Develop Reference

How can i remove a particular text from a file in java?

I have tried to implement a simple program to delete a particular text from a file, some how it is not able to delete it. I am reading entire file content into a temp file , delete the user input string from it and update the content to the original file.
Any help would be highly appreciated.
public class TextEraser{
public static void main(String[] args) throws IOException {
System.out.print("Enter a string to remove : ");
Scanner scanner = new Scanner(System. in);
String inputString = scanner. nextLine();
// Locate the file
File file = new File("/Users/lobsang/documents/input.txt");
//create temporary file
File temp = File.createTempFile("file", ".txt", file.getParentFile());
String charset = "UTF-8";
try {
// Create a buffered reader
// to read each line from a file.
BufferedReader in = new BufferedReader(new FileReader(file));
PrintWriter writer = new PrintWriter(new OutputStreamWriter(new FileOutputStream(temp), charset));
String s = in.readLine();
// Read each line from the file and echo it to the screen.
while (s !=null) {
s=s.replace(inputString,"");
s = in.readLine();
}
writer.println(s);
// Close the buffered reader
in.close();
writer.close();
file.delete();
temp.renameTo(file);
} catch (FileNotFoundException e1) {
// If this file does not exist
System.err.println("File not found: " + file);
}
}

After replace with input string, write string immediate in file.
while (s != null) {
s = s.replace(inputString, "");
writer.write(s);
// writer.newLine();
s = in.readLine();
}
For new line , use BufferedWriter in place of PrintWriter, it contains method newLine()
writer.newLine();
Remove this
writer.println(s);

read from file and write some parts in another file

I have to read from a text file and format the input. I'm new to java reading from files, and I don't know how to work with just some parts of what I read
Here is the initial file: http://pastebin.com/D0paWtAd
And I have to write in another file the following output:
Average,Joe,44,31,18,12,9,10
I've managed just to take everything from the file and print it to output. I would need help just in taking the output I need and print it to the screen. Any help is appreciated.
This is what I wrote up to now:
public class FileParsing {
public static String
read(String filename) throws IOException {
BufferedReader in = new BufferedReader(new FileReader("C:\\Users\\Bogdi\\Desktop\\example.txt"));
String s;
StringBuilder sb = new StringBuilder();
while((s = in.readLine())!= null) sb.append(s + "\n");
in.close();
return sb.toString();
}

If your goal is to do the specified output in another file you don't need to first get the content of your file in a StringBuilder before processing it, you can append the processed datas directly in a StringBuilder then you can write the result in a file. Here is an example that would work for the given file but you may have to modify it if the keys change in the future:
The following method will correctly process the datas from your file
public static String read(String filename) throws IOException {
BufferedReader in = new BufferedReader(new FileReader(filename));
String s;
StringBuilder sb = new StringBuilder();
while((s = in.readLine())!= null) {
String[] split1 = s.split("=");
if (split1[0].equals("name")) {
StringTokenizer tokenizer = new StringTokenizer(split1[1]);
sb.append(tokenizer.nextToken());
sb.append(",");
sb.append(tokenizer.nextToken());
sb.append(",");
} else if (split1[0].equals("index")) {
sb.append(split1[1] + ",");
} else if (split1[0].equals("FBid")) {
sb.append(split1[1]);
} else {
StringTokenizer tokenizer = new StringTokenizer(split1[1]);
String wasted = tokenizer.nextToken();
sb.append(tokenizer.nextToken() + ",");
}
}
in.close();
return sb.toString();
}
The next method will read any string to a file
public static void writeStringToFile(String string, String filePath) throws IOException {
BufferedWriter writer = new BufferedWriter(
new FileWriter(
new File(filePath)
)
);
writer.write(string);
writer.newLine();
writer.flush();
writer.close();
}
And here is a simple tests (File1.txt contains the datas from the file you shared on paste bin and I write them in another file)
public static void main(String[] args) throws Exception {
String datas = read("C:\\Tests\\File1.txt");
System.out.println(datas);
writeStringToFile(datas, "C:\\Tests\\FileOuput.txt" );
}
It will produce the exact output that you are expecting
[EDIT] #idk, apparently you have an exception executing my example, while it is working fine for me. That could only mean there is an error at data level. Here is the data sample that I used (and I believe I exactly copy the datas you shared)
And here is the result:

