I need to read a file and write it in a new file, the file that I read has it own time stamp, but in the written file I need to replace it with the current time eg( 2020-09-20 19:30 change it to 2020-09-30 01:30) I have been able to read and write it using the following code, but I am struggling with the change time stamp part
FileInputStream inputRead = null;
FileOutputStream outWrite = null;
try{
File infile =new File("test.txt");
File outfile =new File("test_log.txt");
inputRead = new FileInputStream(infile);
outWrite = new FileOutputStream(outfile);
byte[] buffer = new byte[2048];
int length;
while ((length = inputRead.read(buffer)) > 0){
System.getProperty("line.separator");
outWrite.write(buffer, 0, length);
}
inputRead.close();
outWrite.close();
}
catch(IOException ioe){
ioe.printStackTrace();
}
}
Sorry forgot to mention the Line Read is as follows " 20-09-2020 19:30 (Some Parameter) " to "(current date) + (Some Parameter)
Try this
File infile = new File("test.txt");
File outfile = new File("test_log.txt");
DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm");
try (
BufferedReader inputRead = new BufferedReader(new InputStreamReader(new FileInputStream(infile)));
BufferedWriter outWrite = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(outfile)))
) {
String line;
while ((line = inputRead.readLine()) != null) {
outWrite.write(System.lineSeparator());
String modifiedString = line.replaceAll("\\d{4}-\\d{2}-\\d{2} \\d{2}:\\d{2}", dateTimeFormatter.format(LocalDateTime.now()));
outWrite.write(modifiedString);
}
}
Expanding my answer a bit for clarity.
I've added try-with-resources, you don't need to close the streams manually which should otherwise be done in a finally (if it crashes they are left open).
I've added readers which is a higher level api on top of the stream. for convenience.
I've added search and replace on the string using regex that matches your example string. In my example above i'm using strings which could probably be optimized if needed.
String nextTimeStamp = "2020-09-30 01:30";
Path infile = Paths.get("test.txt");
Path outfile = Paths.get("test_log.txt");
try (Stream<String> lines = Files.lines(infile, Charset.defaultCharset());
PrintWriter out = new PrintWriter(outfile.toFile()) {
lines.map(line -> line.replaceAll("\\d{4}-\\d{2}-\\d{2} \\d{2}:\\d{2}", nextTimeStamp)
.forEach(line -> out.println(line));
}
(For a fixed Charset add an extra parameter with this Charset to PrintWriter too.
Java String is for text, byte[] for binary data. And on String one can do replace and other text operations.
line.replaceAll uses a regular expression to match. If you have the exact string to be replaced, you can use line.replace.
The syntax of what is called try-with-resources accepts AutoCloseable's inside try (...) and will ensure the objects are closed even on exception or return/break.
Related
My aim is to read from a large file, process 2 lines at a time, and write the result to a new file(s). These files can get very large, from 1GB to 150GB in size, so I'd like to attempt to do this processing using the least RAM possible
The processing is very simple: The lines split by a tab delimited, certain elements are selected, and the new String is written to the new files.
So far I have attempted using BufferedReader to read the File and PrintWriter to output the lines to a file:
while((line1 = br.readLine()) != null){
if(!line1.startsWith("#")){
line2 = br.readLine();
recordCount++;
one.println(String.format("%s\n%s\n+\n%s",line1.split("\t")[0] + ".1", line1.split("\t")[9], line1.split("\t")[10]));
two.println(String.format("%s\n%s\n+\n%s",line2.split("\t")[0] + ".2", line2.split("\t")[9], line2.split("\t")[10]));
}
}
I have also attempted to uses Java8 Streams to read and write from the file:
stream.forEach(line -> {
if(!line.startsWith("#")) {
try {
if (counter.getAndIncrement() % 2 == 0)
Files.write(path1, String.format("%s\n%s\n+\n%s", line.split("\t")[0] + ".1", line.split("\t")[9], line.split("\t")[10]).getBytes(), StandardOpenOption.APPEND);
else
Files.write(path2, String.format("%s\n%s\n+\n%s", line.split("\t")[0] + ".2", line.split("\t")[9], line.split("\t")[10]).getBytes(), StandardOpenOption.APPEND);
}catch(IOException ioe){
}
}
});
Finally, I have tried to use an InputStream and scanner to read the file and PrintWriter to output the lines:
inputStream = new FileInputStream(inputFile);
sc = new Scanner(inputStream, "UTF-8");
String line1, line2;
PrintWriter one = new PrintWriter(new FileOutputStream(dotOne));
PrintWriter two = new PrintWriter(new FileOutputStream(dotTwo));
while(sc.hasNextLine()){
line1 = sc.nextLine();
if(!line1.startsWith("#")) {
line2 = sc.nextLine();
one.println(String.format("%s\n%s\n+\n%s",line1.split("\t")[0] + ".1", line1.split("\t")[9], line1.split("\t")[10]));
two.println(String.format("%s\n%s\n+\n%s",line2.split("\t")[0] + ".2", line2.split("\t")[9], line2.split("\t")[10]));
}
}
The issue that I'm facing is that the program seems to be storing either the data to write, or the input file data into RAM.
