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How to replace a line with a new line using Java

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();
}
}

Unable to a read a large file using BufferedReader in Java

I am trying to read a file using BufferedReader, but when I tried to print, It is returning some weird characters.
Code of reading file is:
private static String readJsonFile(String fileName) throws IOException{
BufferedReader br = null;
try {
StringBuilder sb = new StringBuilder();
br = new BufferedReader(new FileReader(fileName));
String line = br.readLine();
while(line != null ){
sb.append(line);
System.out.println(line);
line=br.readLine();
}
return sb.toString();
} finally{
br.close();
}
}
This function is being called as :
String jsonString = null;
try {
jsonString = readJsonFile(fileName);
} catch (IOException e) {
e.printStackTrace();
}
But when I tried to print this in console using System.out.println(jsonString);, It is returning some fancy pictures.
Note: It is Working file when file size is small.
Is there any limit on size of file it can read ?

You're using the platform default encoding to read the file, which is probably encoded in UTF8. Check the actual encoding of the file, and specify the encoding:
BufferedReader r = new BufferedReader(new InputStreamReader(new FileInputStream("...", StandardCharsets.UTF_8));
Note that since you simply want to read everything from the file, you could simply use
String json = new String(Files.readAllBytes(...), StandardCharsets.UTF_8);

How to convert xml file to string without escaping XML using java

I've a XML file and want to send its content to caller as string. This is what I'm using:
return FileUtils.readFileToString(xmlFile);
but this (or that matter all other ways I tried like reading line by line) escapes XML elements and enclose whole XML with <string> like this
<string>>&lt;.....</string>
but I want to return
<a>....</a>

I'd advise using a different file reader maybe something like this.
private String readFile( String file ) throws IOException {
BufferedReader reader = new BufferedReader( new FileReader (file));
String line = null;
StringBuilder stringBuilder = new StringBuilder();
String ls = System.getProperty("line.separator");
while( ( line = reader.readLine() ) != null ) {
stringBuilder.append( line );
stringBuilder.append( ls );
}
return stringBuilder.toString();
}
It's probably a feature of file utils.

According to your question you just want to read the file. You can use FileReader and BufferedReader to read the file.
File f=new File("demo.xml");
FileReader fr=new FileReader(f);
BufferedReader br=new BufferedReader(fr);
String line;
while((line=br.readLine())!=null)
{
System.out.println(line);
}
Hope this answer helps you

IOUtils works well. It's in package org.apache.commons.io. The toString method takes an InputStream as a parameter and returns the contents as a string maintaining format.
InputStream is = getClass.getResourceAsStream("foo.xml");
String str = IOUtils.toString(is);

BufferedReader br = new BufferedReader(new FileReader(new File(filename)));
String line;
StringBuilder sb = new StringBuilder();
while((line = br.readLine())!= null){
sb.append(line.trim());
}

Reading in pound sign and speech marks

I am currently reading in a file into java where the file contains list of ("char symbol" "tab" "6 comma seperated booleans" "new line")
I am reading it in fine and splitting it up ok - however i have a problem whereby the pound sign and speech marks are being read in as a black diamond with a question mark in it. This is screwing everything up as i need to be able to identify which codes go with which char symbol.
I am reading in using:
public void read()
{
int i = 0;
try{
// Open the file
InputStream is = am.open("combinations.txt");
// Get the object of DataInputStream
DataInputStream in = new DataInputStream(is);
BufferedReader br = new BufferedReader(new InputStreamReader(in));
String strLine;
//Read File Line By Line
while ((strLine = br.readLine()) != null && i < 53) {
String[] sep1 = strLine.split("\t");
String[] sep2 = sep1[1].split(",");
entries[i] = new Entry(sep1[0].charAt(0), new CellPattern(Boolean.valueOf(sep2[0]),
Boolean.valueOf(sep2[1]),Boolean.valueOf(sep2[2]),Boolean.valueOf(sep2[3]),
Boolean.valueOf(sep2[4]),Boolean.valueOf(sep2[5])));
i++;
}
//Close the input stream
in.close();
}catch (Exception e){//Catch exception if any
System.err.println("Error: " + e.getMessage());
}

It is an encoding problem, try changing your BufferedReader line to:
BufferedReader br = new BufferedReader(new InputStreamReader(in, "UTF-8"));
I'm not sure which encoding you'll need, so you may want to try a few different ones.
Edit:
Try "ISO-8859-1"

Java - ignoring certain characters while reading a text file

I'm trying to read a simple text file that contains the following:
LOAD
Bill's Beans
1200
20
15
30
QUIT
I need to store and print the contents line by line. I am doing so using the following code:
String inputFile = "(file path here)";
try {
Scanner input = new Scanner(inputFile);
} catch (FileNotFoundException e) {
e.printStackTrace();
}
String currentLine = "";
while (!currentLine.equals("QUIT}")){
currentLine = input.nextLine();
System.out.println(currentLine);
}
input.close();
However, the output is very "messy". I am trying to avoid storing all new line characters and anything else that doesn't appear in the text file. Output is:
{\rtf1\ansi\ansicpg1252\cocoartf949\cocoasubrtf540
{\fonttbl\f0\fmodern\fcharset0 Courier;}
{\colortbl;\red255\green255\blue255;}
\margl1440\margr1440\vieww9000\viewh8400\viewkind0
\deftab720
\pard\pardeftab720\ql\qnatural
\f0\fs26 \cf0 LOAD\
Bill's Beans\
1200\
20\
15\
30\
QUIT}
Any help would be greatly appreciated, thank you!

This looks like you're reading a RTF file, isn't that so, by any chance?
Otherwise, I found reading text files is most natural for me using this construct:
BufferedReader reader = new BufferedReader(
new FileReader(new File("yourfile.txt")
);
String text = null;
// repeat until all lines is read
while ((text = reader.readLine()) != null) {
// do whatever with the text line
}
Because this is an RTF file, look into this for example: RTFEditorKit

If you insist on writing your own RTF reader, the correct approach would be for you to extend FilterInputStream and handle the RTF metadata in its implementation.

Just add following code into your class, then call it with path parameter. it returns all lines as List object
public List<String> readStudentsNoFromText(String path) throws IOException {
List<String> result = new ArrayList<String>();
// Open the file that is the first
// command line parameter
FileInputStream fstream = new FileInputStream(new File(path));
// 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);
result.add(strLine.trim());
}
//Close the input stream
in.close();
return result;
}