The problem is that when I read a string and then, try to write each characters in separate line, into a .txt file, although System.out.println will show correct characters, when I write them into a .txt file, for the 's it will write some weird characters instead. To illustrate, here is an example: suppose we have this line Second subject’s layout of same 100 pages. and we want to write it into a .txt file, using the following code:
public static void write(String Swrite) throws IOException {
if(!file.exists()){
file.createNewFile();
}
FileOutputStream fop=new FileOutputStream(file,true);
if(Swrite!=null)
for(final String s : Swrite.split(" ")){
fop.write(s.toLowerCase().getBytes());
fop.write(System.getProperty("line.separator").getBytes());
}
fop.flush();
fop.close();
}
the written file would look like this for the word, subject's: subject’s. I have no idea why this happens.
Try something like the following. It frees you from having to deal with character encoding.
PrintWriter pw = null;
try {
pw = new PrintWriter(file);
if (Swrite!=null)
for (String s : Swrite.split(" ")) {
pw.println(s);
}
}
}
finally {
if (pw != null) {
pw.close();
}
}
How about something like this:
// The file to read the input from and write the output to.
// Original content: Second subject’s layout of same 100 pages.
File file = new File("C:\\temp\\file.txt");
// The charset of the file, in our case UTF-8.
Charset utf8Charset = Charset.forName("UTF-8");
// Read all bytes from the file and create a string out of it (with the correct charset).
String inputString = new String(Files.readAllBytes(file.toPath()), utf8Charset);
// Create a list of all output lines
List<String> lines = new ArrayList<>();
// Add the original line and than an empty line for clarity sake.
lines.add(inputString);
lines.add("");
// Convert the input string to lowercase and iterate over it's char array.
// Than for each char create a string which is a new line.
for(char c : inputString.toLowerCase().toCharArray()){
lines.add(new String(new char[]{c}));
}
// Write all lines in the correct char encoding to the file
Files.write(file.toPath(), lines, utf8Charset);
It all has to do with the used charsets as commented above.
Related
I'm writing a program with a text file in java, what I need to do is to modify the specific string in the file.
For example, the file has a line(the file contains many lines)like "username,password,e,d,b,c,a"
And I want to modify it to "username,password,f,e,d,b,c"
I have searched much but found nothing. How to deal with that?
In general you can do it in 3 steps:
Read file and store it in String
Change the String as you need (your "username,password..." modification)
Write the String to a file
You can search for instruction of every step at Stackoverflow.
Here is a possible solution working directly on the Stream:
public static void main(String[] args) throws IOException {
String inputFile = "C:\\Users\\geheim\\Desktop\\lines.txt";
String outputFile = "C:\\Users\\geheim\\Desktop\\lines_new.txt";
try (Stream<String> stream = Files.lines(Paths.get(inputFile));
FileOutputStream fop = new FileOutputStream(new File(outputFile))) {
stream.map(line -> line += " manipulate line as required\n").forEach(line -> {
try {
fop.write(line.getBytes());
} catch (IOException e) {
e.printStackTrace();
}
});
}
}
You can try like this:
First, read the file line by line and check each line if the string you want to replace exists in that, replace it, and write the content in another file. Do it until you reach EOF.
import java.io.*;
public class Files {
void replace(String stringToReplace, String replaceWith) throws IOException {
BufferedReader in = new BufferedReader(new FileReader("/home/asn/Desktop/All.txt"));
BufferedWriter out = new BufferedWriter(new FileWriter("/home/asn/Desktop/All-copy.txt"));
String line;
while((line=in.readLine())!=null) {
if (line.contains(stringToReplace))
line = line.replace(stringToReplace, replaceWith);
out.write(line);
out.newLine();
}
in.close();
out.close();
}
public static void main(String[] args) throws IOException {
Files f = new Files();
f.replace("amount", "####");
}
}
If you want to use the same file store the content in a buffer(String array or List) and then write the content of the buffer in the same file.