All of the above methods do work, but use more RAM than I'd like them to.
Thanks in advance,
Sam
What you did not try is a MemoryMappedByteBuffer. The FileChannel.map might be usable for your purpose, not allocating in java memory.
Functioning code with a self made byte buffer would be:
try (FileInputStream fis = new FileInputStream(source);
FileChannel fic = fis.getChannel();
FileOutputStream fos = new FileOutputStream(target);
FileChannel foc = fos.getChannel()) {
ByteBuffer buffer = ByteBuffer.allocate(1024);
while (true) {
int nread = fic.read(buffer);
if (nread == -1) {}
break;
}
buffer.flip();
foc.write(buffer);
buffer.clear();
}
}
Using fic.map to consecutively map regions into OS memory seems easy, but
such more complex code I would need to test first.
When creating PrintWriter set autoFlush to true:
new PrintWriter(new FileOutputStream(dotOne), true)
This way the buffered data will be flushed with every println.
I know this is very basic stuff but for some reason I'm having problems with a bufferedReader/ Writer. I am trying to get the first line of text and return it to another method. However, for some reason the writer doesn't seem to be writing to the temp file and it isn't changing the name of the temp file either.
By throwing a few print statements I have been able to figure out:
The while loop is operating correctly
The if else statement is operating correctly
The tempFile is not writing to a text file correctly
The tempFile is not renaming correctly
There are no errors being thrown
private static String wavFinder() throws IOException{
String currentWav=null;
int x = 1;
File inputFile = new File("C:\\convoLists/unTranscribed.txt");
File tempFile = new File("C:\\convoLists/unTranscribedtemp.txt");
BufferedReader reader = new BufferedReader(new FileReader(inputFile));
BufferedWriter writer = new BufferedWriter(new FileWriter(tempFile));
String currentLine = null;
while((currentLine = reader.readLine()) != null) {
if(x == 1){
currentWav = currentLine;
}
else{
writer.write(currentLine);
}
x = 2;
}
boolean successful = tempFile.renameTo(inputFile);
System.out.println("Success: " + successful);
System.out.println("currentWav = " + currentWav);
return currentWav;
}
Here is the method I am using. If you notice anything please let me know and if you have any questions I will be sure to answer them quickly. Thank you :)
First flush the steam(writer) and close them.
You can not have two files with same name. You are trying to rename the temp file with input file. You need to delete input file and then rename it to that.
reader.close();
writer.flush();
writer.close();
inputFile.delete();
Add these lines before rename and it will work
Close your buffers before trying to call renameTo.
reader.close()
writer.close()
File inputFile = new File("C:\convoLists/unTranscribed.txt");
File tempFile = new File("C:\convoLists/unTranscribedtemp.txt");
Why you have different signs for path?
Always should be //.
Assuming I have a txt file located in /mypath/sampletext.txt. How do I append a new line to the beginning of the file with the following in Java while preserving the original text file's contents?:
String startStr ="--Start of File--";
Looking for a way to do this without having to create an intermediary 2nd file and make modifications only to the existing file if possible.
Read file contents first, prepend new line to that like contents = newLine + contents, then write the new conent in the same file (dont append).
well,three ways ,may help you
1.
//true: is append text to fie
FileWriter write = new FileWriter("file_path",true);
writer.write(content);
//open randomFile and "rw"
randomFile = new RandomAccessFile("file_path", "rw");
// file length
long fileLength = randomFile.length();
//point to end index
randomFile.seek(fileLength);
//write
randomFile.writeBytes(content);
BufferedWriter out = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(file, true)));
out.write(conent);
New answer is updated...
In this I've use few more FileIO classes & may be their one is deprecated API but If you are aware with Java FileIO classes you can easily fix it.
