Develop Reference

Java CSV Reader - Replace Quotes

I am using CSVReader to read the csv file in Java. In my case, the csv file will have double quotes (") and single quotes ('). Something like this.
SL 12" WIR TREE ASST CD
The below code i am using to read the file.
CsvReader reader = null;
reader = readFile(fileName, delimiter, encoding);
while (reader.readRecord()) {
// Code Part
}
Whenever it cross the reader.readrecord(), its throwing the exception as 'Maximum column length of 100,000 exceeded in column 0 in record 0. Set the SafetySwitch property to false if you're expecting column lengths greater than 100,000 characters to avoid this error.'
What i am trying to do and what i need is,
Since i can't able to do any changes in the file, i am trying to replace the double quotes and single quotes to empty string in java. But it is throwing exception, what ever i mentioned above.

I don't know what CsvReader is (it is not part of standard JDK) but the problem seems to occur in readRecord() and thus way before you have the chance to replace any character. So, CsvReader is not usable here and you should use a less specialised reader such as java.io.BufferedReader, for example.
Given, the delimiter is not a quote or double quote (for obvious reasons) then this code snippet works:
File file = new File(fileName);
InputStream is = new FileInputStream(file);
BufferedReader reader = new BufferedReader(new InputStreamReader(is, encoding));
try {
String line = reader.readLine();
while (line != null) {
//replace qoutes
line = line.replace("\"", "");
line = line.replace("'", "");
//split line according to given delimiter
String[] items = line.split(delimiter);
//handle items...
line = reader.readLine();
}
}
catch (IOException e) {
//handle exception...
}

characters not appearing when I print when I import a file?

I'm importing a file into my code and trying to print it. the file contains
i don't like cake.
pizza is good.
i don’t like "cookies" to.
17.
29.
the second dont has a "right single quotation" and when I print it the output is
don�t
the question mark is printed out a blank square. is there a way to convert it to a regular apostrophe?
EDIT:
public class Somethingsomething {
public static void main(String[] args) throws FileNotFoundException,
IOException {
ArrayList<String> list = new ArrayList<String>();
File file = new File("D:\\project1Test.txt");//D:\\project1Test.txt
if(file.exists()){//checks if file exist
FileInputStream fileStream = new FileInputStream(file);
InputStreamReader input = new InputStreamReader(fileStream);
BufferedReader reader = new BufferedReader(input);
String line;
while( (line = reader.readLine()) != null) {
list.add(line);
}
for(int i = 0; i < list.size(); i ++){
System.out.println(list.get(i));
}
}
}}
it should print as normal but the second "don't" has a white block on the apostrophe
this is the file I'm using https://www.mediafire.com/file/8rk7nwilpj7rn7s/project1Test.txt
edit: if it helps even more my the full document where the character is found here
https://www.nytimes.com/2018/03/25/business/economy/labor-professionals.html

It’s all about character encoding. The way characters are represented isn't always the same and they tend to get misinterpreted.
Characters are usually stored as numbers that depend on the encoding standard (and there are so many of them). For example in ASCII, "a" is 97, and in UTF-8 it's 61.
Now when you see funny characters such as the question mark (called replacement character) in this case, it's usually that an encoding standard is being misinterpreted as another standard, and the replacement character is used to replace the unknown or misinterpreted character.
To fix your problem you need to tell your reader to read your file using a specific character encoding, say SOME-CHARSET.
Replace this:
InputStreamReader input = new InputStreamReader(fileStream);
with this:
InputStreamReader input = new InputStreamReader(fileStream, "SOME-CHARSET");
A list of charsets is available here. Unfortunately, you might want to go through them one by one. A short list of most common ones could be found here.

