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I am trying to make a change log and so I need a single line between some sentences.
All I have is this but it doesn't seem to work. Can anyone help me please?
#Test
public void addLine() {
File temp;
try {
temp = File.createTempFile("app.log", ".tmp", new File("."));
File appLog = new File("app.log");
try (BufferedWriter bw = new BufferedWriter(new FileWriter(temp));
BufferedReader br = new BufferedReader(new FileReader(
appLog))) {
String line;
while ((line = br.readLine()) != null) {
bw.write(line);
bw.newLine();
if ("2 A".equals(line)) {
bw.write("New Line!");
bw.newLine();
}
}
appLog.delete();
temp.renameTo(appLog);
}
} catch (IOException e) {
e.printStackTrace();
}
}
The problem that you might be encountering might be because of the "line separator" used by the BufferedWriter (it gets set when you create said class). I think it would be best to use instead:
System.getProperty("line.separator");
This way you use the System's line separator rather than a hard coded one.
So that your code would look like this:
public void addLine() {
String lineseparator=System.getProperty("line.separator");
// I'd suggest putting this as a class variable, so that it only gets called once rather
// than
// everytime you call the addLine() method
try {
FileWriter stream = new FileWriter(this.log, true);
//If you don't add true as the second parameter, then your file gets rewritten
// instead of appended to
BufferedWriter out = new BufferedWriter(stream);
out.write(lineseparator); //This substitutes your out.newline(); call
out.close();
stream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
##############################################################################.
I will try to be as brief and clear as possible.
I assume that you are opening a file that in my code I call "test.txt" and it's got about a paragraph or so. And that you want that outputted to another file, but with "empty lines" at some points.
Because File() is read line by line, it is much easier to open your main file read a line, and then write it to your log file, then analyse if an empty line is necessary and place it.
Let's see some code then.
// Assume you have a private class variable called
private String lineseparator=System.getProperty("line.separator");
// This method is in charge of calling the method that actually carries out the
// reading and writing. I separate them both because I find it is much cleaner
// to have the try{}catch{} blocks in different methods. Though sometimes for
// logging purposes this is not the best choice
public void addLines() {
try {
readAndWrite();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
// This method is in charge of reading one file and output to another.
public void readAndWrite() throws IOException {
File test = new File("test.txt");
FileWriter writer = writer = new FileWriter(new File("log.txt"), true);
//This FileWriter is in charge of writing to your log file
String line;
boolean conditionToWriteNewLine=true;
//Obviously this needs to be changed to suit your situation
// I just added it for show
BufferedReader reader = new BufferedReader( new FileReader (test));
BufferedWriter out = new BufferedWriter(writer);
//It is in this while loop that you read a line
// Analyze whether it needs to have a new line or not
// and then write it out to log file
while( ( line = reader.readLine() ) != null ) {
out.write(line);
if(conditionToWriteNewLine){
out.write(this.lineseparator);
out.write(this.lineseparator);
//You need to write it twice for an EMPTY LINE
}
}
reader.close();
out.close();
}
One of the big differences from this code is that I only open the files once, while in your code you open the log file every time you want to add a new file. You should read the documentation, so you'll know that every time you open the file, your cursor is pointing to the first line, so anything you add will be added to first line.
I hope this helped you understand some more.
I'm not totally sure what you are asking for, but have you tried setting the "append" flag on true, so the FileWriter will not start a new file, but append content to it at the end? This is done by calling the FileWriter(File, boolean) constructor:
public void addLine() {
try {
FileWriter stream = new FileWriter(this.log, true); // Here!
BufferedWriter out = new BufferedWriter(stream);
out.write("New Extra Line Here");
out.newLine();
out.close();
stream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
I need a single line between some sentences
I guess you mean a new line between other lines of the same file.
To do so you have to read the whole file, locate the place where you want to insert a line, insert the line then write the new content to the file.
This should work fine for small files but if you have large files you might get in trouble.
So you need a more scaleable way of doing it: Read line by line, and write write to a temp file. if you indentify the location where a new line should be inserted, write that line. Continue with the rest of the file. After you are done delete the original file and rename the temp file with the original name.
Pseudocode:
Open actual file
Open temp file
while not end of actual file
Read one line from actual file
Check if new line has to inserted now
Yes: write new line to temp
write line from actual to temp
Close actual file
Close temp file
Delete actual
Rename temp to actual
Code example: (unlike the pseudo code, the new line is inserted after)
Here the line "New Line!" is inserted after each line which is equal to "2 A".
