I am trying to read lines from a file. For this, I am using the following code:
try {
String line;
try (InputStream fis = new FileInputStream("AbsoluteFilePath");
InputStreamReader isr = new InputStreamReader(fis, Charset.forName("Cp1252"));
BufferedReader br = new BufferedReader(isr);) {
FactGeneration.getFacts();
while ((line = br.readLine()) != null) {
br.readLine();
function1(line);
However, this does not move to the next line in the file.
Thank you!
Edit:
For clarity, I am making a twitter bot. The entire function looks like this:
FactGeneration.getFacts() appends a new line to the file located at /AbsoluteFilePath
private static void tweetLines() {
String tweet;
int count = 0;
while (count < 10) {
try {
try (InputStream fis = new FileInputStream(
"/AbsoluteFilePath");
InputStreamReader isr = new InputStreamReader(fis, Charset.forName("Cp1252"));
BufferedReader br = new BufferedReader(isr);) {
FactGeneration.getFacts();
while ((tweet = br.readLine()) != null) {
sendTweet(tweet);
try {
int sleepTime = 18000;
Thread.sleep(sleepTime);
}
catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
catch (IOException e) {
e.printStackTrace();
}
count += 1;
}
}
Edit:
The following is the working code:
while (count < numTweets) {
try {
try (InputStream fis = new FileInputStream(fileName);
InputStreamReader isr = new InputStreamReader(fis, Charset.forName("Cp1252"));
BufferedReader br = new BufferedReader(isr)) {
//Calls static method GetFacts from the FactGeneration class.
FactGeneration.getFacts();
tweet = br.readLine();
while (tweet != null) {
//sendTweet accesses the TwitterAPI and posts the tweet.
sendTweet(tweet);
System.out.println("tweeting:" + tweet);
try {
//Pauses the thread for the given amount of time.
int sleepTime = 18000; //in milliseconds.
System.out.printf("Sleeping for %d seconds", sleepTime / 1000);
Thread.sleep(sleepTime);
}
catch (InterruptedException e) {
e.printStackTrace();
}
//moves to the next line in the file.
tweet = br.readLine();
}
}
}
catch (IOException e) {
e.printStackTrace();
}
count += 1;
if (count == numTweets) {
System.out.println("Tweet limit reached");
}
}
The readLine actually reads a line, it does it inside the condition of the while loop, so don't read a second time inside the loop
String line;
try (InputStream fis = new FileInputStream("AbsoluteFilePath");
InputStreamReader isr = new InputStreamReader(fis, Charset.forName("Cp1252"));
BufferedReader br = new BufferedReader(isr);) {
while ((line = br.readLine()) != null) {
// do whatever with line
}
}
The while condition has 2 steps, this allows, that at the end, it reads null and stop looping
read a line from the file and assign the result to line
check that line is not null
Related
I have a simulation program that needs to write certain results to a csv file very frequently during execution. I have found that there is something wrong with the printwriter which dramatically slows down running my program, as the output file is getting larger in size (near to 1 million rows). I doublt it's overwriting the entire file each time from the beginning, wheras I just need to append a single line at the bottom each time when it's being called. below is the code related to the writing fuctions.
one of the writing fuctions:
public void printHubSummary(Hub hub, String filePath) {
try {
StringBuilder sb = new StringBuilder();
String h = hub.getHub_code();
String date = Integer.toString(hub.getGs().getDate());
String time = hub.getGs().getHHMMFromMinute(hub.getGs().getClock());
String wgt = Double.toString(hub.getIb_wgt());
sb.append(h+","+date+","+time+","+wgt);
// System.out.println("truck print line: " + sb);
FileWriter.writeFile(sb.toString(),filePath);
}
catch (Exception e) {
System.out.println("Something wrong when outputing truck summary file!");
e.printStackTrace();
}
}
the file writer code: (should be where the problem is!)
