Using a Buffer reader I parse throughout a file. If Oranges: pattern is found, I want to replace it with ApplesAndOranges.
try (BufferedReader br = new BufferedReader(new FileReader(resourcesFilePath))) {
String line;
while ((line = br.readLine()) != null) {
if (line.startsWith("Oranges:")){
int startIndex = line.indexOf(":");
line = line.substring(startIndex + 2);
String updatedLine = "ApplesAndOranges";
updateLine(line, updatedLine);
I call a method updateLine and I pass my original line as well as the updated line value.
private static void updateLine(String toUpdate, String updated) throws IOException {
BufferedReader file = new BufferedReader(new FileReader(resourcesFilePath));
PrintWriter writer = new PrintWriter(new File(resourcesFilePath+".out"), "UTF-8");
String line;
while ((line = file.readLine()) != null)
{
line = line.replace(toUpdate, updated);
writer.println(line);
}
file.close();
if (writer.checkError())
throw new IOException("Can't Write To File"+ resourcesFilePath);
writer.close();
}
To get the file to update I have to save it with a different name (resourcesFilePath+".out"). If I use the original file name the saved version become blank.
So here is my question, how can I replace a line with any value in the original file without losing any data.
For this you need to use the regular expressions (RegExp) like this:
str = str.replaceAll("^Orange:(.*)", "OrangeAndApples:$1");
It's an example and maybe it's not excactly what you want, but here, in the first parameter, the expression in parentesis is called a capturing group. The expression found will be replaced by the second parameter and the $1 will be replaced by the value of the capturing group. In our example Orange:Hello at the beggining of a line will be replaced by OrangeAndApples:Hello.
In your code, it seams you create one file per line ... maybe inlining the sub-method would be better.
try (
BufferedReader br = new BufferedReader(new FileReader(resourcesFilePath));
BufferedWriter writer = Files.newBufferedWriter(outputFilePath, charset);
) {
String line;
while ((line = br.readLine()) != null) {
String repl = line.replaceAll("Orange:(.*)","OrangeAndApples:$1");
writer.writeln(repl);
}
}
The easiest way to write over everything in your original final would be to read in everything - changing whatever you want to change and closing the stream. Afterwards open up the file again, then overwrite the file and all its lines with the data you want.
You can use RandomAccessFile to write to the file, and nio.Files to read the bytes from it. In this case, I put it as a string.
You can also read the file with RandomAccessFile, but it is easier to do it this way, in my opinion.
import java.io.RandomAccessFile;
import java.io.File;
import java.io.IOException;
import java.nio.file.*;
public void replace(File file){
try {
RandomAccessFile raf = new RandomAccessFile(file, "rw");
Path p = Paths.get(file.toURI());
String line = new String(Files.readAllBytes(p));
if(line.startsWith("Oranges:")){
line.replaceAll("Oranges:", "ApplesandOranges:");
raf.writeUTF(line);
}
raf.close();
} catch (IOException e) {
e.printStackTrace();
}
}
Related
My input text file is :-
kiShore,kUMar,bhAvanam
My output file must be:-
Kishore,Kumar,Reddy
Simply my code needs to capitalize the 1st letters in file
and This is my code
public static void main(String[] args) throws Exception {
// write your code here
BufferedReader br = new BufferedReader(new FileReader("input.txt"));
FileWriter fw = new FileWriter("output.txt");
String line;
while ((line = br.readLine()) != null) {
String[] values = line.split(",");
for (String str : values) {
String msg = str.substring(0, 1).toUpperCase() + str.substring(1).toLowerCase();
br.mark(0);
if (br.read()!= -1)
{
msg=msg+",";
br.reset();
}
fw.write(msg);
}
}
fw.close();
br.close();
}
My code Works perfectly when file contains multiple lines like:
kIshore,kUMar
rEdDy
i get the exact output
Kishore,Kumar,Reddy
but if my Input file contains only a single line like:
kiShore,kUMar,bhAvanam
I get the output KishoreKumarBhavanam.
