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How to deal with NumberFormatException when reading from a csv file [duplicate]

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How can I prevent java.lang.NumberFormatException: For input string: "N/A"?
(6 answers)
Closed 9 months ago.
My task is to read values from a csv file, and import each line of information from this file into an object array. I think my issue is the blank data elements in my csv file which doesn't work for my parsing from string to int, but I have found no way to deal with this. Here is my code:
`fileStream = new FileInputStream(pFileName);
rdr = new InputStreamReader(fileStream);
bufRdr = new BufferedReader(rdr);
lineNum = 0;`
while (line != null) {
lineNum++;
String[] Values = new String[13];
Values = line.split(",");
int cumulPos = Integer.parseInt(Values[6]);
int cumulDec = Integer.parseInt(Values[7]);
int cumuRec = Integer.parseInt(Values[8]);
int curPos = Integer.parseInt(Values[9]);
int hosp = Integer.parseInt(Values[10]);
int intenCar = Integer.parseInt(Values[11]);
double latitude = Double.parseDouble(Values[4]);
double longitude = Double.parseDouble(Values[5]);
covidrecordArray[lineNum] = new CovidRecord(Values[0], cumulPos, cumulDec, cumuRec, curPos, hosp,
intenCar, new Country(Values[1], Values[2], Values[3], Values[13], latitude, longitude));
If anyone could help it would be greatly appreciated.

As already suggested, use a proper CSV Parser if you can but if for some unknown reason you can't, this could be one way you can do it. Be sure to read the comments in code:
fileStream = new FileInputStream(pFileName);
rdr = new InputStreamReader(fileStream);
bufRdr = new BufferedReader(rdr);
// Remove the following line if there is no Header line in the CSV file.
String line = bufRdr.readLine();
String csvFileDataDelimiter = ",";
List<CovidRecord> recordsList = new ArrayList<>();
// True value calculated later in code (read comments).
int expectedNumberOfElements = 0; // 0 is default
while ((line = bufRdr.readLine()) != null) {
line = line.trim();
// If for some crazy reason a blank line is encountered...skip it.
if (line.isEmpty()) {
continue;
}
/* Get the expected number of elements within each CSV File Data Line.
This is based off of the number of actual delimiters within a file
data line plus 1. This is only calculated from the very first data
line. */
if (expectedNumberOfElements == 0) {
expectedNumberOfElements = line.replaceAll("[^\\" + csvFileDataDelimiter + "]", "").length() + 1;
}
/* Create and fill (with Null String) an array to be the expected
size of a CSV data line. This is done because if a data line
contains nothing for the last data element on that line then
when the line is split, the srray that is created will be short
by one element. This will ensure that there will alsways be a
Null String ("") present within the array when there is nothing
in the CSV data line. This null string is used in data validations
so as to provide a default value (like 0) if an Array Element
contains an actual Null String (""). */
String[] csvLineElements = new String[expectedNumberOfElements];
Arrays.fill(csvLineElements, "");
/* Take the array from the split (values) and place the data into
the csvLineElements[] array. */
String[] values = line.split("\\s*,\\s*"); // Takes care of any comma/whitespace combinations (if any).
for (int i = 0; i < values.length; i++) {
csvLineElements[i] = values[i];
}
/* Is the csvLineElements[] element a String representation of a signed
or unsigned integer data type value ("-?\\d+"). If so, convert the
String array element into an Integer value. If not, provide a default
value of 0. */
int cumulPos = Integer.parseInt(csvLineElements[6].matches("-?\\d+") ? csvLineElements[6] : "0");
int cumulDec = Integer.parseInt(csvLineElements[7].matches("-?\\d+") ? csvLineElements[7] : "0");
int cumuRec = Integer.parseInt(csvLineElements[8].matches("-?\\d+") ? csvLineElements[8] : "0");
int curPos = Integer.parseInt(csvLineElements[9].matches("-?\\d+") ? csvLineElements[9] : "0");
int hosp = Integer.parseInt(csvLineElements[10].matches("-?\\d+") ? csvLineElements[10] : "0");
int intenCar = Integer.parseInt(csvLineElements[11].matches("-?\\d+") ? csvLineElements[11] : "0");
/* Is the csvLineElements[] element a String representation of a signed
or unsigned integer or floating point value ("-?\\d+(\\.\\d+)?").
If so, convert the String array element into an Double data type value.
If not, provide a default value of 0.0 */
double latitude = Double.parseDouble(csvLineElements[4]
.matches("-?\\d+(\\.\\d+)?") ? csvLineElements[4] : "0.0d");
double longitude = Double.parseDouble(csvLineElements[5]
.matches("-?\\d+(\\.\\d+)?") ? csvLineElements[5] : "0.0d");
/* Create an instance of Country to pass into the constructor of
CovidRecord below. */
Country country = new Country(csvLineElements[1], csvLineElements[2],
csvLineElements[3], csvLineElements[13],
latitude, longitude);
// Create an add an instance of CovidRecord to the recordsList List.
recordsList.add(new CovidRecord(csvLineElements[0], cumulPos, cumulDec,
cumuRec, curPos, hosp, intenCar, country));
// Do what you want with the recordList List....
}
For obvious reasons, the code above was not tested. If you have any problems with it then let me know.
You will also notice the instead of the covidrecordArray[] CovidRecord Array I opted to use a List Interface named recordsList. This List can grow dynamically whereas the array is fixed meaning you need to determine the number of data lines within the file when initializing the array. This is not required with the List.