public static boolean writeFile(String newStr, String filename) throws IOException {
boolean flag = false;
String filein = newStr + "\r\n";
String temp = "";
FileInputStream fis = null;
InputStreamReader isr = null;
BufferedReader br = null;
FileOutputStream fos = null;
PrintWriter pw = null;
try {
File file = new File(filename);
fis = new FileInputStream(file);
isr = new InputStreamReader(fis);
br = new BufferedReader(isr);
StringBuffer buf = new StringBuffer();
for (int j = 1; (temp = br.readLine()) != null; j++) {
buf = buf.append(temp);
buf = buf.append(System.getProperty("line.separator"));
}
if (buf.length() > 0 && buf.charAt(0) == '\uFEFF') {
buf.deleteCharAt(0);
}
buf.append(filein);
fos = new FileOutputStream(file);
byte[] unicode = {(byte)0xEF, (byte)0xBB, (byte)0xBF};
fos.write(unicode);
pw = new PrintWriter(fos);
pw.write(buf.toString().toCharArray());
pw.flush();
flag = true;
} catch (IOException e1) {
throw e1;
} finally {
if (pw != null) {
pw.close();
}
if (fos != null) {
fos.close();
}
if (br != null) {
br.close();
}
if (isr != null) {
isr.close();
}
if (fis != null) {
fis.close();
}
}
return flag;
}
An update on code modification. I have freezed the operations of repeatitively overwrting the entire file. It appears to solve the problem, but writing for sometime it's slowed down as well. Is it the best arrangement for wrting very large file? what other modifications can be done to make it even more efficient?
public static boolean writeFile1(String newStr, String filename) throws IOException {
boolean flag = false;
String filein = newStr + "\r\n";
String temp = "";
FileInputStream fis = null;
InputStreamReader isr = null;
BufferedReader br = null;
FileOutputStream fos = null;
PrintWriter pw = null;
try {
File file = new File(filename);
fis = new FileInputStream(file);
isr = new InputStreamReader(fis);
br = new BufferedReader(isr);
StringBuffer buf = new StringBuffer();
// for (int j = 1; (temp = br.readLine()) != null; j++) {
// buf = buf.append(temp);
// buf = buf.append(System.getProperty("line.separator"));
// }
// if (buf.length() > 0 && buf.charAt(0) == '\uFEFF') {
// buf.deleteCharAt(0);
// }
buf.append(filein);
fos = new FileOutputStream(file,true);
byte[] unicode = {(byte)0xEF, (byte)0xBB, (byte)0xBF};
fos.write(unicode);
pw = new PrintWriter(fos);
pw.write(buf.toString().toCharArray());
pw.flush();
flag = true;
} catch (IOException e1) {
throw e1;
} finally {
if (pw != null) {
pw.close();
}
if (fos != null) {
fos.close();
}
if (br != null) {
br.close();
}
if (isr != null) {
isr.close();
}
if (fis != null) {
fis.close();
}
}
return flag;
}
Provide a second argument to the FileOutputStream constructor to specify whether or not to use append mode, which will add to the end of the file rather than overwriting it.
fos = new FileOutputStream(file, true);
Alternatively, you could create a single static PrintWriter in append mode, which will probably be faster as it reduces garbage collection.
Use the Files / Path / Java NIO2 which is richer: the code below would need Java 7 at least.
Path path = Paths.get(filename);
try (BufferedWriter bw = Files.newBufferedWriter(
path, StandardCharsets.UTF_8, StandardOpenOption.APPEND, StandardOpenOption.CREATE, StandardOpenOption.WRITE)) {
bw.append(filein);
bw.newLine();
}
Your cue here is the StandardOpenOption.
You will probably have to do some additional code before to write the Unicode part (and fix the StandardCharsets.UTF_8):
if (Files.notExists(path)) {
Files.write(path, new byte[] {(byte)0xEF, (byte)0xBB, (byte)0xBF});
}
Also, try to not use StringBuffer in a local method, use StringBuilder: you don't need synchronisation most of the time.
I have a file with say 20 lines. I need to read first 3 lines, process it and write it to another file. Then give a delay of 62 seconds, read the next 3 lines and so on till the nth line. How do I go about it?. I was successful in writing first 3 lines, but confused where to put the loop for another iteration.