I'm unable to insert commas in between words, if the input file contains only a single line
Expected result:
Kishore,kumar,Bhavanam
actual result:
KishoreKumarReddy
As per your code, the problem is you are only adding comma, when your buffered reader can read next character. But, the problem is since you have already read the whole line, there is no additional data to be read. Now, since there is nothing to read, the br.read() function call would return -1 and comma would not be added into your output.
You may observe the same behavior for multi-line file as well, where for the last line of input, the commas are not added.
To fix this, instead on relying on br.read() function, use index while looping and add comma, incase the item is not the last element in the list or use StringJoiner
I think you could do something like this:
import java.io.BufferedReader;
import java.io.FileWriter;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.StringJoiner;
// ...
InputStream inputStream = ParseFile.class.getResourceAsStream("/input.txt");
BufferedReader br = new BufferedReader(new InputStreamReader(inputStream));
FileWriter fw = new FileWriter("output.txt");
String line;
StringJoiner stringJoiner = new StringJoiner(",");
while ((line = br.readLine()) != null) {
String[] values = line.split(",");
for (String str : values) {
stringJoiner.add(str.trim());
}
}
fw.write(stringJoiner.toString());
fw.close();
br.close();
First off I am new at coding in java. I have done extensive research prior to posting this question but have not found the exact answer to my question. I am sure it is my lack of experience, but any assistance the community can provide would be much appreciated.
I am trying to debug a utility class that I have coded. The code is working except for the bit about adding a new line to the substituted text.
Here is the piece of code that is generating an error in NetBeans IDE. The error is incompatible types: Boolean can't be converted to int
try (BufferedWriter bw = new BufferedWriter(new FileWriter (NewCSVFile),true))
What I am trying to do is get this code to read a CSV text file, substitute and the write the new csv data to a new file but preserve the original new lines in the file. And, I want to ensure that the method used is platform independent thus why I am using BufferedWriter.
Here is all the code for your review.
public class TxtFileConverter {
public static void main (String[] args) {
// Location of the file you want to work with.
File CSVFile = new File("/Users/data.csv");
File NewCSVFile = new File("/Users/NewData.csv");
String search = "[,](?!\\w)";
String replace = ",0";
try{
FileReader fr = new FileReader(CSVFile);
String s;
String totalStr = "";
try (BufferedReader br = new BufferedReader(fr)) {
while ((s = br.readLine()) != null) {
totalStr += s;
}
totalStr = totalStr.replaceAll(search, replace);
try (BufferedWriter bw = new BufferedWriter(new FileWriter
(NewCSVFile),true)) {
bw.write(totalStr);
bw.newLine();
}
}
}catch(IOException e){
}
}
}
I think you are trying to read some lines from a file and write it to another file. In the output file, you get all the code in a single line.
I think the bug is in this piece of code.
while ((s = br.readLine()) != null) {
totalStr += s;
}
If you add a statement to add a new line character after reading a line from input file, you should get the desired output.
while ((s = br.readLine()) != null) {
totalStr += s;
totalStr += "\n";
}
The following code adds a newline character at the end of the file.
bw.newLine();
What do you think that true argument is doing in the BufferedWriter constructor? The second and optional argument is the buffer size, an integer. You probably don't even need to supply that argument unless you're doing something rather odd.
try (BufferedWriter bw = new BufferedWriter(new FileWriter(NewCSVFile)))
BufferedWriter has only two constructors:
public BufferedWriter(Writer out) //sz = defaultCharBufferSize = 8192
public BufferedWriter(Writer out, int sz) //sz Output-buffer size, a positive integer
There is no option with second boolean argument. I recommend to use first constructor in your case.
How do you read and display data from .txt files?
BufferedReader in = new BufferedReader(new FileReader("<Filename>"));
Then, you can use in.readLine(); to read a single line at a time. To read until the end, write a while loop as such:
String line;
while((line = in.readLine()) != null)
{
System.out.println(line);
}
in.close();
If your file is strictly text, I prefer to use the java.util.Scanner class.
