Develop Reference

Creating a File using PrintWriter in Java, and Writing to that File

I'm trying to write a program that reads a file (which is a Java source file), makes an Arraylist of certain specified values from that file. and outputs that Arraylist into another resulting file.
I'm using PrintWriter to make the new resulting file. This is a summarised version of my program:
ArrayList<String> exampleArrayList = new ArrayList<String>();
File actualInputFile = new File("C:/Desktop/example.java");
PrintWriter resultingSpreadsheet= new PrintWriter("C:/Desktop/SpreadsheetValues.txt", "UTF-8");
FileReader fr = new FileReader(actualInputFile);
BufferedReader br = new BufferedReader(fr);
String line=null;
while ((line = br.readLine()) != null) {
// code that makes ArrayList
}
for (int i = 0; i < exampleArrayList.size(); i++) {
resultingSpreadsheet.println(exampleArrayList.get(i));
}
resultingSpreadsheet.close();
The problem is that when i run this, nothing gets printed to the resultingSpreadsheet. It's completely empty.
BUT, this program works perfectly (meaning that it prints out everything correctly to the resultingSpreadsheet file) when I replace:
File actualInputFile = new File("C:/Desktop/example.java");
which is the file that I want as my input file, and which has a size of 481 KB,
with:
File smallerInputFile = new File("C:/Desktop/smallerExample.txt");
which is really just a smaller .txt example version of the .java source file, and it has a size of 1.08 KB.
I've tried a few things including flushing the PrintWriter, wrapping it around FileWriter, copy-pasting all the code from the .java file into a text file in case it was an extension problem, but these don't seem to work.
I'm starting to think it must be because of the size of the file that the PrintWriter makes, but it's very possible that that's not the problem. Perhaps I need to put everything in a stream (like it says here: http://docs.oracle.com/javase/6/docs/api/java/io/PrintWriter.html)? If so, how would I do that?
Why is reading the bigger actualInputFile and outputting its data correctly such a problem, when everything works fine for the smallerInputFile?
Can anyone help with this?

Check for exceptions while writing to the the excel sheet , because i really don't think its a problem of size. Below is the sample code that is executing successfully and the file size was approx 1 MB.
public class Test {
/**
* #param args
*/
public static void main(String[] args) {
BufferedReader br = null;
try {
String sCurrentLine;
br = new BufferedReader(new FileReader("D:\\AdminController.java"));
while ((sCurrentLine = br.readLine()) != null) {
System.out.println(sCurrentLine);
}
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if (br != null)br.close();
} catch (IOException ex) {
ex.printStackTrace();
}
}
}
}

This should go as a comment, but I do not have the rep. In the documentation it has both write methods and print methods. Have you tried using write() instead?
I doubt it's the size of the file, it may be between the two files you are testing one is .txt, and the other is .java
EDIT: Probably second suggestion of the two. First is just something I noticed with the docs.

The methods of PrintWriter do not throw Exception. Call the checkError() method which would flush the stream as well as return true if an error occurred. It is quite possible that an error occurred processing the larger file, an encoding error for instance.

Check your program. When the file is empty it means that your program doesn't close the PrintWriter before finishing the program.
For example you may have a return in a part of your program which cause that resultingSpreadsheet.close(); have not being run.

How to Write text file Java

The following code does not produce a file (I can't see the file anywhere).
What is missing?
try {
//create a temporary file
String timeLog = new SimpleDateFormat("yyyyMMdd_HHmmss").format(
Calendar.getInstance().getTime());
File logFile=new File(timeLog);
BufferedWriter writer = new BufferedWriter(new FileWriter(logFile));
writer.write (string);
//Close writer
writer.close();
} catch(Exception e) {
e.printStackTrace();
}

I think your expectations and reality don't match (but when do they ever ;))
Basically, where you think the file is written and where the file is actually written are not equal (hmmm, perhaps I should write an if statement ;))
public class TestWriteFile {
public static void main(String[] args) {
BufferedWriter writer = null;
try {
//create a temporary file
String timeLog = new SimpleDateFormat("yyyyMMdd_HHmmss").format(Calendar.getInstance().getTime());
File logFile = new File(timeLog);
// This will output the full path where the file will be written to...
System.out.println(logFile.getCanonicalPath());
writer = new BufferedWriter(new FileWriter(logFile));
writer.write("Hello world!");
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
// Close the writer regardless of what happens...
writer.close();
} catch (Exception e) {
}
}
}
}
Also note that your example will overwrite any existing files. If you want to append the text to the file you should do the following instead:
writer = new BufferedWriter(new FileWriter(logFile, true));

I would like to add a bit more to MadProgrammer's Answer.
In case of multiple line writing, when executing the command
writer.write(string);
one may notice that the newline characters are omitted or skipped in the written file even though they appear during debugging or if the same text is printed onto the terminal with,
System.out.println("\n");
Thus, the whole text comes as one big chunk of text which is undesirable in most cases.
The newline character can be dependent on the platform, so it is better to get this character from the java system properties using
String newline = System.getProperty("line.separator");
and then using the newline variable instead of "\n". This will get the output in the way you want it.