#Test
public void insertNewLineIntoFile() throws IOException {
File temp = File.createTempFile("app.log", ".tmp", new File("."));
File appLog = new File("app.log");
try (BufferedWriter bw = new BufferedWriter(new FileWriter(temp));
BufferedReader br = new BufferedReader(new FileReader(appLog))) {
String line;
while((line = br.readLine()) != null) {
bw.write(line);
bw.newLine();
if("2 A".equals(line)) {
bw.write("New Line!");
bw.newLine();
}
}
appLog.delete();
temp.renameTo(appLog);
}
}
Note that File#delete() and File#renameTo both return a boolean value that is true onyl if the operation was successfull. You absolutely need to check those retuned values and handle accordingly.
out.println("\n");
(instead of out.newLine();)
\n in java declares a new line. If you dont add any text before it then it should just print a blank line like you want.
This will work Correctly.
Suggestion:
out.close(); and stream.close(); should write inside finally block ie they should close even if some exceptions occured.
Related
I am trying to save the multiple line output in a text file from my jTextArea(named as "outputarea" in a code) to my desired path, Everything is OK but the file being saved do not contain the whole output, but only first line oof text. I am using "\n" to break the line in jtextarea while giving multiple line output, does that make any difference or any other problem in this code, This code is just the code on saveAs button, output is coming from another methods I've created. Thanks in Advance!
private void saveAs() {
FileDialog fd = new FileDialog(home.this, "Save", FileDialog.SAVE);
fd.show();
if(fd.getFile()!=null)
{
fn=fd.getFile();
dir=fd.getDirectory();
filename = dir + fn +".txt";
setTitle(filename);
try
{
DataOutputStream d=new DataOutputStream(new FileOutputStream(filename));
holdText = outputarea.getText();
BufferedReader br = new BufferedReader(new StringReader(holdText));
while((holdText = br.readLine())!=null)
{
d.writeBytes(holdText+"\r\n");
d.close();
}
}
catch (Exception e)
{
System.out.println("File not found");
}
outputarea.requestFocus();
save(filename);
}
}
You should put the d.close(); after the completion of while loop, because just after writing the first line in the file using DataOutputStream, you are closing it and you don't let it to fulfill the whole job.
You can see even an error is wrote in your console:
File not found
This is not because it doesn't find your file, it's because in the iterations after the first, it tries to write into a closed stream. So only the first line is wrote then. So change you code like this:
while ((holdText = br.readLine()) != null) {
d.writeBytes(holdText + "\r\n");
}
d.close();
Also I can advise to use a PrintWriter instead of DataOutputStream. Then you can easily change the writeBytes into println method. In this way you don't need to append \r\n manually to each line you write.
Another good hint is to use a try-with-resource (in case you use java 7 or later) or at least a finally block to close your streams either way:
String holdText = outputarea.getText();
try (PrintWriter w = new PrintWriter(new File(filename));
BufferedReader br = new BufferedReader(new StringReader(holdText))) {
while ((holdText = br.readLine()) != null) {
w.println(holdText);
}
} catch (Exception e) {
System.out.println("File not found");
}
Good Luck.
I have a text file with some text in it and i'm planning on replacing certain characters in the text file. So for this i have to read the file using a buffered reader which wraps a file reader.
File file = new File("new.txt");
BufferedReader br = new BufferedReader(new FileReader(file));
String line = null;
while ((line = br.readLine()) != null) {
System.out.println(line);
}
But since i have to edit characters i have to introduce a file writer and add the code which has a string method called replace all. so the overall code will look as given below.
File file = new File("new.txt");
FileWriter fw = new FileWriter(file);
BufferedReader br = new BufferedReader(new FileReader(file));
String line = null;
while ((line = br.readLine()) != null) {
System.out.println(line);
fw.write(br.readLine().replaceAll("t", "1") + "\n");
}
Problem is when i introduce a file writer to the code (By just having the initialization part and when i run the program it deletes the content in the file regardless of adding the following line)
fw.write(br.readLine().replaceAll("t", "1") + "\n");
Why is this occurring? am i following the correct approach to edit characters in a text file?
Or is there any other way of doing this?
Thank you.
public FileWriter(String fileName,
boolean append)
Parameters:
fileName - String The system-dependent filename.
append - boolean if true, then data will be written to the end of the
file rather than the beginning.
To append data use
new FileWriter(file, true);
The problem is that you're trying to write to the file while you're reading from it. A better solution would be to create a second file, put the transformed data into it, then replace the first file with it when you're done. Or if you don't want to do that, read all of the data out of the file first, then open it for writing and write the transformed data.
