I asked a similar question before regarding I/O using Java.
I'm trying to copy a list of strings into another file.
package file;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
public class File {
public static void main(String[] args) {
FileWrite fW = new FileWrite();
try (BufferedReader br = new BufferedReader(new FileReader("B:\\inLarge.dat")))
{
String stCurrent;
while ((stCurrent = br.readLine()) != null) {
System.out.println(stCurrent);
fW.serializeAddress(stCurrent, stCurrent);
}
} catch (IOException e) {
e.printStackTrace();
}
//fW.serializeAddress("Boston", "Canada");
}
}
And
package file;
import java.io.BufferedWriter;
import java.io.FileOutputStream;
import java.io.FileWriter;
import java.io.ObjectOutputStream;
import java.io.PrintStream;
import java.io.Serializable;
import java.io.File;
import java.io.IOException;
public class FileWrite {
public void serializeAddress(String city, String country){
try
{
File file = new File("B:\\outLarge.txt");
if (!file.exists())
{
file.createNewFile();
}
FileWriter fw = new FileWriter(file.getAbsoluteFile());
BufferedWriter bw = new BufferedWriter(fw);
bw.write(city + " " + country);
bw.close();
System.out.println("Done");
}
catch(Exception ex)
{
ex.printStackTrace();
}
}
}
But the ending output file has only one result, how do I make it copy everything?
I am thinking buffered-writer somehow needs to be in the loop to write new ones on top of existing ones? But not sure how to implement that.
Thanks a lot.
You are overwriting the file contents every time you call your serialize method, because you didn't open the file in append mode. To prevent overwriting, open the file in append mode:
FileWriter fw = new FileWriter(file.getAbsoluteFile(), true);
However, this is one case where the solution is probably over-engineered. For efficiency you really should be opening your file just once. Here's an example:
public static void main(final String[] args) {
try {
final BufferedReader reader = new BufferedReader(new FileReader("infile.txt"));
final PrintWriter writer = new PrintWriter(new File("outfile.txt"));
String inputLine;
while((inputLine = reader.readLine()) != null) {
writer.println(inputLine);
}
reader.close();
writer.close();
} catch(final Exception e) {
e.printStackTrace();
}
}
You're overwriting the existing file every time you open it. Instead append to it.
Change
FileWriter fw = new FileWriter(file.getAbsoluteFile());
to
FileWriter fw = new FileWriter(file.getAbsoluteFile(), true);
Related
I'm trying to introduce a line break at every 100th character of the line from the existing file.But it doesn't write anything to it. below is the code written in java to read the existing file and write to it with a temporary file.
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
public class ReplaceFileContents {
public static void main(String[] args) {
new ReplaceFileContents().replace();
}
public void replace() {
String oldFileName = "Changed1.ldif";
String tmpFileName = "Changed2.ldif";
BufferedReader br = null;
BufferedWriter bw = null;
try {
br = new BufferedReader(new FileReader(oldFileName));
bw = new BufferedWriter(new FileWriter(tmpFileName));
String line;
while ((line = br.readLine()) != null) {
line.replaceAll("(.{100})", "$1\n");
}
} catch (Exception e) {
return;
} finally {
try {
if(br != null)
br.close();
} catch (IOException e) {
//
}
try {
if(bw != null)
bw.close();
} catch (IOException e) {
//
}
}
// Once everything is complete, delete old file..
File oldFile = new File(oldFileName);
oldFile.delete();
// And rename tmp file's name to old file name
File newFile = new File(tmpFileName);
newFile.renameTo(oldFile);
}
}
while ((line = br.readLine()) != null) {
line.replaceAll("(.{100})", "$1\n");
}
First off, line.replaceAll does not replace your line variable with the result. Because Strings are immutable, this method returns the new string, so your line should be line = line.replaceAll(....
Second, you're never writing the new String back into the file. Using replaceAll doesn't change the file itself in any way. Instead, try using your bw object to write the new String to the same line.
