DdMandates> hmap = new HashMap<String, DdMandates>();
Use key=DdMandates.get(0)+DdMandates.get(1)
Note: If 50K records are exceeding the memory limit of HashMap create smaller batches.
For further performance enhancement you can use multi-threading by creating small batches and processing them on different threads.
The first suggestion, when you create the ArrayList, it will make list capacity of 10. So, if you work with large amount of data, initialize it first like:
private static final int LIST_CAPACITY = 800000;
mandatesList = new ArrayList<DdMandates>(LIST_CAPACITY);
The second suggestion, don't store data in the memory, read the data line by line, make your business logic needs, then free up memory, like:
FileInputStream inputStream = null;
Scanner sc = null;
try {
inputStream = new FileInputStream(path);
sc = new Scanner(inputStream, "UTF-8");
while (sc.hasNextLine()) {
String line = sc.nextLine();
/* your business rule here */
}
// note that Scanner suppresses exceptions
if (sc.ioException() != null) {
throw sc.ioException();
}
} finally {
if (inputStream != null) {
inputStream.close();
}
if (sc != null) {
sc.close();
}
}
I am reading two different csv files and populating data into two different objects. I am splitting each line of csv file based on regex(regex is different for two csv files) and populating the object using each data of that array which is obtained by splitting each line using regex as shown below:
public static <T> List<T> readCsv(String filePath, String type) {
List<T> list = new ArrayList<T>();
try {
File file = new File(filePath);
FileInputStream fileInputStream = new FileInputStream(file);
InputStreamReader inputStreamReader = new InputStreamReader(fileInputStream);
BufferedReader bufferedReader = new BufferedReader(inputStreamReader)
list = bufferedReader.lines().skip(1).map(line -> {
T obj = null;
String[] data = null;
if (type.equalsIgnoreCase("Student")) {
data = line.split(",");
ABC abc = new ABC();
abc.setName(data[0]);
abc.setRollNo(data[1]);
abc.setMobileNo(data[2]);
obj = (T)abc;
} else if (type.equalsIgnoreCase("Employee")) {
data = line.split("\\|");
XYZ xyz = new XYZ();s
xyz.setName(Integer.parseInt(data[0]));
xyz.setCity(data[1]);
xyz.setEmployer(data[2]);
xyz.setDesignation(data[3]);
obj = (T)xyz;
}
return obj;
}).collect(Collectors.toList());} catch(Exception e) {
}}
csv files are as below:
i. csv file to populate ABC object:
Name,rollNo,mobileNo
Test1,1000,8888888888
Test2,1001,9999999990
ii. csv file to populate XYZ object
Name|City|Employer|Designation
Test1|City1|Emp1|SSE
Test2|City2|Emp2|
The issue is there can be a missing data for any of the above columns in the csv file as shown in the second csv file. In that case, I will get ArrayIndexOutOfBounds exception.
Can anyone let me know what is the best way to populate the object using the data of the string array?
Thanks in advance.
In addition to the other mistakes you made and that were pointed out to you in the comments your actual problem is caused by line.split("\\|") calling line.split("\\|", 0) which discards the trailing empty String. You need to call it with line.split("\\|", -1) instead and it will work.
The problem appears to be that one or more of the last values on any given CSV line may be empty. In that case, you run into the fact that String.split(String) suppresses trailing empty strings.
Supposing that you can rely on all the fields in fact being present, even if empty, you can simply use the two-arg form of split():
data = line.split(",", -1);
You can find details in that method's API docs.
If you cannot be confident that the fields will be present at all, then you can force them to be by adding delimiters to the end of the input string:
data = (line + ",,").split(",", -1);
Since you only use the first values few values, any extra trailing values introduced by the extra delimiters would be ignored.
I have a csv file. I want to extract particular column from it.For example:
Say, I have csv:
id1,caste1,salary,name1
63,Graham,101153.06,Abraham
103,Joseph,122451.02,Charlie
63,Webster,127965.91,Violet
76,Smith,156150.62,Eric
97,Moreno,55867.74,Mia
65,Reynolds,106918.14,Richard
How can i use opencsv to read only data from header caste1?