You can create a Scanner out of a file by:
Scanner fileIn = new Scanner(new File(thePathToYourFile));
Then, you can read text from the file using the methods:
fileIn.nextLine(); // Reads one line from the file
fileIn.next(); // Reads one word from the file
And, you can check if there is any more text left with:
fileIn.hasNext(); // Returns true if there is another word in the file
fileIn.hasNextLine(); // Returns true if there is another line to read from the file
Once you have read the text, and saved it into a String, you can print the string to the command line with:
System.out.print(aString);
System.out.println(aString);
The posted link contains the full specification for the Scanner class. It will be helpful to assist you with what ever else you may want to do.
In general:
Create a FileInputStream for the file.
Create an InputStreamReader wrapping the input stream, specifying the correct encoding
Optionally create a BufferedReader around the InputStreamReader, which makes it simpler to read a line at a time.
Read until there's no more data (e.g. readLine returns null)
Display data as you go or buffer it up for later.
If you need more help than that, please be more specific in your question.
I love this piece of code, use it to load a file into one String:
File file = new File("/my/location");
String contents = new Scanner(file).useDelimiter("\\Z").next();
Below is the code that you may try to read a file and display in java using scanner class. Code will read the file name from user and print the data(Notepad VIM files).
import java.io.*;
import java.util.Scanner;
import java.io.*;
public class TestRead
{
public static void main(String[] input)
{
String fname;
Scanner scan = new Scanner(System.in);
/* enter filename with extension to open and read its content */
System.out.print("Enter File Name to Open (with extension like file.txt) : ");
fname = scan.nextLine();
/* this will reference only one line at a time */
String line = null;
try
{
/* FileReader reads text files in the default encoding */
FileReader fileReader = new FileReader(fname);
/* always wrap the FileReader in BufferedReader */
BufferedReader bufferedReader = new BufferedReader(fileReader);
while((line = bufferedReader.readLine()) != null)
{
System.out.println(line);
}
/* always close the file after use */
bufferedReader.close();
}
catch(IOException ex)
{
System.out.println("Error reading file named '" + fname + "'");
}
}
}
If you want to take some shortcuts you can use Apache Commons IO:
import org.apache.commons.io.FileUtils;
String data = FileUtils.readFileToString(new File("..."), "UTF-8");
System.out.println(data);
:-)
public class PassdataintoFile {
public static void main(String[] args) throws IOException {
try {
PrintWriter pw = new PrintWriter("C:/new/hello.txt", "UTF-8");
PrintWriter pw1 = new PrintWriter("C:/new/hello.txt");
pw1.println("Hi chinni");
pw1.print("your succesfully entered text into file");
pw1.close();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (UnsupportedEncodingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
BufferedReader br = new BufferedReader(new FileReader("C:/new/hello.txt"));
String line;
while((line = br.readLine())!= null)
{
System.out.println(line);
}
br.close();
}
}
In Java 8, you can read a whole file, simply with:
public String read(String file) throws IOException {
return new String(Files.readAllBytes(Paths.get(file)));
}
or if its a Resource:
public String read(String file) throws IOException {
URL url = Resources.getResource(file);
return Resources.toString(url, Charsets.UTF_8);
}
You most likely will want to use the FileInputStream class:
int character;
StringBuffer buffer = new StringBuffer("");
FileInputStream inputStream = new FileInputStream(new File("/home/jessy/file.txt"));
while( (character = inputStream.read()) != -1)
buffer.append((char) character);
inputStream.close();
System.out.println(buffer);
You will also want to catch some of the exceptions thrown by the read() method and FileInputStream constructor, but those are implementation details specific to your project.