From what you've published here, you never try to write line back to bw. Try this:
package hello;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
public class Test {
public static void main(String[] args) {
new Test().replace();
}
public void replace() {
String oldFileName = "d:\\1.txt";
String tmpFileName = "d:\\2.txt";
BufferedReader br = null;
BufferedWriter bw = null;
try {
br = new BufferedReader(new FileReader(oldFileName));
bw = new BufferedWriter(new FileWriter(tmpFileName));
String line;
while ((line = br.readLine()) != null) {
line = line.replaceAll("(.{100})", "$1\n");
bw.write(line);
}
} catch (Exception e) {
return;
} finally {
try {
if(br != null)
br.close();
} catch (IOException e) {
//
}
try {
if(bw != null)
bw.close();
} catch (IOException e) {
//
}
}
// Once everything is complete, delete old file..
File oldFile = new File(oldFileName);
oldFile.delete();
// And rename tmp file's name to old file name
File newFile = new File(tmpFileName);
newFile.renameTo(oldFile);
}
}
You never try to write line back to bw;
String#replaceAll will return the copy of the source not the original String;
I am out of ideas, I've been trying for the whole day to separate one file which has a format of :
AN Aixas
AN Aixirivall
AN Aixovall
AN Andorra la Vella
BR Salto do Mandira
BR Salto do Norte
BR Salto Dollman
BR Salto Grande
BR Salto Pilao
...
and so one, into different files by the name of the Country "AA.txt" and to include all the cities in these separate files. But my program only writes to a certain bunch of files and I cannot figure out why.
I've tried all the writing files classes - same result.
Here is the result, all worked but on a certain bunch of files only.
Here is the code :
package com.fileorganizer;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
public class File2 implements Cloneable {
static InputStream fis = null;
static BufferedReader br = null;
static String state = "";
static String tmp = "";
static File file = null;
static FileWriter fw = null;
static BufferedWriter bw = null;
public static void main(String[] args) {
int a = 0;
try {
fis = new FileInputStream(
new File(
"/Users/Mihail/Documents/WorkSpace/Parse-Starter-Project-1.8.2/ParseStarterProject/res/raw/cities.txt"));
br = new BufferedReader(new InputStreamReader(fis));
String line = null;
while ((line = br.readLine()) != null) {
state = line.substring(0, 2);
if (state.substring(0, 1).matches("^[A-Z]+$")
&& state.substring(1, 2).matches("^[A-Z]+$")
&& !tmp.equals(state)) {
file = new File(
"/Users/Mihail/Documents/WorkSpace/Parse-Starter-Project-1.8.2/ParseStarterProject/res/raw/countriesFolder/"
+ state + ".txt");
fw = new FileWriter(file.getAbsoluteFile());
bw = new BufferedWriter(fw);
tmp = state;
}
bw.write(line.substring(3) + "\n");
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if (br != null)
br.close();
} catch (Exception ex) {
}
}
}
}
I am really sorry for such a dumb question. Please help
You don't close bw anywhere, so the contents in the BufferedWriter's buffer are lost.
I have written a simple code to write text into file but i am not able to figure out why text is not written to file. I have written a class with method which will take text file as input and create the text file if it is not exist
here is the code:
import java.io.File;
import java.io.FileOutputStream;
import java.io.FileWriter;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.UnsupportedEncodingException;
public class OutputFile {
public static BufferedWriter fbw = null;
public BufferedWriter createFile(String text)
{
try{
File file =new File(text);
if(!file.exists()){
file.createNewFile();
}
FileWriter writer = new FileWriter(text,true);
fbw =new BufferedWriter(writer);
}
catch (IOException e)
{
System.out.println(e.getMessage());
}
return fbw;
}
public static void main(String args[]) throws IOException
{
String resultFilePath = "C:/Users/Desktop/stringcompare/output.txt";
OutputFile file = new OutputFile();
fbw = file.createFile(resultFilePath);
fbw.write("hello");
fbw.newLine();
fbw.close();
}
}
Try this:
try(BufferedWriter bw = new BufferedWriter(new FileWriter("FILE_PATH_HERE"))){
br.write("STUFF_TO_WRITE_HERE");
} catch(IOException e){
}
With this try-with-resources statement, all of the closing file effort is done automatically.
This will only work for Java 7 or higher.
You have to flush your output. This can be done directly by calling writer.flush().
In my below code I wanted to replace the text "DEMO" with "Demographics" but instead of replacing the text it deletes the entire content of the text file.