Magnilex and Sparky are right in that CSVReader does not support reading values by column name. But that being said there are two ways you can do this.
Given that you have the column names and the default CSVReader reads the header you can search the first the header for the position then use that from there on out;
private int getHeaderLocation(String[] headers, String columnName) {
return Arrays.asList(headers).indexOf(columnName);
}
so your method would look like (leaving out a lot of error checks you will need to put in)
CSVReader reader = new CSVReader(new FileReader("yourfile.csv"));
String [] nextLine;
int columnPosition;
nextLine = reader.readNext();
columnPosition = getHeaderLocation(nextLine, "castle1");
while ((nextLine = reader.readNext()) != null && columnPosition > -1) {
// nextLine[] is an array of values from the line
System.out.println(nextLine[columnPosition]);
}
I would only do the above if you were pressed for time and it was only one column you cared about. That is because openCSV can convert directly to an object that has the variables the same as the header column names using the CsvToBean class and the HeaderColumnNameMappingStrategy.
So first you would define a class that has the fields (and really you only need to put in the fields you want - extras are ignored and missing ones are null or default values).
public class CastleDTO {
private int id1;
private String castle1;
private double salary;
private String name1;
// have all the getters and setters here....
}
Then your code would look like
CSVReader reader = new CSVReader(new FileReader("yourfile.csv"));
HeaderColumnNameMappingStrategy<CastleDTO> castleStrategy = new HeaderColumnNameMappingStrategy<CastleDTO>();
CsvToBean<CastleDTO> csvToBean = new CsvToBean<CastleDTO>();
List<CastleDTO> castleList = csvToBean.parse(castleStrategy, reader);
for (CastleDTO dto : castleList) {
System.out.println(dto.getCastle1());
}
There is no built in functionality in opencsv for reading from a column by name.
The official FAQ example has the following example on how to read from a file:
CSVReader reader = new CSVReader(new FileReader("yourfile.csv"));
String [] nextLine;
while ((nextLine = reader.readNext()) != null) {
// nextLine[] is an array of values from the line
System.out.println(nextLine[0] + nextLine[1] + "etc...");
}
You simply fetch the value in second column for each row by accesing the row with nextLine[1] (remember, arrays indices are zero based).
So, in your case you could simply read from the second line:
CSVReader reader = new CSVReader(new FileReader("yourfile.csv"));
String [] nextLine;
while ((nextLine = reader.readNext()) != null) {
System.out.println(nextLine[1]);
}
For a more sophisticated way of determining the column index from its header, refer to the answer from Scott Conway.
From the opencsv docs:
Starting with version 4.2, there’s another handy way of reading CSV files that doesn’t even require creating special classes. If your CSV file has headers, you can just initialize a CSVReaderHeaderAware and start reading the values out as a map:
reader = new CSVReaderHeaderAware(new FileReader("yourfile.csv"));
record = reader.readMap();
.readMap() will return a single record. You need to call .readMap() repeatedly to get all the records until you get null when it runs to the end (or to the first empty line), e.g.:
Map<String, String> values;
while ((values = reader.readMap()) != null) {
// consume the values here
}
The class also has another constructor which allows more customization, e.g.:
CSVReaderHeaderAware reader = new CSVReaderHeaderAware(
new InputStreamReader(inputStream),
0, // skipLines
parser, // custom parser
false, // keep end of lines
true, // verify reader
0, // multiline limit
null // null for default locale
);
One downside which I have found is that since the reader is lazy it does not offer a record count, therefore, if you need to know the total number (for example to display correct progress information), then you'll need to use another reader just for counting lines.