you can create one generic method for null check and check if it's null then return empty string or any thing else based on your needs
int hosp = Integer.parseInt(checkForNull(Values[10]));
public static String checkForNull(String val) {
return (val == null ? " " : val);
}

error: [["c154ab40-1aaf-11e7-92ae-000c298f510d", "3044c8f0-1ab0-11e7-92ae-000c298f510d"]]

I am working on neo4j database .
And I am using this :
query="match(n:learner) where "+endTime+"<=n.registrationtime<="+startTime+" "+ " return count(n) as total,collect(n.name) as name,"
to retrieve the data on a specific counter but collect function returns data in array form . When I am taking this in String variable it returns value like this
["c154ab40-1aaf-11e7-92ae-000c298f510d",
"3044c8f0-1ab0-11e7-92ae-000c298f510d"]
I want this data in Array list so how can I convert this in arraylist.
I am using this code
try {
query="match(n:learner) where "+endTime+"<=n.registrationtime<="+startTime+" "
+ " return count(n) as total,collect(n.name) as name";
System.out.println(query);
ResultSet rs = stmt.executeQuery(query.toLowerCase());
if(rs.next()){
int total = rs.getInt("total");
System.out.println("total="+total);
ArrayList<String> userids=new ArrayList<String>();
String name=rs.getString("name");
System.out.println("id="+name);
String[] userArray=name.split(",");
for(String user:userArray){
userids.add(user);
System.out.println("userids="+userids);
}
dataFatch.setTotal(total);
and from this code i m getting this result
id=["c154ab40-1aaf-11e7-92ae-000c298f510d","3044c8f0-1ab0-11e7-92ae-000c298f510d"]
userids=[["c154ab40-1aaf-11e7-92ae-000c298f510d"]
userids=[["c154ab40-1aaf-11e7-92ae-000c298f510d",
"3044c8f0-1ab0-11e7-92ae-000c298f510d"]]

for(String user:userArray){
userids.add(user);
}
System.out.println("userids="+userids);
userids is an ArrayList. You just need to print it out of the loop, otherwise userids is printed at any iteration
to print them run this code afterwards:
for (String userid : userids){
System.out.println("userid="+userid);
}

How to read data from list<Object> in Java?