If your file look similar to this:
username:username123,
password:password123,
After load file to String you can do something like this:
int startPosition = file.indexOf("username") + 8; //+8 is length of username with colon
String username;
for(int i=startPosition; i<file.length(); i++) {
if(file.charAt(i) != ',') {
username += Character.toString(file.charAt(i));
} else {
break;
}
System.out.println(username); //should prong username
}
After edit all thing you want to edit, save edited string to file.
There are much ways to solve this issue. Read String docs to get to know operations on String. Without your code we cannot help you enough aptly.
The algorithm is as follows:
Open a temporary file to save edited copy.
Read input file line by line.
Check if the current line needs to be replaced
Various methods of String class may be used to do this:
equals: Compares this string to the specified object. The result is true if and only if the argument is not null and is a String object that represents the same sequence of characters as this object.
equalsIgnoreCase: Compares this String to another String, ignoring case considerations.
contains: Returns true if and only if this string contains the specified sequence of char values.
matches (String regex): Tells whether or not this string matches the given regular expression.
startsWith: Tests if this string starts with the specified prefix (case sensitive).
endsWith: Tests if this string starts with the specified prefix (case sensitive).
There are other predicate functions: contentEquals, regionMatches
If the required condition is true, provide replacement for currentLine:
if (conditionMet) {
currentLine = "Your replacement";
}
Or use String methods replace/replaceFirst/replaceAll to replace the contents at once.
Write the current line to the output file.
Make sure the input and output files are closed when all lines are read from the input file.
Replace the input file with the output file (if needed, for example, if no change occurred, there's no need to replace).
I have a large text file I want to format. Say the input file is called inputFile and output file is called outputFile.
This is my code for using BufferedReader and BufferedWriter
Here is my code
public static void readAndWrite(String fileNameToRead, String fileNameToWrite) {
try{
BufferedReader fr = new BufferedReader(
new FileReader(String.format("%s.txt", fileNameToRead)));
BufferedWriter out = new BufferedWriter(
new FileWriter(String.format("%s.txt", fileNameToWrite), true));
String currentTmp = "";
String tmp = "";
String test = "work \nwork";
out.append(test);
while((tmp = fr.readLine()) != null) {
tmp = tmp.trim();
if(tmp.isEmpty()) {
currentTmp = currentTmp.trim();
out.append(currentTmp);
out.newLine();
out.newLine();
currentTmp = "";
} else {
currentTmp = currentTmp.concat(" ").concat(tmp);
}
}
if(!currentTmp.equals("")) {
out.write(currentTmp);
}
fr.close();
out.close();
} catch (IOException e) {
System.out.println("exception occoured" + e);
}
}
public static void main(String[] args) {
String readFile = "inPutFile";
String writeFile = "outPutFile";
readAndWrite(readFile, writeFile);
}
The problem is that the test string inside the code which have '\n' can we converted to a new line with BufferedWriter. But if I put the same string in the text file it would not perform the same.
In a more easy way to see is that I want my input file have this
work\n
work
and output as
work
work
I am using mac, so the separator should be '\n'
work\n
if you see the "\n" in your file, it is not a new line character. It is just two characters.
The trim() method will not remove those characters.
Instead you might have something like:
if (tmp.endsWith("\n")
tmp = tmp.substring(0, tmp.length() - 2);
I am using mac, so the separator should be '\n'
You should use the newline character for the platform. So when writing to your file the code should be:
} else {
currentTmp = currentTmp.concat(" ").concat(tmp);
out.append( currentTmp );
out.newLine();
}
The newline() method will use the appropriate new line String for the platform.
Edit:
You need to understand what an escape character is in Java. When you use:
String text = "test\n"
and write the string to a file, only 5 characters are written to the file, not 6. The "\n" is an escape sequence which will cause the ascii value for the new line character to be added to the file. This character is not displayable so you can't see it in the file.
After #camickr answer, I think I realized the problem. Some how if I have a text in the file like this
work \nwork
The \n won't be treated as a single char ('\n'), rather it has been treated as two chars. I think thats why when the BufferWriter writes the input string it won't treat it as a new line.