You also have available the CSVReaderHeaderAwareBuilder
I had a task to remove several columns from existing csv, example of csv:
FirstName, LastName, City, County, Zip
Steve,Hopkins,London,Greater London,15554
James,Bond,Vilnius,Vilniaus,03250
I needed only FirstName and LastName columns with values and it is very important that order should be the same - default rd.readMap() does not preserve the order, code for this task:
String[] COLUMN_NAMES_TO_REMOVE = new String[]{"", "City", "County", "Zip"};
CSVReaderHeaderAware rd = new CSVReaderHeaderAware(new StringReader(old.csv));
CSVWriter writer = new CSVWriter((new FileWriter(new.csv)),
CSVWriter.DEFAULT_SEPARATOR, CSVWriter.NO_QUOTE_CHARACTER, CSVWriter.NO_ESCAPE_CHARACTER, CSVWriter.DEFAULT_LINE_END);
// let's get private field
Field privateField = CSVReaderHeaderAware.class.getDeclaredField("headerIndex");
privateField.setAccessible(true);
Map<String, Integer> headerIndex = (Map<String, Integer>) privateField.get(rd);
// do ordering in natural order - 0, 1, 2 ... n
Map<String, Integer> sortedInNaturalOrder = headerIndex.entrySet().stream()
.sorted(Map.Entry.comparingByValue(Comparator.naturalOrder()))
.collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue,
(oldValue, newValue) -> oldValue, LinkedHashMap::new));
// let's get headers in natural order
List<String> headers = sortedInNaturalOrder.keySet().stream().distinct().collect(Collectors.toList());
// let's remove headers
List<String> removedColumns = new ArrayList<String>(Arrays.asList(COLUMN_NAMES_TO_REMOVE));
headers.removeAll(removedColumns);
// save column names
writer.writeNext(headers.toArray(new String[headers.size()]));
List<String> keys = new ArrayList<>();
Map<String, String> values;
while ((values = rd.readMap()) != null) {
for (String key : headers) {
keys.add(values.get(key));
if (keys.size() == headers.size()) {
String[] itemsArray = new String[headers.size()];
itemsArray = keys.toArray(itemsArray);
// save values
writer.writeNext(itemsArray);
keys.clear();
}
}
}
writer.flush();
Output:
FirstName, LastName
Steve,Hopkins
James,Bond
Looking at the javadoc
if you create a CSVReader object, then you can use the method .readAll to pull the entire file. It returns a List of String[], with each String[] representing a line of the file. So now you have the tokens of each line, and you only want the second element of that, so split them up as they have been nicely given to you with delimiters. And on each line you only want the second element, so:
public static void main(String[] args){
String data = "63,Graham,101153.06,Abraham";
String result[] = data.split(",");
System.out.print(result[1]);
}
I think i found a bug. Or maybe it isn't, but Super CSV can't handle that well.
I'm parsing a CSV file with 41 Columns with a MapReader. However, i'm getting that CSV - and the Webservice that gives me the CSV messes up one line. The "headline" line is a tab-delimited Row with 41 Cells.
And the "wrong line" is a tab-delimited Row with 36 Cells and the content doesn't make any sense.
This is the code i'm using:
InputStream fis = new FileInputStream(pathToCsv);
InputStreamReader inReader = new InputStreamReader(fis, "ISO-8859-1");
ICsvMapReader mapReader = new CsvMapReader(inReader, new CsvPreference.Builder('"','\t',"\r\n").build());
final String[] headers = mapReader.getHeader(true);
Map<String, String> row;
while( (row = mapReader.read(headers)) != null ) {
// do something
}
I get an exception when executing mapReader.read(headers) in the row i mentioned above. This is the exception:
org.supercsv.exception.SuperCsvException:
the nameMapping array and the sourceList should be the same size (nameMapping length = 41, sourceList size = 36)
context=null
at org.supercsv.util.Util.filterListToMap(Util.java:121)
at org.supercsv.io.CsvMapReader.read(CsvMapReader.java:79)
at test.MyClass.readCSV(MyClass.java:20)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
What do you think i should do ?
I don't want the whole application to crash, just because one row is messed up, i'd rather skip that row.
This is a good question! As a Super CSV developer, I'll look into creating some exception handling examples on the website.
