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Insert a string in the middle of text file without replacing [duplicate]

This question already has answers here:
inserting data in the middle of a text file through java
(2 answers)
Closed 9 years ago.
Suppose i have a text file named Sample.text.
i need advice on how to achieve this:
Sample.txt before running a program:
ABCD
while running the program, user will input string to be added starting at the middle
for example: user input is XXX
Sample.txt after running a program:
ABXXXCD

Basically you've got to rewrite the file, at least from the middle. This isn't a matter of Java - it's a matter of what file systems support.
Typically the way to do this is to open both the input file and an output file, then:
Copy the first part from the input file to the output file
Write the middle section to the output file
Copy the remainder of the input file to the output file
Optionally perform file renaming if you want the new file to have the same eventual name as the original file

The basic idea is to read the file contents into memory, say at program start, manipulate the string as desired, then write the entire thing back to the file.
So you would open and read in Sample.txt. In memory you have a string = "ABCD"
in your program execution, accept user input of XXX. Insert that into your string with your favorite string manipulation method. Now string = "ABXXXCD"
Finally you would overwrite Sample.txt with your updated string and close it.
If you were worried about corruption or something, you might save it to a secondary file, then verify its contents, delete the original, and rename the new to be the same as the original.

Actually i have did something like what you want, here try this code, its not a complete but it should give you a clear idea:
public void addString(String fileContent, String insertData) throws IOException {
String firstPart = getFirstPart(fileContent);
Pattern p = Pattern.compile(firstPart);
Matcher matcher = p.matcher(fileContent);
int end = 0;
boolean matched = matcher.find();
if (matched) {
end = matcher.end();
}
if(matched) {
String secondPart = fileContent.substring(end);
StringBuilder newFileContent = new StringBuilder();
newFileContent.append(firstPart);
newFileContent.append(insertData);
newFileContent.append(secondPart);
writeNewFileContent(newFileContent.toString());
}
}

Normally a new file would be created, but the following probably suffices (for non-gigabyte files). Mind the explicit encoding UTF-8; which you can ommit for the encoding of the operating system.
public static void insertInMidstOfFile(File file, String textToInsert)
throws IOException {
if (!file.exists()) {
throw new FileNotFoundException("File not found: " + file.getPath());
// Because file open mode "rw" would create it.
}
if (textToInsert.isEmpty()) {
return;
}
long fileLength = file.length();
long startPosition = fileLength / 2;
long remainingLength = fileLength - startPosition;
if (remainingLength > Integer.MAX_VALUE) {
throw new IllegalStateException("File too large");
}
byte[] bytesToInsert = textToInsert.getBytes(StandardCharsets.UTF_8);
try (RandomAccessFile fh = new RandomAccessFile(file, "rw")) {
fh.seek(startPosition);
byte[] remainder = new byte[(int)remainingLength];
fh.readFully(remainder);
fh.seek(startPosition);
fh.write(bytesToInsert);
fh.write(remainder);
}
}
Java 7 or higher.

Displaying Arabic on Device J2ME

I am using some arabic text in my app. on simulator Arabic Text is diplaying fine.
BUT on device it is not displaying Properly.
On Simulator it is like مَرْحَبًا that.
But on device it is like مرحبا.
My need is this one مَرْحَبًا.