I'm trying to read in a file and modify the text, but I need to keep new lines when doing so. For example, if I were to read in a file that contained:
This is some text.
This is some more text.
It would just read in as
This is some text.This is some more text.
How do I keep that space? I think it has something to do with the /n escape character. I've seen using BufferReader and FileReader, but we haven't learned that in my class yet, so is there another way? What I've tried is something like this:
if (ch == 10)
{
ch = '\n';
fileOut.print(ch);
}
10 is the ASCII table code for a new line, so I thought Java could recognize it as that, but it doesn't.
In Java 8:
You can read lines using:
List<String> yourFileLines = Files.readAllLines(Paths.get("your_file"));
Then collect strings:
String collect = yourFileLines.stream().filter(StringUtils::isNotBlank).collect(Collectors.joining(" "));
The problem is that you (possibly) want to read your file a line at a time, and then you want to write it back a line at a time (keeping empty lines).
The following source does that, it reads the input file one line at a time, and writes it back one line at a time (keeping empty lines).
The only problem is ... it possibly changes the new line, maybe you are reading a unix file and write a dos file or vice-versa depending on the system you are running in and the source type of the file you a reading.
Keeping the original newline can introduce a lot complexity, read BufferedReader and PrintWriter api docs for more information.
public void process(File input , File output){
try(InputStream in = new FileInputStream(input);
OutputStream out = new FileOutputStream(output)){
BufferedReader reader = new BufferedReader(new InputStreamReader(in, "utf-8"),true);
PrintWriter writer = new PrintWriter( new OutputStreamWriter(out,"utf-8"));
String line=null;
while((line=reader.readLine())!=null){
String processed = proces(line);
writer.println(processed);
}
} catch (IOException e) {
// Some exception management
}
}
public String proces(String line){
return line;
}
/n should be \n
if (ch == 10)
{
ch = '\n';
fileOut.print(ch);
}
Is that a typo?
ch = '/n';
otherwise use
ch = '\n';
I have made reference from this question and achieved success in setting up encryption. I am trying to however utilize this encryption on a string of array to write into a file. This is how I am setting my method up but I end up writing only one of the string array into the file.
String[] str = new String ["X: Adam", "Y: Barry", "z: Oliver"];
File file = new File(Path + "/EncryptedFile.txt);
Calling method to write the string array into the file: Crypto.WriteEncrypteFile(str, file);
The method
Public void WriteEncrypteFile(String[] str, File file) {
try {
BufferedWriter w = new BufferedWriter(new FileWriter(file));
byte[] tmptxt = Array.toString(str).getbytes(Charset.forName(" UTF-8 "));
byte[] encTxt = cipher.doFinal(tmptxt);
w.write(string.valueOf(encTxt));
w.flush();
w.close();
} catch (Exception e){
e.printStackTrace();
}
My questions is how can I write an encrypted string from my array into the file. Any pointers?
You are just writing the String value of the array to the file (since you use Array.toString(str)). This will usually just be some representation of the reference. You have to either concatenate the values of the array or loop through it and encrypt/write every value individually.
Additionally, you shouldn't use a Writer to write content that does not consist of characters. Writers always try to encode the output which could potentially ruin your carefully set up bytes.
Just use a FileOutputStream and write the bytes with that:
try( FileOutputStream fos = new FileOutputStream(file) ) {
for(String s : str) {
byte[] tmptxt = s.getbytes(Charset.forName("UTF-8"));
byte[] encTxt = cipher.doFinal(tmptxt);
w.write(encTxt);
}
} catch(IOException e) {
// print error or whatever
}
For reading you do the same thing but with a FileInputStream instead.
You can use Arrays.toString(), but this way you will need to parse it to read it. Alternatively you can also write the byte[] directly in the file using an OutputStream. There's no need to convert to a string unless you want a human (e.g. yourself) to read it.
I am new to Java and trying to save a multi line string to a text file.
Right now, it does work within my application. Like, if I save the file from my application and then open it from my application, it does put a space between lines. However, if I save the file from my app and then open it in Notepad, it is all on one line.