Your problem is almost certainly the encoding scheme you are using. You can read a file in most any encoding scheme you want. Just tell Java how your input was encoded. UTF-8 is common on Linux. Windows native is CP-1250.
This is the sort of problem you have all the time if you are processing files created on a different OS.
See here and Here

I'll give you a different approach...
Use the appropriate means for reading plain text files. Try this:
public static String getTxtContent(String path)
{
try(BufferedReader br = new BufferedReader(new FileReader(path)))
{
StringBuilder sb = new StringBuilder();
String line = br.readLine();
while (line != null) {
sb.append(line);
sb.append(System.lineSeparator());
line = br.readLine();
}
return sb.toString();
}catch(IOException fex){ return null; }
}

Need help using java to read a file, insert trim command, edit the strings, and then save the file as an output

I have two different ways to read the file but I am not sure how to proceed to converting the text to a string and then an if then statement like...
if string contains ":"
true string = "string"
false string = ,,"string"
package test;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
public class ReadStringFromFileLineByLine {
public static void main(String[] args) {
try {
File file = new File("foo.txt");
FileReader fileReader = new FileReader(file);
BufferedReader bufferedReader = new BufferedReader(fileReader);
StringBuffer stringBuffer = new StringBuffer();
String line;
String trim;
while ((line = bufferedReader.readLine()) != null) {
stringBuffer.append(line);
stringBuffer.append("\n");
}
fileReader.close();
System.out.println("Contents of file:");
System.out.println(stringBuffer.toString());
} catch (IOException e) {
e.printStackTrace();
}
}
}
But I don't believe I am using the trim command appropriately

Your question doesn't really communicate clearly the intent of the program. What exactly are you trying to do? If your file is text-based, there is no "conversion to String" needed. Also "save the file as an output" isn't clear either. Do you want to save a new file, overwrite the existing file, or append the existing file. All of these scenarios are handled differently. Taking this by parts:
First point: Your Scantest class works. Given a file foo.txt in the project folder, the class will print out the contents of the file.
Second point: Your class ReadStringFromFileLineByLine works with my own foo.txt just like the first class. So, there might be something wrong with your test.txt file. This is probably the most important thing when testing (making all conditions equal). If the conditions for testing are not equal, the tests will most likely be inconclusive (which is why I suspect happened in your case).
Third point: None of your classes attempted to make any modifications to the obtained strings or made modifications to the file. If you were to write to a file, you have to consider the following: Append vs. Overwrite. All it takes is the use of a simple boolean value:
FileWriter fw = new FileWriter(file.getAbsoluteFile()); // overwrites contents of file
FileWriter fw = new FileWriter(file.getAbsoluteFile(), true); // appends to file
The FileWriter single argument contructor calls the two-argument constructor passing false to it. Therefore, the FileWriter overwrites instead of appends. This is important because if you handle the file line by line, it is possible that at the end, your file will contain only the last line you "modified." If you choose to append, the new String will be added to the end of the line. So this is not good either. If you want to process a file line by line, made modifications to any given line, AND save the line to the same file, your best option is to use RandomAccessFile. This class allows you to write 'X' number of characters starting on a given offset. In this case, this "offset" is the "address" of the current line; putting it simply: the offset is equal to the number of characters already processed. So, for the first line, the offset is 0, for line 2 is the number of characters in line 1, and so forth.
I can add this as an update if you need it, but I did not see anything in your code that attempted to change the file in any way. I was just going by your title.

How to replace multiple occurences of a string in a text file with a variable entered by the user and save all to a new file?

public static void main(String args[])
{
try
{
File file = new File("input.txt");
BufferedReader reader = new BufferedReader(new FileReader(file));
String line = "000000", oldtext = "414141";
while((line = reader.readLine()) != null)
{
oldtext += line + "\r\n";
}
reader.close();
// replace a word in a file
//String newtext = oldtext.replaceAll("drink", "Love");
//To replace a line in a file
String newtext = oldtext.replaceAll("This is test string 20000", "blah blah blah");
FileWriter writer = new FileWriter("input.txt");
writer.write(newtext);writer.close();
}
catch (IOException ioe)
{
ioe.printStackTrace();
}
}
}

A couple suggestions on your sample code:
Have the user pass in old and new on the command line (i.e., args[0] and args1).
If it's sufficient to do this a line at a time, it's going to be much more efficient to read a line, replace old -> new, then stream it out.
Also check out StringUtils and IOUtils, which may make your life easier in this case.