Create text resources for a MIDP application, and how to load them at run-time. This technique is unicode safe, and so is suitable for all languages. The run-time code is small, fast, and uses relatively little memory.
Creating the Text Source
اَللّٰهُمَّ اِنِّىْ اَسْئَلُكَ رِزْقًاوَّاسِعًاطَيِّبًامِنْ رِزْقِكَ
مَرْحَبًا
The process starts with creating a text file. When the file is loaded, each line becomes a separate String object, so you can create a file like:
This needs to be in UTF-8 format. On Windows, you can create UTF-8 files in Notepad. Make sure you use Save As..., and select UTF-8 encoding.
Make the name arb.utf8
This needs to be converted to a format that can be read easily by the MIDP application. MIDP does not provide convenient ways to read text files, like J2SE's BufferedReader. Unicode support can also be a problem when converting between bytes and characters. The easiest way to read text is to use DataInput.readUTF(). But to use this, we need to have written the text using DataOutput.writeUTF().
Below is a simple J2SE, command-line program that will read the .uft8 file you saved from notepad, and create a .res file to go in the JAR.
import java.io.*;
import java.util.*;
public class TextConverter {
public static void main(String[] args) {
if (args.length == 1) {
String language = args[0];
List<String> text = new Vector<String>();
try {
// read text from Notepad UTF-8 file
InputStream in = new FileInputStream(language + ".utf8");
try {
BufferedReader bufin = new BufferedReader(new InputStreamReader(in, "UTF-8"));
String s;
while ( (s = bufin.readLine()) != null ) {
// remove formatting character added by Notepad
s = s.replaceAll("\ufffe", "");
text.add(s);
}
} finally {
in.close();
}
// write it for easy reading in J2ME
OutputStream out = new FileOutputStream(language + ".res");
DataOutputStream dout = new DataOutputStream(out);
try {
// first item is the number of strings
dout.writeShort(text.size());
// then the string themselves
for (String s: text) {
dout.writeUTF(s);
}
} finally {
dout.close();
}
} catch (Exception e) {
System.err.println("TextConverter: " + e);
}
} else {
System.err.println("syntax: TextConverter <language-code>");
}
}
}
To convert arb.utf8 to arb.res, run the converter as:
java TextConverter arb
Using the Text at Runtime
Place the .res file in the JAR.
In the MIDP application, the text can be read with this method:
public String[] loadText(String resName) throws IOException {
String[] text;
InputStream in = getClass().getResourceAsStream(resName);
try {
DataInputStream din = new DataInputStream(in);
int size = din.readShort();
text = new String[size];
for (int i = 0; i < size; i++) {
text[i] = din.readUTF();
}
} finally {
in.close();
}
return text;
}
Load and use text like this:
String[] text = loadText("arb.res");
System.out.println("my arabic word from arb.res file ::"+text[0]+" second from arb.res file ::"+text[1]);
Hope this will help you. Thanks

Java: CSV file read & write

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

What is the best way to generate a unique and short file name in Java

I don't necessarily want to use UUIDs since they are fairly long.
The file just needs to be unique within its directory.
One thought which comes to mind is to use File.createTempFile(String prefix, String suffix), but that seems wrong because the file is not temporary.
The case of two files created in the same millisecond needs to be handled.

Well, you could use the 3-argument version: File.createTempFile(String prefix, String suffix, File directory) which will let you put it where you'd like. Unless you tell it to, Java won't treat it differently than any other file. The only drawback is that the filename is guaranteed to be at least 8 characters long (minimum of 3 characters for the prefix, plus 5 or more characters generated by the function).
If that's too long for you, I suppose you could always just start with the filename "a", and loop through "b", "c", etc until you find one that doesn't already exist.

I'd use Apache Commons Lang library (http://commons.apache.org/lang).
There is a class org.apache.commons.lang.RandomStringUtils that can be used to generate random strings of given length. Very handy not only for filename generation!
Here is the example:
String ext = "dat";
File dir = new File("/home/pregzt");
String name = String.format("%s.%s", RandomStringUtils.randomAlphanumeric(8), ext);
File file = new File(dir, name);

I use the timestamp
i.e
new File( simpleDateFormat.format( new Date() ) );
And have the simpleDateFormat initialized to something like as:
new SimpleDateFormat("File-ddMMyy-hhmmss.SSS.txt");
EDIT
What about
new File(String.format("%s.%s", sdf.format( new Date() ),
random.nextInt(9)));
Unless the number of files created in the same second is too high.
If that's the case and the name doesn't matters
new File( "file."+count++ );
:P

This works for me:
String generateUniqueFileName() {
String filename = "";
long millis = System.currentTimeMillis();
String datetime = new Date().toGMTString();
datetime = datetime.replace(" ", "");
datetime = datetime.replace(":", "");
String rndchars = RandomStringUtils.randomAlphanumeric(16);
filename = rndchars + "_" + datetime + "_" + millis;
return filename;
}
// USE:
String newFile;
do{
newFile=generateUniqueFileName() + "." + FileExt;
}
while(new File(basePath+newFile).exists());
Output filenames should look like :
2OoBwH8OwYGKW2QE_4Sep2013061732GMT_1378275452253.Ext

Look at the File javadoc, the method createNewFile will create the file only if it doesn't exist, and will return a boolean to say if the file was created.
You may also use the exists() method:
int i = 0;
String filename = Integer.toString(i);
File f = new File(filename);
while (f.exists()) {
i++;
filename = Integer.toString(i);
f = new File(filename);
}
f.createNewFile();
System.out.println("File in use: " + f);

If you have access to a database, you can create and use a sequence in the file name.
select mySequence.nextval from dual;
It will be guaranteed to be unique and shouldn't get too large (unless you are pumping out a ton of files).