I have a list of objects List , being the result of a HQL Query. The Objects of the list contain the data I need. I am doing the following if I know the types of the data :
(Here I know that the query was Select country, globalAmount, average from table)
for (Object record : result) {
Object[] fields = (Object[]) record;
String country = (String) fields[0];
long globalAmount = (Long) fields[1];
double average = (Double) fields[2];
System.out.println("Country "+country );
System.out.println("Global Amount "+globalAmount);
}
The problem is that sometimes, I don't know if I'll be having "Country" or "average" in the Object, and the query can be completely different :
Select average, date, message from table
Then, to retreive data, I have to do the following :
for (Object record : result) {
Object[] fields = (Object[]) record;
double average = (Double) fields[0];
Timestamp date= (Timestamp) fields[1];
String message = (String) fields[2];
System.out.println("date " +date);
System.out.println("Message "+Message);
System.out.println("Average " + Average);
}
Is there any way that I can dynamically retreive data from this List without having Cast problems?
Thank you for your help!

This is just a proto-type. What I did here is got all the column names and then based on the column name I'm type casting it to the required type.
This is just a small trick.
String query = "Select x, y, z from tablename";
//get the columns here
String colums = query.substring(7, query.indexOf("from") - 1).trim();
String []arrColums = colums.split(",");
for(int i = 0; i < arrColums.length; i++)
{
switch(arrColums[i])
{
case "X" : X x = (X)result.get(i);
case "Y" : Y y = (Y)result.get(i);
}
}

It does not to seem possible. I had to use If blocks to figure out which type I am receiving. Quite long but did not have any other option. The solution provided by Uma Kanth is smart but was not suitable for me though.

how to create comma separated string in single quotes from arraylist of string in JAVA

I have requirement in Java to fire a query on MS SQL like
select * from customer
where customer.name in ('abc', 'xyz', ...,'pqr');
But I have this IN clause values in the form of ArrayList of String. For ex: the list look like {"abc","xyz",...,"pqr"}
I created a Prepared Statement :
PreparedStatement pStmt = conn.prepareStatement(select * from customer
where customer.name in (?));
String list= StringUtils.join(namesList, ",");
pStmt.setString(1,list);
rs = pStmt.executeQuery();
But the list is like "abc,xyz,..,pqr", but I want it as "'abc','xyz',..,'pqr'"
so that I can pass it to Prepares Statement.
How to do it in JAva with out GUAVA helper libraries.
Thanks in Advance!!

I know this is a really old post but just in case someone is looking for how you could do this in a Java 8 way:
private String join(List<String> namesList) {
return String.join(",", namesList
.stream()
.map(name -> ("'" + name + "'"))
.collect(Collectors.toList()));
}

List<String> nameList = ...
String result = nameList.stream().collect(Collectors.joining("','", "'", "'"));

For converting the string you can try this:
String list= StringUtils.join(namesList, "','");
list = "'" + list + "'";
But i dont thing it's a good idea to pass one string for multiple params.

Even if you formatted the String as you wish, it won't work. You can't replace one placeholder in the PreparedStatement with multiple values.
You should build the PreparedStatement dynamically to have as many placeholders as there are elements in your input list.
I'd do something like this :
StringBuilder scmd = new StringBuilder ();
scmd.append ("select * from customer where customer.name in ( ");
for (int i = 0; i < namesList.size(); i++) {
if (i > 0)
scmd.append (',');
scmd.append ('?');
}
scmd.append (")");
PreparedStatement stmt = connection.prepareStatement(scmd.toString());
if (namesList.size() > 0) {
for (int i = 0; i < namesList.size(); i++) {
stmt.setString (i + 1, namesList.get(i));
}
}
rs = stmt.executeQuery();

You can use a simple separator for this type of activity. Essentially you want an object that evaluates to "" the first time around but changes after the first request to return a defined string.
public class SimpleSeparator<T> {
private final String sepString;
boolean first = true;
public SimpleSeparator(final String sep) {
this.sepString = sep;
}
public String sep() {
// Return empty string first and then the separator on every subsequent invocation.
if (first) {
first = false;
return "";
}
return sepString;
}
public static void main(String[] args) {
SimpleSeparator sep = new SimpleSeparator("','");
System.out.print("[");
for ( int i = 0; i < 10; i++ ) {
System.out.print(sep.sep()+i);
}
System.out.print("]");
}
}