Also, have you considered using a text-processing language solution such as awk, sed or perl: https://unix.stackexchange.com/questions/112023/how-can-i-replace-a-string-in-a-files
You need to read the file first, and then, only after you read the entire file, you can write to it.
Or you open a different file for writing and then afterwards you replace the old file with the new one.
The reason is that once you start writing to a file, it is truncated (the data that was in the file is deleted).
The only way to avoid that is to open the file in "append" mode. With that mode, you start writing at the end of the file, so you don't delete its content. However, you won't be able to modify the existing content, you will only add content.
Maybe like this
public static void main(String[] args) throws IOException {
try {
File file = new File("/Users/alexanderkrum/IdeaProjects/printerTest/src/atmDep.txt");
Scanner myReader = new Scanner(file);
ArrayList<Integer> numbers = new ArrayList<>();
while (myReader.hasNextLine()) {
numbers.add(myReader.nextInt() + 1);
}
myReader.close();
FileWriter myWriter = new FileWriter(file);
for (Integer number :
numbers) {
myWriter.write(number.toString() + '\n');
}
myWriter.close();
} catch (FileNotFoundException e) {
System.out.println("An error occurred.");
e.printStackTrace();
}
}
Just add at last :
fw.close();
this will close it ,then it will not delete anything in the file.
:)
I am working on a simple save system for my game, which involves three methods, init load and save.
This is my first time trying out reading and writing to/from a file, so I am not sure if I am doing this correctly, therefore I request assistance.
I want to do this:
When the game starts, init is called. If the file saves does not exist, it is created, if it does, load is called.
Later on in the game, save will be called, and variables will be written to the file, line by line (I am using two in this example.)
However, I am stuck on the load function. I have no idea what do past the point I am on. Which is why I am asking, if it is possible to select a certain line from a file, and change the variable to that specific line.
Here is my code, like I said, I have no idea if I am doing this correctly, so help is appreciated.
private File saves = new File("saves.txt");
private void init(){
PrintWriter pw = null;
if(!saves.exists()){
try {
pw = new PrintWriter(new File("saves.txt"));
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}else{
try {
load();
} catch (IOException e) {
e.printStackTrace();
}
}
}
public void save(){
PrintWriter pw = null;
try {
pw = new PrintWriter(new FileOutputStream(new File("saves.txt"), true));
} catch (FileNotFoundException e) {
e.printStackTrace();
}
pw.println(player.coinBank);
pw.println(player.ammo);
pw.close();
}
public void load() throws IOException{
BufferedReader br = new BufferedReader(new FileReader(saves));
String line;
while ((line = br.readLine()) != null) {
}
}
I was thinking of maybe having an array, parsing the string from the text file into a integer, putting it into the array, and then have the variables equal the values from the array.
Seems like your file is a key=value structure, I suggest you'll use Properties object in java.
Here's a good example.
Your file will look like this:
player.coinBank=123
player.ammo=456
To save:
Properties prop = new Properties();
prop.setProperty("player.coinBank", player.getCoinBank());
prop.setProperty("player.ammo", player.getAmmo());
//save properties to project root folder
prop.store(new FileOutputStream("player.properties"), null);
Then you'll load it like this:
Properties prop = new Properties();
prop.load(new FileInputStream("player.properties"));
//get the property value and print it out
System.out.println(prop.getProperty("player.coinBank"));
System.out.println(prop.getProperty("player.ammo"));
Reading and writing are pretty much symmetric.
You're writing player.coinBank as the first line of the file, and player.ammo as the second line. So, when reading, you should read the first line and assign it to player.coinBank, then read the second line and assign it to player.ammo:
public void load() throws IOException{
try (BufferedReader br = new BufferedReader(new FileReader(saves))) {
player.coinBank = br.readLine();
player.ammo = br.readLine();
}
}
Note the use of the try-with-resources statement here, which makes sure the reader is closed, whatever happens in the method. You should also use this construct when writing to the file.