In java 7 can now do
try(BufferedWriter w = ....)
{
w.write(...);
}
catch(IOException)
{
}
and w.close will be done automatically

It's not creating a file because you never actually created the file. You made an object for it. Creating an instance doesn't create the file.
File newFile = new File("directory", "fileName.txt");
You can do this to make a file:
newFile.createNewFile();
You can do this to make a folder:
newFile.mkdir();

Using java 8 LocalDateTime and java 7 try-with statement:
public class WriteFile {
public static void main(String[] args) {
String timeLog = DateTimeFormatter.ofPattern("yyyyMMdd_HHmmss").format(LocalDateTime.now());
File logFile = new File(timeLog);
try (BufferedWriter bw = new BufferedWriter(new FileWriter(logFile)))
{
System.out.println("File was written to: " + logFile.getCanonicalPath());
bw.write("Hello world!");
}
catch (IOException e)
{
e.printStackTrace();
}
}
}

You can try a Java Library. FileUtils, It has many functions that write to Files.

It does work with me. Make sure that you append ".txt" next to timeLog. I used it in a simple program opened with Netbeans and it writes the program in the main folder (where builder and src folders are).

The easiest way for me is just like:
try {
FileWriter writer = new FileWriter("C:/Your/Absolute/Path/YourFile.txt");
writer.write("Wow, this is so easy!");
writer.close();
} catch (IOException e) {
e.printStackTrace();
}
Useful tips & tricks:
Give it a certain path:
new FileWriter("C:/Your/Absolute/Path/YourFile.txt");
New line
writer.write("\r\n");
Append lines into existing txt
new FileWriter("log.txt");
Hope it works!

TextArea - Any way to get all text?

so I'm designing a text editor. For the Open/Save methods, I'm trying to use a TextArea (it doesn't have to be one, it's just my current method). Now, I have two problems right now:
1) When I load a file, it currently doesn't remove the contents currently in the text editor. For example, if I typed in "Owl", then loaded a file that contained "Rat", it would end up as "OwlRat". To solve this, I plan to use the replaceRange method (again however, it isn't absolute, any suggestions would be great!). However, I must replace all the contents of the text editor, not just selected text, and I can't figure out how to do that. Any tips?
2) Currently, when I load a file, nothing will happen unless I saved that file the same time I ran the application. So, for example, running the program, saving a file, closing the program, running the program again, and then loading the file will give nothing. I know this is because the String x doesn't carry over, but I can't think of anyway to fix it. Somebody suggested Vectors, but I don't see how they would help...
Here is the code for the Open/Save methods:
Open:
public void Open(String name){
File textFile = new File(name + ".txt.");
BufferedReader reader = null;
try
{
textArea.append(x);
reader = new BufferedReader( new FileReader( textFile));
reader.read();
}
catch ( IOException e)
{
}
finally
{
try
{
if (reader != null)
reader.close();
}
catch (IOException e)
{
}
}
}
Save:
public void Save(String name){
File textFile = new File(name + ".txt");
BufferedWriter writer = null;
try
{
writer = new BufferedWriter( new FileWriter(textFile));
writer.write(name);
x = textArea.getText();
}
catch ( IOException e)
{
}
finally
{
try
{
if ( writer != null)
writer.close( );
}
catch ( IOException e)
{
}
}
}

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 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);
}

There's a lot going on here...
What is 'x' (hint: it's not anything from the file!), and why are you appending it to the text area?
BufferedReader.read() returns one character, which is probably not what you're expecting. Try looping across readline().
Follow Dave Newton's advice to handle your exceptions and provide better names for your variables.
The text file will persist across multiple invocation of your program, so the lack of data has nothing to do with that.
Good luck.

Use textArea.setText(TEXT); rather than append; append means to add on to, so when you append text to a TextArea, you add that text to it. setText on the other hand will set the text, replacing the old text with the new one (which is what you want).
As far as why it's failing to read, you are not reading correctly. First of all, .read() just reads a single character (not what you want). Second, you don't appear to do anything with the returned results. Go somewhere (like here) to find out how to read the file properly, then take the returned string and do textArea.setText(readString);.
And like the others said, use e.printStackTrace(); in all of your catch blocks to make the error actually show up in your console.