I did it as following with stream. Almost the same, but a bit shorter.
nameList = List.of("aaa", "bbb", "ccc")
.stream()
.map(name -> "'" + name + "'")
.collect(Collectors.joining(","));

I guess the simplest way to do it is using expression language like that:
String[] strings = {"a", "b", "c"};
String result = ("" + Arrays.asList(strings)).replaceAll("(^.|.$)", "\'").replace(", ", "\',\'" );

Write Java Vector To Delimited File

I am connecting to an Oracle database and querying multiple tables. My current code creates the connection and calls a PL/SQL function which contains the query. Once I have the result set, I add it to a Vector (as I am unsure the number of records each query will result in).
My problem is that I am unsure how to write a delimited file from the Vector. I imagine once I have added my result set to it, it is simply one gigantic string. I need to be able to receive each field from the query and delimit between them, as well as keep rows separate.
Here is my code:
public static void main(String[] args) throws SQLException {
// instantiate db connection
try {
Class.forName("oracle.jdbc.driver.OracleDriver");
}catch (Exception e) {
throw new SQLException("Oracle JDBC is not available", e);
}
// define connection string and parameters
String url = "jdbc:oracle:thin:#//host:port/sid";
Connection conn = DriverManager.getConnection(url, "USERNAME","PASSWORD");
CallableStatement stmt = conn.prepareCall("{? = CALL <functionname>(?)}");
// get result set and add to a Vector
ResultSet rs = stmt.executeQuery();
Vector<String> results = new Vector();
while ( rs.next() ){
results.add(rs.getString(1));
}
// close result set, sql statement, and connection
rs.close();
stmt.close();
conn.close();
// write Vector to output file,
// where the file name format is MMddyyyy.txt
try {
Calendar cal = Calendar.getInstance();
SimpleDateFormat sdf = new SimpleDateFormat("MMddyyyy");
String dateStr = sdf.format(cal.getTime());
FileWriter fwrite = new FileWriter(dateStr + ".txt");
BufferedWriter out = new BufferedWriter(fwrite);
for(int i = 0; i < results.size(); i++)
{
String temp = results.elementAt(i);
out.write(temp);
}
out.close();
}catch (Exception e) {
System.err.println("Error: " + e.getMessage());
}
}
I am just unsure how to go about getting the information from the db and writing it to a delimited file. Thanks in advance!

If you are unsure about the number of fields in each of your rows, then probably, it won't be possible. Because to fetch all the field values from database, you need to know what is the type of each fields, and the number of fields.
But, I'll post an example for when you have fixed number of fields, that you know.
Suppose you have 4 columns per row. Now to display it in tabular form, you would have to use List of List.
If you are using Vector, use Vector of List.
Here's an example for List of List: -
List<List<String>> results = new ArrayList<List<String>>();
while ( rs.next() ) {
List<String> tempList = new ArrayList<String>();
tempList.add(rs.getString(1));
tempList.add(rs.getString(2));
tempList.add(rs.getString(3));
tempList.add(rs.getString(4));
results.add(tempList);
}
Then to print it, use this loop: -
for (List<String> innerList: results) {
for (String fields: innerList) {
System.out.print(fields + "\t");
}
System.out.println();
}
You can write it in the same form to your BufferedWriter.

Use results.toString() and truncate the braces([]) from resulting string to write all values as comma separated at once in the file.
//toString() returns comma separated string values enclosed in []
String resultString = results.toString();
//truncate leading '[' and termincating ']'
resultString = resultString.substring(1, resultString.length()-1);
//if comma is not your delimiter then use String.replaceAll()
//to replace `,` with your delimiter
//write comma separated elements all at once
out.write(resultString);
So here if you have added str1, str2 in the results Vector, then resultString with have value as str1, str2, which you may write at once using your BufferedWriter out.
Also please use Generics in both the sides of initialization as:
Vector<String> results = new Vector<String>();