I am new to Java and have been trying to string some open source code together to search tweets and finally was able to succeed. Then I wanted to save the output to a text file. I searched and reviewed console out methods, filewriter, printwriter and I found one on here that works but it's saving only one tweet and overwrites the previous one it saves. How can I properly append the existing text file without overwriting a previous save and make sure it saves all the tweets from the console screen? Example code below:
JSONObject js = new JSONObject(buff.toString());
JSONArray tweets = js.getJSONArray("results");
JSONObject tweet;
for(int i=0;i<tweets.length();i++) {
tweet = tweets.getJSONObject(i);
PrintWriter out;
try {
out = new PrintWriter(new FileWriter("C:\\tweet\\outputfile.txt"));
System.out.println((i+1)+")http://twitter.com/"+tweet.getString("from_user")+" at "+tweet.getString("created_at"));
System.out.println(tweets.getJSONObject(i).getString("text")+"\n");
out.println((i+1)+")http://twitter.com/"+tweet.getString("from_user")+" at "+tweet.getString("created_at"));
out.println(tweets.getJSONObject(i).getString("text")+"\n");
out.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
You are so tantalizingly close. You just need to open the FileWriter with append set to true. Append will make it add to the end of the file, as opposed to overwriting it every time.
out = new PrintWriter(new FileWriter("C:\\tweet\\outputfile.txt", true));
Change this line (Because it will erase your previously written data):
out = new PrintWriter(new FileWriter("C:\\tweet\\outputfile.txt"));
For (Here you are setting Append mode to true)
out = new PrintWriter(new FileWriter("C:\\tweet\\outputfile.txt"), true);
Default mode is set to false so it will overwrite your file.
Instead of creating object of PrintWriter and FileWriter object during each iteration of your for loop you should initialize PrintWriter outside of you for loop(its will improve performance)finally to release resource.
PrintWriter out = null ;
try
{
// putting
out = new PrintWriter(new FileWriter("C:\\tweet\\outputfile.txt"),true); // appending file if exists.
// JSON Parsing instructions
for(int i=0;i<tweets.length();i++)
{
// processing logic and write operation to file
}
}
catch(CustomExceptions e) {//All other exception handling}
catch(Exception e){//Generic exception handling }
finally{
if(out != null
{
out.close();
}
}
public final String path ="your path"
PrintWriter pw = new PrintWriter(new FileWriter(path),true);/*automatically append the line you want to save and if false it will overwrite the data */
pw.write("what ever you want")
pw.close();
I'm working on a program that needs to update a line that depends its value on the result of a line that goes read after. I thought that I could use two BufferedReaders in Java to position the reader on the line to update while the other one goes for the line that fixes the value (it can be an unknown number of lines ahead). The problem here is that I'm using two BufferedReaders on the same file and even if I think I'm doing right with the indexes the result in debug doesn't seem to be reliable.
Here's the code:
String outFinal
FileName=fileOut;
File fileDest=new File(outFinalFileName);
try {
fout = new BufferedWriter(
new OutputStreamWriter(
new FileOutputStream(fileDest)));
} catch (FileNotFoundException e) {
e.printStackTrace();
}
FileReader inputFile=null;
try {
inputFile = new FileReader(inFileName);
} catch (FileNotFoundException e2) {
e2.printStackTrace();
}
BufferedReader fin = new BufferedReader(inputFile);
BufferedReader finChecker = new BufferedReader(inputFile); //Checks the file and matches record to change
String line="";
String lineC="";
int lineNumber=0;
String recordType="";
String statusCode="";
try {
while ((lineC = finChecker.readLine()) != null) {
lineNumber++;
if (lineNumber==1)
line=fin.readLine();
recordType=lineC.substring(0,3);//Gets current Record Type
if (recordType.equals("35")){
while(!line.equals(lineC)){
line=fin.readLine();
if (line==null)
break;
fout.write(line);
}
}else if (recordType.equals("32")){
statusCode=lineC.substring(4,7);
if(statusCode.equals("XX")){
updateRecordLine(line,fout);
}
}
}
returnVal=true;
} catch (IOException e) {
e.printStackTrace();
}
Thanks in advance.
Well, the BufferedReader only reads stuff, it doesn't have the ability to write data back out. So, what you would need is a BufferedReader to get stuff in, and a BufferedWriter that takes all the input from the BufferedReader, and outputs it to a temp file, with the corrected/appended data.
Then, when you're done (i.e. both BufferedReader and BufferedWriter streams are closed), you need to either discard the original file, or rename the temp file to the name of the original file.
You are basically copying the original file to a temp file, modifying the line in question in the temp file's output, and then copying/renaming the temp file over the original.
ok, i see some problem in your code exactly on these lines-->
recordType=lineC.substring(0,3);//Gets current Record Type
if (recordType.equals("35")){
if you see on the first line, you are getting the substring of recordType into recordType. Now recordType length is 3. If at all the recordType has only 2 characters, then substring throws arrayIndexOutOfBoundsException. So when no runtime exceptions, its length is 3 and on the next line you are calling the equals method that has a string with 2 characters.
Will this if block ever run ?