Good to know you are using "StringBuilder" component instead being concatenating your String values, way to go :).
More than knowledge on the Java.IO API to work with files, you will need some logic to get the results you expect. Here I came with an approach that could help you, not perfect, but can point you on how to face this problem.
//Reference to your file
String myFilePath = "c:/dev/myFile.txt";
File myFile = new File(myFilePath);
//Create a buffered reader, which is a good start
BufferedReader breader = new BufferedReader(new FileReader(myFile));
//Define this variable called line that will evaluate each line of our file
String line = null;
//I will use a StringBuilder to append the information I need
StringBuilder appender = new StringBuilder();
while ((line = breader.readLine()) != null) {
//First, I will obtain the characters after "equals" sign
String afterEquals = line.substring(line.indexOf("=") + 1, line.length());
//Then, if it contains digits...
if (afterEquals.matches(".*\\d+.*")) {
//I will just get the digits from the line
afterEquals = afterEquals.replaceAll("\\D+","");
}
//Finally, append the contents
appender.append(afterEquals);
appender.append(",");//This is the comma you want to include
}
//I will delete the last comma
appender.deleteCharAt(appender.length() - 1);
//Close the reader...
breader.close();
//Then create a process to write the content
BufferedWriter myWriter = new BufferedWriter(new FileWriter(new File("myResultFile.txt")));
//Write the full contents I get from my appender :)
myWriter.write(appender.toString());
//Close the writer
myWriter.close();
}
Hope this can help you. Happy coding!

android remove known line from txt file

I need to remove one line from txt file and I already know the position of this line.
I know how to replace data on txt file reading whole content but I would like to delete line from specific position. Thank you.
BufferedReader br = new BufferedReader(new FileReader("data/data/"+ PACKAGE_NAME +"/myFile.txt"));
//delete Line on position 2 (as example)
br.close();

You could read all of the lines from the File first and store them in a List<String>. Then you could remove the index and write back all of the lines. Perhaps it might look something like:
public void removeLine(final File file, final int lineIndex) throws IOException{
final List<String> lines = new LinkedList<>();
final Scanner reader = new Scanner(new FileInputStream(file), "UTF-8");
while(reader.hasNextLine())
lines.add(reader.nextLine());
reader.close();
assert lineIndex >= 0 && lineIndex <= lines.size() - 1;
lines.remove(lineIndex);
final BufferedWriter writer = new BufferedWriter(new FileWriter(file, false));
for(final String line : lines)
writer.write(line);
writer.flush();
writer.close();
}
Usage:
public static void main(String args[]) throws IOException{
final File file = ...;
removeLine(file, 2);
}
The code above will remove the 3rd line.

by jni, use
open
mmap
memcpy
munmap
ftruncate
close

StringEscapeUtils.unescapeHtml doesn't work on strings read from files

I'm trying to read in a file that contains unicode characters, convert those characters to their corresponding symbols and then print the resulting text to a new file. I'm trying to use StringEscapeUtils.unescapeHtml to do this but the lines are just being printed as is, with the unicode points still intact. I did a practice run by copying a single line from the file, making a string from that and then calling StringEscapeUtils.unescapeHtml on that, which works perfectly. My code is below:
class FileWrite
{
public static void main(String args[])
{
try{
String testString = " \"text\":\"Dude With Knit Hat At Party Calls Beer \u2018Libations\u2019 http://t.co/rop8NSnRFu\" ";
FileReader instream = new FileReader("Home Timeline.txt");
BufferedReader b = new BufferedReader(instream);
FileWriter fstream = new FileWriter("out.txt");
BufferedWriter out = new BufferedWriter(fstream);
out.write(StringEscapeUtils.unescapeHtml3(testString) + "\n");//This gives the desired output,
//with unicode points converted
String line = b.readLine().toString();
while(line != null){
out.write(StringEscapeUtils.unescapeHtml3(line) + "\n");
line = b.readLine();
}
//Close the output streams
b.close();
out.close();
}
catch (Exception e){//Catch exception if any
System.err.println("Error: " + e.getMessage());
}
}
}

//This gives the desired output,
//with unicode points converted
out.write(StringEscapeUtils.unescapeHtml3(testString) + "\n");
You are mistaken. Java unescapes String literals of this form at compile time when it builds them into the class file:
"\u2018Libations\u2019"
There are no HTML 3 escapes in this code. The method you have chosen is designed to unescape escape sequences of the form ‘.
You probably want the unescapeJava method.

You're strings are being both read and written using your platforms default encoding. You want to explicitly specify the character set to use as 'UTF-8':
Input stream:
BufferedReader b = new BufferedReader(new InputStreamReader(
new FileInputStream("Home Timeline.txt"),
Charset.forName("UTF-8")));
Output stream:
BufferedWriter out = new BufferedWriter(new OutputStreamWriter(
new FileOutputStream("out.txt"),
Charset.forName("UTF-8")));

Reading and displaying data from a .txt file

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.