FileInputStream fis = new FileInputStream("C:\\Users\\Rao\\Desktop\\test.txt");
br = new BufferedReader(new InputStreamReader(fis, "UTF-8"));
String sCurrentLine;
int counter = 0;
while ((sCurrentLine = br.readLine()) != null) {
if (counter < 3) {
URL oracle = new URL("http://ip-api.com/json/"+sCurrentLine+"?"+"fields=isp");
BufferedReader in = new BufferedReader(new InputStreamReader(oracle.openStream()));
String inputLine;
while ((inputLine = in.readLine()) != null) {
String baby= (sCurrentLine+ "\t"+ inputLine);
try {
FileWriter writer = new FileWriter("C:\\Users\\Rao\\Desktop\\output.txt", true);
writer.write(baby);
writer.write("\r\n"); // write new line
writer.close();
} catch (IOException e) {
e.printStackTrace();
}
} in.close();
}
counter++; }
TimeUnit.SECONDS.sleep(62); }
finally {
if (br != null) br.close();
}
}
}
try this. So it will sleep every third attempt.
while ((sCurrentLine = br.readLine()) != null) {
// process the data which you have read.
if ((counter % 3) == 0 ) {
TimeUnit.SECONDS.sleep(62);
}
}
My Code to get file content:
private String readTxt(){
InputStream inputStream = getResources().openRawResource(R.raw.text);
ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
int i;
try {
i = inputStream.read();
while (i != -1)
{
byteArrayOutputStream.write(i);
i = inputStream.read();
}
inputStream.close();
}
catch (IOException e)
{
e.printStackTrace();
}
return byteArrayOutputStream.toString();
}
but i want only one specific line on that file to be extracted.
Use BufferedReader instead of ByteArrayOutputStream.
String readLine(int line) throws IOException {
InputStream in = getResources().openRawResource(R.raw.text);
BufferedReader r = new BufferedReader(new InputStreamReader(in));
try {
String lineStr = null;
int currentLine = 0;
while ((lineStr = r.readLine()) != null) {
if (currentLine++ == line) {
return lineStr;
}
}
} finally {
if (r != null) {
r.close();
}
}
throw new IOException("line " + line + " not found");
}
I'm working on a project for school, where I want to load questions from a file. However, Java is unable to load the file. I am sure the text file is named right and in the right direactory, but here they are:
game>src
game>out>production>game
private static void init(){
BufferedReader br = null;
ArrayList<String> strings= new ArrayList<String>();
try {
String sCurrentLine;
br = new BufferedReader(new FileReader(new File("questions.txt")));
while ((sCurrentLine = br.readLine()) != null) {
strings.add(sCurrentLine);
}
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if (br != null)br.close();
} catch (IOException ex) {
ex.printStackTrace();
}
}
int i = 0;
while(i < strings.size()){
String text = strings.get(i++);
int numAnswers = Integer.parseInt(strings.get(i++));
ArrayList<String> answers = new ArrayList<String>();
for (int i2 = 0; i2 < numAnswers; i2++){
answers.add(strings.get(i++));
}
questions.add(new Question(text, answers));
}
}
Try scr/questions.txt as path.
br = new BufferedReader(new FileReader(new File("src/questions.txt")));
Can anyone point me in the right direction here. I have a method that is supposed to read a file and display the data in that file. I can only get it to display one line. I know it is something simple I am over looking, but my brain is mush and I just keep digging a bigger hole.
public static String readFile(String file) {
String data = "";
if (!new java.io.File(file).exists()) {
return data;
}
File f = new File(file);
FileInputStream fStream = null;
BufferedInputStream bStream = null;
BufferedReader bReader = null;
StringBuffer buff = new StringBuffer();
try {
fStream = new FileInputStream(f);
bStream = new BufferedInputStream(fStream);
bReader = new BufferedReader(new InputStreamReader(bStream));
String line = "";
while (bStream.available() != 0) {
line = bReader.readLine();
if (line.length() > 0) {
if (line.contains("<br/>")) {
line = line.replaceAll("<br/>", " ");
String tempLine = "";
while ((tempLine.trim().length() < 1)
&& bStream.available() != 0) {
tempLine = bReader.readLine();
}
line = line + tempLine;
}
buff.append(line + "\n");
}
}
fStream.close();
bStream.close();
bReader.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return buff.toString();
}
String line = null;
while ((line = bReader.readLine())!=null)
How about doing this with Guava:
http://docs.guava-libraries.googlecode.com/git/javadoc/com/google/common/io/Files.html
List<String> lines = Files.readLines("myFile.txt", Charset.forName("UTF-8"));
System.out.println(lines);
You'd still have to do a little bit of work to concatenate the <br> lines etc...