You could keep it simple and use CsvListReader (which doesn't care how many columns there are), and then just create the Map yourself:
public class HandlingExceptions {
private static final String INPUT =
"name\tage\nTom\t25\nAlice\nJim\t44\nMary\t33\tInvalid";
public static void main(String[] args) throws IOException {
// use CsvListReader (can't be sure there's the correct no. of columns)
ICsvListReader listReader = new CsvListReader(new StringReader(INPUT),
new CsvPreference.Builder('"', '\t', "\r\n").build());
final String[] headers = listReader.getHeader(true);
List<String> row = null;
while ((row = listReader.read()) != null) {
if (listReader.length() != headers.length) {
// skip row with invalid number of columns
System.out.println("skipping invalid row: " + row);
continue;
}
// safe to create map now
Map<String, String> rowMap = new HashMap<String, String>();
Util.filterListToMap(rowMap, headers, row);
// do something with your map
System.out.println(rowMap);
}
listReader.close();
}
}
Output:
{name=Tom, age=25}
skipping invalid row: [Alice]
{name=Jim, age=44}
skipping invalid row: [Mary, 33, Invalid]
If you were concerned with using Super CSV's Util class (it's possible it could change - it's really an internal utility class), you could combine 2 readers as I've suggested here.
You could try catching SuperCsvException, but you might end up suppressing more than just an invalid number of columns. The only Super CSV exception I'd recommend catching (though not applicable in your situation as you're not using cell processors) is SuperCsvConstraintViolationException, as it's indicates the file is in the correct format, but the data doesn't satisfy your expected constraints.
You have to ask yourself what have to be done if the CSV file contains data which cannot be parsed. How critical would it be to skip those lines. In one scenario it could be ok to just drop it in other scenarios it might be better to stop the whole process and tell the user to fix the file first.
I am sure you can build both scenarios with Super CSV. You definitely have to handle that Exception and react appropriate to the mentioned scenarios.
Well, i came up with some solution, but i don't think it's optimal.
while (true) {
try {
if ((row = mapReader.read(headers)) == null) {
break;
} else {
// do something
}
} catch (SuperCsvException ex) {
continue;
}
}
UPDATE
Changed Exception with SuperCsvException
I'm reading 2 csv files: store_inventory & new_acquisitions.
I want to be able to compare the store_inventory csv file with new_acquisitions.
1) If the item names match just update the quantity in store_inventory.
2) If new_acquisitions has a new item that does not exist in store_inventory, then add it to the store_inventory.
Here is what i have done so far but its not very good. I added comments where i need to add taks 1 & 2.
Any advice or code to do the above tasks would be great! thanks.
File new_acq = new File("/src/test/new_acquisitions.csv");
Scanner acq_scan = null;
try {
acq_scan = new Scanner(new_acq);
} catch (FileNotFoundException ex) {
Logger.getLogger(mainpage.class.getName()).log(Level.SEVERE, null, ex);
}
String itemName;
int quantity;
Double cost;
Double price;
File store_inv = new File("/src/test/store_inventory.csv");
Scanner invscan = null;
try {
invscan = new Scanner(store_inv);
} catch (FileNotFoundException ex) {
Logger.getLogger(mainpage.class.getName()).log(Level.SEVERE, null, ex);
}
String itemNameInv;
int quantityInv;
Double costInv;
Double priceInv;
while (acq_scan.hasNext()) {
String line = acq_scan.nextLine();
if (line.charAt(0) == '#') {
continue;
}
String[] split = line.split(",");
itemName = split[0];
quantity = Integer.parseInt(split[1]);
cost = Double.parseDouble(split[2]);
price = Double.parseDouble(split[3]);
while(invscan.hasNext()) {
String line2 = invscan.nextLine();
if (line2.charAt(0) == '#') {
continue;
}
String[] split2 = line2.split(",");
itemNameInv = split2[0];
quantityInv = Integer.parseInt(split2[1]);
costInv = Double.parseDouble(split2[2]);
priceInv = Double.parseDouble(split2[3]);
if(itemName == itemNameInv) {
//update quantity
}
}
//add new entry into csv file
}
Thanks again for any help. =]
Suggest you use one of the existing CSV parser such as Commons CSV or Super CSV instead of reinventing the wheel. Should make your life a lot easier.
Your implementation makes the common mistake of breaking the line on commas by using line.split(","). This does not work because the values themselves might have commas in them. If that happens, the value must be quoted, and you need to ignore commas within the quotes. The split method can not do this -- I see this mistake a lot.