Is there a way to make it show multi line on all programs? Here's my current code:
public static void saveFile(String contents) {
// Get where the person wants to save the file
JFileChooser fc = new JFileChooser();
int rval = fc.showSaveDialog(fc);
if(rval == JFileChooser.APPROVE_OPTION) {
File file = fc.getSelectedFile();
try {
//File out_file = new File(file);
BufferedWriter out = new BufferedWriter(new FileWriter(file));
out.write(contents);
out.flush();
out.close();
} catch(IOException e) {
messageUtilities.errorMessage("There was an error saving your file. IOException was thrown.", "File Error");
}
}
else {
// Do nothing
System.out.println("The user choose not to save anything");
}
}
depending on how you are constructing your string, you may just be running into a line ending problem. Notepad does not support unix line endings (\n only) it only supports windows line endings (\n\r). try opening your saved file using a more robust editor, and/or make sure you are using the proper line endings for your platform. java's system property (System.getProperty("line.separator")) will get you the proper line ending for the platform that the code is running on.
while you're building your string to be saved to the file, rather than explicitly specifying "\n" or "\n\r" (or on the mac "\r") for your line endings, you would instead append the value of that system property.
like so:
String eol = System.getProperty("line.separator");
... somewhere else in your code ...
String texttosave = "Here is a line of text." + eol;
... more code.. optionally adding lines of text .....
// call your save file method
saveFile(texttosave);
Yea as the previous answer mentions the System.getProperty("line.seperator").
your code doesn't show how you created String contents but since you said you were new to java I thought i'd mention that in java concatenating Strings is not nice since it creates a. If you are building the String by doing this:
String contents = ""
contents = contents + "sometext" + "some more text\n"
Then consider using java.lang.StrinBuilder instead
StringBuilder strBuilder = new StringBuilder();
strBuilder.append("sometext").append("somre more text\n");
...
String contents = strBuilder.toString();
Another alternative is to stream what ever your planning to write to a file rather than building a large string and then outputting that.
You could add something like:
contents = contents.replaceAll("\\n","\\n\\r");
if notepad does not display correctly. However you might run into a different problem: at each save/load you will get multiple \r chars. Then to avoid that at load you would have to call the same code above but with reversed parameters. This is really an ugly solution just to get the text to display properly in notepad.
I had this same problem my guy friend, after much thought and research I even found a solution.
You can use the ArrayList to put all the contents of the TextArea for exemple, and send as parameter by calling the save, as the writer just wrote string lines, then we use the "for" line by line to write our ArrayList in the end we will be content TextArea in txt file.
if something does not make sense, I'm sorry is google translator and I who do not speak English.
Watch the Windows Notepad, it does not always jump lines, and shows all in one line, use Wordpad ok.
private void SaveActionPerformed(java.awt.event.ActionEvent evt) {
String NameFile = Name.getText();
ArrayList< String > Text = new ArrayList< String >();
Text.add(TextArea.getText());
SaveFile(NameFile, Text);
}
public void SaveFile(String name, ArrayList< String> message) {
path = "C:\\Users\\Paulo Brito\\Desktop\\" + name + ".txt";
File file1 = new File(path);
try {
if (!file1.exists()) {
file1.createNewFile();
}
File[] files = file1.listFiles();
FileWriter fw = new FileWriter(file1, true);
BufferedWriter bw = new BufferedWriter(fw);
for (int i = 0; i < message.size(); i++) {
bw.write(message.get(i));
bw.newLine();
}
bw.close();
fw.close();
FileReader fr = new FileReader(file1);
BufferedReader br = new BufferedReader(fr);
fw = new FileWriter(file1, true);
bw = new BufferedWriter(fw);
while (br.ready()) {
String line = br.readLine();
System.out.println(line);
bw.write(line);
bw.newLine();
}
br.close();
fr.close();
} catch (IOException ex) {
ex.printStackTrace();
JOptionPane.showMessageDialog(null, "Error in" + ex);
}