//Generating Unique File Name
public String getFileName() {
String timeStamp = new SimpleDateFormat("yyyy-MM-dd_HH:mm:ss").format(new Date());
return "PNG_" + timeStamp + "_.png";
}

I use current milliseconds with random numbers
i.e
Random random=new Random();
String ext = ".jpeg";
File dir = new File("/home/pregzt");
String name = String.format("%s%s",System.currentTimeMillis(),random.nextInt(100000)+ext);
File file = new File(dir, name);

Combining other answers, why not use the ms timestamp with a random value appended; repeat until no conflict, which in practice will be almost never.
For example: File-ccyymmdd-hhmmss-mmm-rrrrrr.txt

Why not just use something based on a timestamp..?

Problem is synchronization. Separate out regions of conflict.
Name the file as : (server-name)_(thread/process-name)_(millisecond/timestamp).(extension)
example : aws1_t1_1447402821007.png

How about generate based on time stamp rounded to the nearest millisecond, or whatever accuracy you need... then use a lock to synchronize access to the function.
If you store the last generated file name, you can append sequential letters or further digits to it as needed to make it unique.
Or if you'd rather do it without locks, use a time step plus a thread ID, and make sure that the function takes longer than a millisecond, or waits so that it does.

It looks like you've got a handful of solutions for creating a unique filename, so I'll leave that alone. I would test the filename this way:
String filePath;
boolean fileNotFound = true;
while (fileNotFound) {
String testPath = generateFilename();
try {
RandomAccessFile f = new RandomAccessFile(
new File(testPath), "r");
} catch (Exception e) {
// exception thrown by RandomAccessFile if
// testPath doesn't exist (ie: it can't be read)
filePath = testPath;
fileNotFound = false;
}
}
//now create your file with filePath

This also works
String logFileName = new SimpleDateFormat("yyyyMMddHHmm'.txt'").format(new Date());
logFileName = "loggerFile_" + logFileName;

I understand that I am too late to reply on this question. But I think I should put this as it seems something different from other solution.
We can concatenate threadname and current timeStamp as file name. But with this there is one issue like some thread name contains special character like "\" which can create problem in creating file name. So we can remove special charater from thread name and then concatenate thread name and time stamp
fileName = threadName(after removing special charater) + currentTimeStamp

Why not use synchronized to process multi thread.
here is my solution,It's can generate a short file name , and it's unique.
private static synchronized String generateFileName(){
String name = make(index);
index ++;
return name;
}
private static String make(int index) {
if(index == 0) return "";
return String.valueOf(chars[index % chars.length]) + make(index / chars.length);
}
private static int index = 1;
private static char[] chars = {'a','b','c','d','e','f','g',
'h','i','j','k','l','m','n',
'o','p','q','r','s','t',
'u','v','w','x','y','z'};
blew is main function for test , It's work.
public static void main(String[] args) {
List<String> names = new ArrayList<>();
List<Thread> threads = new ArrayList<>();
for (int i = 0; i < 100; i++) {
Thread thread = new Thread(new Runnable() {
#Override
public void run() {
for (int i = 0; i < 1000; i++) {
String name = generateFileName();
names.add(name);
}
}
});
thread.run();
threads.add(thread);
}
for (int i = 0; i < 10; i++) {
try {
threads.get(i).join();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
System.out.println(names);
System.out.println(names.size());
}

Write XML file (using XStream) to filesystem in Java

I need to be able to serialize a string and then have it save in a .txt or .xml file. I've never used the implementation to read/write files, just remember I am a relative beginner. Also, I need to know how to deserialize the string to be printed out in terminal as a normal string.