Here is the source of an implementation that does it correctly:
http://agiletribe.purplehillsbooks.com/2012/11/23/the-only-class-you-need-for-csv-files/
With help of the open source library uniVocity-parsers, you could develop with pretty clean code as following:
private void processInventory() throws IOException {
/**
* ---------------------------------------------
* Read CSV rows into list of beans you defined
* ---------------------------------------------
*/
// 1st, config the CSV reader with row processor attaching the bean definition
CsvParserSettings settings = new CsvParserSettings();
settings.getFormat().setLineSeparator("\n");
BeanListProcessor<Inventory> rowProcessor = new BeanListProcessor<Inventory>(Inventory.class);
settings.setRowProcessor(rowProcessor);
settings.setHeaderExtractionEnabled(true);
// 2nd, parse all rows from the CSV file into the list of beans you defined
CsvParser parser = new CsvParser(settings);
parser.parse(new FileReader("/src/test/store_inventory.csv"));
List<Inventory> storeInvList = rowProcessor.getBeans();
Iterator<Inventory> storeInvIterator = storeInvList.iterator();
parser.parse(new FileReader("/src/test/new_acquisitions.csv"));
List<Inventory> newAcqList = rowProcessor.getBeans();
Iterator<Inventory> newAcqIterator = newAcqList.iterator();
// 3rd, process the beans with business logic
while (newAcqIterator.hasNext()) {
Inventory newAcq = newAcqIterator.next();
boolean isItemIncluded = false;
while (storeInvIterator.hasNext()) {
Inventory storeInv = storeInvIterator.next();
// 1) If the item names match just update the quantity in store_inventory
if (storeInv.getItemName().equalsIgnoreCase(newAcq.getItemName())) {
storeInv.setQuantity(newAcq.getQuantity());
isItemIncluded = true;
}
}
// 2) If new_acquisitions has a new item that does not exist in store_inventory,
// then add it to the store_inventory.
if (!isItemIncluded) {
storeInvList.add(newAcq);
}
}
}
Just follow this code sample I worked out according to your requirements. Note that the library provided simplified API and significent performance for parsing CSV files.
The operation you are performing will require that for each item in your new acquisitions, you will need to search each item in inventory for a match. This is not only not efficient, but the scanner that you have set up for your inventory file would need to be reset after each item.
I would suggest that you add your new acquisitions and your inventory to collections and then iterate over your new acquisitions and look up the new item in your inventory collection. If the item exists, update the item. If it doesnt, add it to the inventory collection. For this activity, it might be good to write a simple class to contain an inventory item. It could be used for both the new acquisitions and for the inventory. For a fast lookup, I would suggest that you use HashSet or HashMap for your inventory collection.
At the end of the process, dont forget to persist the changes to your inventory file.
As Java doesn’t support parsing of CSV files natively, we have to rely on third party library. Opencsv is one of the best library available for this purpose. It’s open source and is shipped with Apache 2.0 licence which makes it possible for commercial use.
Here, this link should help you and others in the situations!
For writing to CSV
public void writeCSV() {
// Delimiter used in CSV file
private static final String NEW_LINE_SEPARATOR = "\n";
// CSV file header
private static final Object[] FILE_HEADER = { "Empoyee Name","Empoyee Code", "In Time", "Out Time", "Duration", "Is Working Day" };
String fileName = "fileName.csv");
List<Objects> objects = new ArrayList<Objects>();
FileWriter fileWriter = null;
CSVPrinter csvFilePrinter = null;
// Create the CSVFormat object with "\n" as a record delimiter
CSVFormat csvFileFormat = CSVFormat.DEFAULT.withRecordSeparator(NEW_LINE_SEPARATOR);
try {
fileWriter = new FileWriter(fileName);
csvFilePrinter = new CSVPrinter(fileWriter, csvFileFormat);
csvFilePrinter.printRecord(FILE_HEADER);
// Write a new student object list to the CSV file
for (Object object : objects) {
List<String> record = new ArrayList<String>();
record.add(object.getValue1().toString());
record.add(object.getValue2().toString());
record.add(object.getValue3().toString());
csvFilePrinter.printRecord(record);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
fileWriter.flush();
fileWriter.close();
csvFilePrinter.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
You can use Apache Commons CSV api.
FYI this anwser : https://stackoverflow.com/a/42198895/6549532
Read / Write Example