Contents inside the file:
DEMO
data
morning
PS: I'm a beginner in java
package com.replace.main;
import java.io.*;
public class FileEdit {
public static void main(String[] args) {
BufferedReader br = null;
BufferedWriter bw = null;
String readLine, replacedData;
try {
bw = new BufferedWriter(
new FileWriter(
"Demg.ctl"));
br = new BufferedReader(
new FileReader(
"Demg.ctl"));
System.out.println(br.readLine()); //I Get Null Printed Here
while ((readLine = br.readLine())!= null) {
System.out.println("Inside While Loop");
System.out.println(readLine);
if (readLine.equals("DEMO")) {
System.out.println("Inside if loop");
replacedData = readLine.replaceAll("DEMO","Demographics");
}
}
System.out.println("After While");
br.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
You open a Writer to your file, but you don't write anything. This means that your file is replaced with an empty file.
Besides this you also need to close your writer, not just the reader.
And last but not least, your if condition is wrong.
if (readLine.equals("DEMO")) {
should read
if (readLine.contains("DEMO")) {
Otherwise it would only return true if your line contained "DEMO" but nothing else.
I'm updating the answer to my own question.
package com.replace.main;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
public class FileEdit
{
public static void main(String args[])
{
try
{
BufferedReader reader = new BufferedReader(new FileReader("Demg.ctl"));
String readLine = "";
String oldtext = "";
while((readLine = reader.readLine()) != null)
{
oldtext += readLine + "\r\n";
}
reader.close();
// To replace the text
String newtext = oldtext.replaceAll("DEMO", "Demographics");
FileWriter writer = new FileWriter("Demg.ctl");
writer.write(newtext);
writer.close();
}
catch (IOException e)
{
e.printStackTrace();
}
}
}
I have used the functions oldFile.delete() and newfile.rename("oldFile.txt") both are file object but this is not working, delete function and rename function gives an error,
the source code is below:
package urlFiltering;
import java.io.*;
import java.net.InetAddress;
public class mainForm{
public static void main(String args[]) throws IOException {
String hostName="www.stackoverflow.com";
InetAddress inetAddress=InetAddress.getByName(hostName);
String host=inetAddress.toString();
FileReader inputFile = new FileReader("StoredIp.txt");
File tempFile= new File("tempFile.txt");
BufferedReader bufferReader = new BufferedReader(inputFile);
String line;
while ((line = bufferReader.readLine()) != null) {
if(host.equals(line))
continue;
else
{
if (!tempFile.exists()) {
tempFile.createNewFile();
}
FileWriter fw = new FileWriter(tempFile,true);
BufferedWriter bw = new BufferedWriter(fw);
bw.write(line);
bw.newLine();
bw.close();
}
}
bufferReader.close();
inputFile.delete();//error
tempFile.renameTo("StoredIp.txt"); //error
}
}
Your inputFile is a FileReader, which doesn't have a delete() method. You can create a File object to represent that file, and give that File as input to the FileReader constructor. Then you can also invoke the delete() method on the File object at the end, instead of on the FileReader. The renameTo() gives you an error because the method expects a File and not a String. Do renameTo(new File("StoredIp.txt")) for it instead. In other words, this:
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.net.InetAddress;
public class mainForm {
public static void main(String args[]) throws IOException {
String hostName = "www.stackoverflow.com";
InetAddress inetAddress = InetAddress.getByName(hostName);
String host = inetAddress.toString();
File inputF = new File("StoredIp.txt");
FileReader inputFile = new FileReader(inputF);
File tempFile = new File("tempFile.txt");
BufferedReader bufferReader = new BufferedReader(inputFile);
String line;
while ((line = bufferReader.readLine()) != null) {
if (host.equals(line))
continue;
else {
if (!tempFile.exists()) {
tempFile.createNewFile();
}
FileWriter fw = new FileWriter(tempFile, true);
BufferedWriter bw = new BufferedWriter(fw);
bw.write(line);
bw.newLine();
bw.close();
}
}
bufferReader.close();
inputF.delete();// no more error
tempFile.renameTo(new File("StoredIp.txt")); // no more error
}
}