I've a code which replaces 10:A to 12:A in a text file called sample.txt. Also, the code I've now is changing the file format, which shouldn't. Can someone please let me know how to do the same using regular expression in Java which doesn't change the file format? File has original format as below 10:A 14:Saxws But after executing the code it outputs as 10:A 14:Saxws.
import java.io.*;
import java.util.*;
public class FileReplace
{
List<String> lines = new ArrayList<String>();
String line = null;
public void doIt()
{
try
{
File f1 = new File("sample.txt");
FileReader fr = new FileReader(f1);
BufferedReader br = new BufferedReader(fr);
while ((line = br.readLine()) != null)
{
if (line.contains("10:A"))
line = line.replaceAll("10:A", "12:A") + System.lineSeparator();
lines.add(line);
}
fr.close();
br.close();
FileWriter fw = new FileWriter(f1);
BufferedWriter out = new BufferedWriter(fw);
for(String s : lines)
out.write(s);
out.flush();
out.close();
}
catch (Exception ex)
{
ex.printStackTrace();
}
}
public static void main(String[] args)
{
FileReplace fr = new FileReplace();
fr.doIt();
}
}
It looks like your OS or editor is not able to print correctly line separators generated by System.lineSeparator(). In that case consider
reading content of entire file to string (including original line separators), - then replacing part which you are interested in
and writing replaced string back to your file
You can do it using this code:
Path file = Paths.get("sample.txt");
//read all bytes from file (they will include bytes representing used line separtors)
byte[] bytesFromFile = Files.readAllBytes(file);
//convert themm to string
String textFromFile = new String(bytesFromFile, StandardCharsets.UTF_8);//use proper charset
//replace what you need (line separators will stay the same)
textFromFile = textFromFile.replaceAll("10:A", "12:A");
//write back data to file
Files.write(file, textFromFile.getBytes(StandardCharsets.UTF_8), StandardOpenOption.CREATE);
I wrote the below part of the code but I couldn't bind the arraylist with search and replace
so my csv file is as like below
1/1/1;7/6/1
1/1/2;7/7/1
I want to search the file 1.cfg for 1/1/1 and change it to 7/6/1 and 1/1/2 change to 7/7/1 and it goes so on.
Thank you all in advance
It's now only printing in a new file only the last line of the old File
import java.io.*;
import java.util.ArrayList;
import java.util.List;
public class ChangeConfiguration {
/**
* #param args
* #throws IOException
*/
public static void main(String[] args)
{
try{
// Open the file that is the first
// command line parameter
FileInputStream degistirilecek = new FileInputStream("c:/Config_Changer.csv");
FileInputStream config = new FileInputStream("c:/1.cfg");
// Get the object of DataInputStream
DataInputStream in = new DataInputStream(config);
DataInputStream degistir = new DataInputStream(degistirilecek);
BufferedReader br = new BufferedReader(new InputStreamReader(in));
BufferedReader brdegis = new BufferedReader(new InputStreamReader(degistir));
List<Object> arrayLines = new ArrayList<Object>();
Object contents;
while ((contents = brdegis.readLine()) != null)
{
arrayLines.add(contents);
}
System.out.println(arrayLines + "\n");
String strLine;
//Read File Line By Line
while ((strLine = br.readLine()) != null) {
//Couldn't modify this part error is here :(
BufferedWriter out = new BufferedWriter(new FileWriter("c:/1_new.cfg"));
out.write(strLine);
out.close();
}
in.close();
degistir.close();
}catch (Exception e){//Catch exception if any
System.err.println("Error: " + e.getMessage());
}
}
}
You are opening the file for reading when you declare:
BufferedReader br = new BufferedReader(new InputStreamReader(in));
If you know the entire file will fit in memory, I recommend doing the following :
Open the file and read it's contents in memory into a giant string, then close the file.
Apply your replace in one shot to the giant string.
Open the file and write (e.g use a BufferedWriter) out the contents of the giant string, then close the file.
As a side note, your code as posted will not compile. The quality of the responses you receive are correlated with the quality of the question asked. Always include an SCCE with your question to increase the chance of getting a precise answer to your question.
can you elaborate the purpose of the program?
if it is a simple content replacement in a file.
then just read a line and store it in a string. then use string replace method for replacing a text in a string.
eg:
newStrog=oldString.replace(oldVlue,newValue);