XStream has facilities to read from and write to files, see the simple examples (Writer.java and Reader.java) in this article.

If you can serialize it to a txt file, just open an ObjectOutputStream and have it use String's own serialization capability for you.
String str = "serialize me";
String file = "file.txt";
try{
ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream(file));
out.writeObject(str);
out.close();
ObjectInputStream in = new ObjectInputStream(new FileInputStream(file));
String newString = (String) in.readObject();
assert str.equals(newString);
System.out.println("Strings are equal");
}catch(IOException ex){
ex.printStackTrace();
}catch(ClassNotFoundException ex){
ex.printStackTrace();
}
You could also just open a PrintStream and syphon it out that way, then use a BufferedReader and readLine(). If you really want to get fancy (since this is a HW assignment after all), you could use a for loop and print each character individually. Using XML is more complicated than you need to serialize a String and using an external library is just overkill.

If you are beginning Java, then take some time to look through the Apache Commons project. There are lots of basic extensions to java that you will make use of many times.
I'm assuming you just want to persist a string so you can read it back later - in which case it doesn't necessarily need to be XML.
To write a string to a file, see org.apache.commons.io.FileUtils:
FileUtils.writeStringToFile(File file,String data)
To read it back:
FileUtils.readFileToString(File file)
References:
http://commons.apache.org/
http://commons.apache.org/io
http://commons.apache.org/io/api-release/org/apache/commons/io/FileUtils.html
Make sure you also look at commons-lang for lots of good basic stuff.

If you need to create a text file containing XML that represents the contents of an object (and make it bidirectional), just use JSON-lib:
class MyBean{
private String name = "json";
private int pojoId = 1;
private char[] options = new char[]{'a','f'};
private String func1 = "function(i){ return this.options[i]; }";
private JSONFunction func2 = new JSONFunction(new String[]{"i"},"return this.options[i];");
// getters & setters
...
}
JSONObject jsonObject = JSONObject.fromObject( new MyBean() );
String xmlText = XMLSerializer.write( jsonObject );
From there just wrote the String to your file. Much simpler than all those XML API's. Now, however, if you need to conform to a DTD or XSD, this is a bad way to go as it's much more free-format and conforms only to the object layout.
http://json-lib.sourceforge.net/usage.html
Piko

Is there any particular reason to use XStream? This would be extremely easy to do with something like JDOM if all you are doing is trying to serialize a string or two.
Ie, something like:
Document doc = new Document();
Element rootEl = new Element("root");
rootEl.setText("my string");
doc.appendChild(rootEl);
XMLOutputter outputter = new XMLOutputter();
outputter.output(doc);
Some of the details above are probably wrong, but thats the basic flow. Perhaps you should ask a more specific question so that we can understand exactly what problem it is that you are having?

From http://www.xml.com/pub/a/2004/08/18/xstream.html:
import com.thoughtworks.xstream.XStream;
class Date {
int year;
int month;
int day;
}
public class Serialize {
public static void main(String[] args) {
XStream xstream = new XStream();
Date date = new Date();
date.year = 2004;
date.month = 8;
date.day = 15;
xstream.alias("date", Date.class);
String decl = "\n";
String xml = xstream.toXML(date);
System.out.print(decl + xml);
}
}
public class Deserialize {
public static void main(String[] args) {
XStream xstream = new XStream();
Date date = new Date();
xstream.alias("date", Date.class);
String xml = xstream.toXML(date);
System.out.print(xml);
Date newdate = (Date)xstream.fromXML(xml);
newdate.month = 12;
newdate.day = 2;
String newxml = xstream.toXML(newdate);
System.out.print("\n\n" + newxml);
}
}
You can then take the xml string and write it to a file.

try something like this:
FileOutputStream fos = null;
try {
new File(FILE_LOCATION_DIRECTORY).mkdirs();
File fileLocation = new File(FILE_LOCATION_DIRECTORY + "/" + fileName);
fos = new FileOutputStream(fileLocation);
stream.toXML(userAlertSubscription, fos);
} catch (IOException e) {
Log.error(this, "Error %s in file %s", e.getMessage(), fileName);
} finally {
IOUtils.closeQuietly(fos);
}