Here I append new line at the start of file rather than append it to the end of file..
If any issue please comment again....
Try this, I think it will help you..
try
{
//Append new line in existing file.
FileInputStream fr = new FileInputStream("onlineSoultion.txt");
DataInputStream dr = new DataInputStream(fr);
String startStr = "--Start of File--\n";
//String startStr;
while (dr.available() > 0) {
startStr += dr.readLine();
//System.out.println(startStr);
}
dr.close();
fr.close();
FileOutputStream writer = new FileOutputStream("onlineSoultion.txt");
writer.write((new String()).getBytes());
writer.close();
PrintWriter out = new PrintWriter(new BufferedWriter(new FileWriter("onlineSoultion.txt", true)));
out.println(startStr);
out.close();
}
I have a text file with the following contents:
one
two
three
four
I want to access the string "three" by its position in the text file in Java.I found the substring concept on google but unable to use it.
so far I am able to read the file contents:
import java.io.*;
class FileRead
{
public static void main(String args[])
{
try{
// Open the file that is the first
// command line parameter
FileInputStream fstream = new FileInputStream("textfile.txt");
// Get the object of DataInputStream
DataInputStream in = new DataInputStream(fstream);
BufferedReader br = new BufferedReader(new InputStreamReader(in));
String strLine;
//Read File Line By Line
while ((strLine = br.readLine()) != null) {
// Print the content on the console
System.out.println (strLine);
}
//Close the input stream
in.close();
}catch (Exception e){//Catch exception if any
System.err.println("Error: " + e.getMessage());
}
}
}
I want to apply the substring concept to the file.It asks for the position and displays the string.
String Str = new String("Welcome to Tutorialspoint.com");
System.out.println(Str.substring(10, 15) );
If you know the byte offsets within the file that you are interested in then it's straightforward:
RandomAccessFile raFile = new RandomAccessFile("textfile.txt", "r");
raFile.seek(startOffset);
byte[] bytes = new byte[length];
raFile.readFully(bytes);
raFile.close();
String str = new String(bytes, "Windows-1252"); // or whatever encoding
But for this to work you have to use byte offsets, not character offsets - if the file is encoded in a variable-width encoding such as UTF-8 then there's no way to seek directly to the nth character, you have to start at the top of the file and read and discard the first n-1 characters.
look for \r\n (linebreaks) in your text file. This way you should be able to count the rows containing your string.
your file in reality looks like this
one\r\n
two\r\n
three\r\n
four\r\n
You seem to be looking for this. The code I posted there works on the byte level, so it may not work for you. Another option is to use the BufferedReader and just read a single character in a loop like this:
String getString(String fileName, int start, int end) throws IOException {
int len = end - start;
if (len <= 0) {
throw new IllegalArgumentException("Length of string to output is zero or negative.");
}
char[] buffer = new char[len];
BufferedReader reader = new BufferedReader(new FileReader(fileName));
for (int i = 0; i < start; i++) {
reader.read(); // Ignore the result
}
reader.read(buffer, 0, len);
return new String(buffer);
}
I'm trying to figure out why this doesn't work. All the files which are shown actually exist. The 'logging.toString()' is a .txt file and it reads all the text in the logging and writes it back with the String which I want to be added. Although when I do this, it overwrites it. But I dont want that. Help?
try{
FileWriter fstream = new FileWriter(logging.toString());
BufferedWriter out = new BufferedWriter(fstream);
FileInputStream fstreams = new FileInputStream(logging);
BufferedReader br = new BufferedReader(new InputStreamReader(fstreams));
String strLine;
while ((strLine = br.readLine()) != null){
htmlTextArea = htmlTextArea + strLine + "\n";
}
out.write(htmlTextArea + logto);
out.close();
} catch (Exception ex){}
Why wouldn't it? You don't pass an append flag:
FileWriter(String filename, boolean append)
The API docs are your friend; they're often helpful for understanding behavior.
Change this line
FileWriter fstream = new FileWriter(logging.toString());
to
FileWriter fstream = new FileWriter(logging.toString(), true);
That way, you tell Java you wish to APPEND the file. There's more in the Javadocs for FileWriter.
Because that's the way FileWriter is implemented.
If you want to append, you should use a different constructor: new FileWriter( logging.toString(), true );
If you want to add something to file but not overwrite it use
FileWriter fstream = new FileWriter(logging.toString(),true);