Easiest is the String.replace(oldstring, newstring), or String.replaceAll(regex, newString) function, you can just read the one file and write the replacement into a new file (or do it line by line if you're concerned about file size).

After reading your last comment - that's a totally different story... the preferred solution would be to parse the css file into an object model (like DOM), apply the changes there and serialize the model to css afterwards. It's much easier to find all color attributes in DOM and change them compared to doing the same with search and replace.
I've found some CSS parser in the wild wild web, but none of them looked like being capable of writing CSS files.
If you wanted to replace the color names with search and replace, you'd search for 'color:<colorname>' and replace it with 'color:<youHexColorValue>'. You may have to do the same for 'color:"<colorname>"', because the color name can be set in double quotes (another argument for using a CSS parser..)
String.replaceAll() is the easiest way to do it. Just read the complete CSS file into one String, replace all as suggested above and write the new String to the same (or a temporary) file (first).

How to delete a data from a file through java?

I want to read a file in java. And then, I want to delete a line from that file without the file being re-written.
How can I do this?
Someone suggested me to read/write to a file without the file being re-written with the help of RandomAccessFile. How to write data to a file through java?
Specifically, that files contains lines. One line contains three field - id, name and profession - separated by \t. I want to read that file through a Reader or InputStream or any other way and then search for a line that has the specified keyword (say 121) and then wants to delete that whole line.
This operation needs to be performed without the whole file being re-written

I don't think you can alter a file on a filesystem in any way without writing to it, including deleting a line.
Do you mean you want to write the file without altering the file's metadata, like the last modified time?
Based on your updated question:
I don't think you can do what you're asking to do here. You can't remove bytes from a file once the file has been written, note no deleteByte or removeByte methods in RandomAccessFile.
I suggest moving the content of your file to a database - that allows this kind of record-oriented operation.
The alternative is, you have to rewrite the file. Sorry!

"Lines" are an abstract concept -- they're just an arbitrary sequence of bytes terminated by "\n". BufferedWriters and their ilk don't support textual editing in this way, so you'll have to rewrite the file in its entirety.
In general, what you want to do is:
open a reader
read content into some suitable data structure
close the reader
change data/records which need to be changed in this data structure
open a FileWriter with append == false
write content of data structure to resulting file
close FileWriter

add a marker in your lines saying if your line is deleted or not : this will make a software delete instead od a hardware delete.
if you have to insert new lines, you then can reuse those that are marked as deleted.

The below code searchs the line or fields in a single text file reads the file line by line
then the line or fields can be replaced by " " or any other string. Here we use the pattern and Matcher classes.
If this not clearing your question do let me know.
import java.io.;
import java.util.regex.;
import java.util.Properties;
public class DeleteLine
{
public static void main(String[] args)
{
BufferedReader br = null;
try
{
String line=null;
File f = new File("d:/xyz.txt");
String replaceString=properties.getProperty("replaceAll.String");
;
br = new BufferedReader(new FileReader("d:/giri/scjp/");
while ( (line = br.readLine()) != null )//BufferedReader contains readline method
{
Pattern p=Pattern.compile(searchString);/*here u an specify the line u want to delete */
Matcher m=p.matcher(line);
line=m.replaceAll(replaceString);/*here replace String u can " " so that it will be emptied */
System.out.println(line);
}
//System.out.println(line);
}
}
}
br = new BufferedReader(new FileReader("d:/xyz.txt"));
String line = null;
}
catch (FileNotFoundException e)
{
System.out.println("File couldnt find");
e.printStackTrace();
}
catch (IOException e)
{
e.printStackTrace();
}
}
}