Parse a text file into multiple text file

I want to get multiple file by parsing a input file Through Java.
The Input file contains many fasta format of thousands of protein sequence and I want to generate raw format(i.e., without any comma semicolon and without any extra symbol like ">", "[", "]" etc) of each protein sequence.
A fasta sequence starts form ">" symbol followed by description of protein and then sequence of protein.
For example ► >lcl|NC_000001.10_cdsid_XP_003403591.1 [gene=LOC100652771]
[protein=hypothetical protein LOC100652771] [protein_id=XP_003403591.1] [location=join(12190..12227,12595..12721,13403..13639)]
MSESINFSHNLGQLLSPPRCVVMPGMPFPSIRSPELQKTTADLDHTLVSVPSVAESLHHPEITFLTAFCL
PSFTRSRPLPDRQLHHCLALCPSFALPAGDGVCHGPGLQGSCYKGETQESVESRVLPGPRHRH
Like above formate the input file contains 1000s of protein sequence. I have to generate thousands of raw file containing only individual protein sequence without any special symbol or gaps.
I have developed the code for it in Java but out put is : Cannot open a file followed by cannot find file.
Please help me to solve my problem.
Regards
Vijay Kumar Garg
Varanasi
Bharat (India)
The code is
/*Java code to convert FASTA format to a raw format*/
import java.io.*;
import java.util.*;
import java.util.regex.*;
import java.io.FileInputStream;
// java package for using regular expression
public class Arrayren
{
public static void main(String args[]) throws IOException
{
String a[]=new String[1000];
String b[][] =new String[1000][1000];
/*open the id file*/
try
{
File f = new File ("input.txt");
//opening the text document containing genbank ids
FileInputStream fis = new FileInputStream("input.txt");
//Reading the file contents through inputstream
BufferedInputStream bis = new BufferedInputStream(fis);
// Writing the contents to a buffered stream
DataInputStream dis = new DataInputStream(bis);
//Method for reading Java Standard data types
String inputline;
String line;
String separator = System.getProperty("line.separator");
// reads a line till next line operator is found
int i=0;
while ((inputline=dis.readLine()) != null)
{
i++;
a[i]=inputline;
a[i]=a[i].replaceAll(separator,"");
//replaces unwanted patterns like /n with space
a[i]=a[i].trim();
// trims out if any space is available
a[i]=a[i]+".txt";
//takes the file name into an array
try
// to handle run time error
/*take the sequence in to an array*/
{
BufferedReader in = new BufferedReader (new FileReader(a[i]));
String inline = null;
int j=0;
while((inline=in.readLine()) != null)
{
j++;
b[i][j]=inline;
Pattern q=Pattern.compile(">");
//Compiling the regular expression
Matcher n=q.matcher(inline);
//creates the matcher for the above pattern
if(n.find())
{
/*appending the comment line*/
b[i][j]=b[i][j].replaceAll(">gi","");
//identify the pattern and replace it with a space
b[i][j]=b[i][j].replaceAll("[a-zA-Z]","");
b[i][j]=b[i][j].replaceAll("|","");
b[i][j]=b[i][j].replaceAll("\\d{1,15}","");
b[i][j]=b[i][j].replaceAll(".","");
b[i][j]=b[i][j].replaceAll("_","");
b[i][j]=b[i][j].replaceAll("\\(","");
b[i][j]=b[i][j].replaceAll("\\)","");
}
/*printing the sequence in to a text file*/
b[i][j]=b[i][j].replaceAll(separator,"");
b[i][j]=b[i][j].trim();
// trims out if any space is available
File create = new File(inputline+"R.txt");
try
{
if(!create.exists())
{
create.createNewFile();
// creates a new file
}
else
{
System.out.println("file already exists");
}
}
catch(IOException e)
// to catch the exception and print the error if cannot open a file
{
System.err.println("cannot create a file");
}
BufferedWriter outt = new BufferedWriter(new FileWriter(inputline+"R.txt", true));
outt.write(b[i][j]);
// printing the contents to a text file
outt.close();
// closing the text file
System.out.println(b[i][j]);
}
}
catch(Exception e)
{
System.out.println("cannot open a file");
}
}
}
catch(Exception ex)
// catch the exception and prints the error if cannot find file
{
System.out.println("cannot find file ");
}
}
}
If you provide me correct it will be much easier to understand.

This code will not win prices, due to missing java expertice. For instance I would expect OutOfMemory even if it is correct.
Best would be a rewrite. Nevertheless we all began small.
Give full path to file. Also on the output the directory is probably missing from the file.
Better use BufferedReader etc. i.o. DateInputStream.
Initialize i with -1. Better use for (int i = 0; i < a.length; ++i).
Best compile the Pattern outside the loop. But remove the Matcher. You can do if (s.contains(">") as well.
. One does not need to create a new file.
Code:
const String encoding = "Windows-1252"; // Or "UTF-8" or leave away.
File f = new File("C:/input.txt");
BufferedReader dis = new BufferedReader(new InputStreamReader(
new FileInputStream(f), encoding));
...
int i= -1; // So i++ starts with 0.
while ((inputline=dis.readLine()) != null)
{
i++;
a[i]=inputline.trim();
//replaces unwanted patterns like /n with space
// Not needed a[i]=a[i].replaceAll(separator,"");

Your code contains the following two catch blocks:
catch(Exception e)
{
System.out.println("cannot open a file");
}
catch(Exception ex)
// catch the exception and prints the error if cannot find file
{
System.out.println("cannot find file ");
}
Both of these swallow the exception and print a generic "it didn't work" message, which tells you that the catch block was entered, but nothing more than that.
Exceptions often contain useful information that would help you track down where the real problem is. By ignoring them, you're making it much harder to diagnose your problem. Worse still, you're catching Exception, which is the superclass of a lot of exceptions, so these catch blocks are catching lots of different types of exceptions and ignoring them all.
The simplest way to get information out of an exception is to call its printStackTrace() method, which prints the exception type, exception message and stack trace. Add a call to this within both of these catch blocks, and that will help you see more clearly what exception is being thrown and from where.

How to erase existing text in a file

I'm working on an assignment for school, and am trying something beyond for extra credit. The program is to demonstrate the efficiency differences between a linear & binary search for a given array size of integers. I have a loop set up that creates an int[size] array, searches for a random number, then creates a new array of int[size*2].
The results are then written to a text file. The output writes fine, but after compiling & running the program several times, the output file has that many sections of data.
This is my code that is nested inside a try/catch block:
File output= new File("c:\\BigOhResults.txt");
int counter=2;
if (output.canWrite() && output.exists()) {
BufferedWriter out= new BufferedWriter(new FileWriter(output, true));
out.write(type+" \n\n"); //writes the search type
out.write(type+"Search Results\n\n");
while (counter <= data.size()) {
out.write(data.get(counter-1)+" millisecond runtime " +
"for a "+ data.get(counter-2)+" random number " +"sample size\n");
counter=counter+2;
}
}
Is there any way I can erase the text within that output file upon each time the program is run?
the reason I'm doing this is the professor requires the result printout with the data graphed. I have already completed the graphing requirement, and it works fine. I just want to have the file printout match the graph printout.

The second argument to the FileWriter constructor, which you're passing in "true", is "append". I.e. because you've set it to true, it will append your new output to the end of the file. If you pass in false instead, it will wipe the data that's there already and write it new.

Read the documentation for FileWriter. You do not want to append.

As already mentioned, the [FileWriter][1] constructor allows you to specify to clear the existing text and start at the beginning of the file. Some other remarks about the code:
The check on output.exists() is redundant after a call to output.canWrite() and isn't needed. output.canWrite() will check if the file exists and that you can write to it.
Don't forget to close the BufferedWriter object.
Like so:
if (output.canWrite()) {
BufferedWriter out = null;
try {
out = new BufferedWriter(new FileWriter(output, false));
out.write(type+" \n\n"); //writes the search type
out.write(type+"Search Results\n\n");
while (counter <= data.size()) {
out.write(data.get(counter-1)+" millisecond runtime " +
"for a "+ data.get(counter-2)+" random number " +"sample size\n");
counter=counter+2;
}
} catch (IOException e) {
// Do what you want here, print a message or something
} finally {
if(out != null) {
try {
out.close();
} catch (IOException e) {
// Again, do what you want here
}
}
}
}
[1]: http://java.sun.com/j2se/1.4.2/docs/api/java/io/FileWriter.html#FileWriter(java.io.File, boolean)

Okay so I tried something and it worked. This is when you have a file that is intended to append any new text, but you want to reset/erase the contents of the file at the beginning of program execution. Hope I made sense.
PrintWriter pw1 = new PrintWriter(new BufferedWriter(new FileWriter("newfile.txt")));
pw1.close(); // Make sure the first PrintWriter object name is different from the second one.
PrintWriter pw = new PrintWriter(new BufferedWriter(new FileWriter("newfile.txt", true))); // PrintWriter in append-mode. When you recreate the text file with the same name, the file contents are erased because the previous object was not in append mode.
pw.close();