I am using a buffered reader to read in a file filled with lines of information. Some of the longer lines of text extend to be more than one line so the buffered views them as a new line. Each line ends with ';' symbol. So I was wondering if there was a way to make the buffered reader read a line until it reaches the ';' then return the whole line as a string. Here a how I am using the buffered reader so far.
String currentLine;
while((currentLine = reader.readLine()) != null) {
// trim newline when comparing with lineToRemove
String[] line = currentLine.split(" ");
String fir = line[1];
String las = line[2];
for(int c = 0; c < players.size(); c++){
if(players.get(c).getFirst().equals(fir) && players.get(c).getLast().equals(las) ){
System.out.println(fir + " " + las);
String text2 = currentLine.replaceAll("[.*?]", ".150");
writer.write(text2 + System.getProperty("line.separator"));
}
}
}
It would be much easier to do with a Scanner, where you can just set the delimiter:
Scanner scan = new Scanner(new File("/path/to/file.txt"));
scan.useDelimiter(Pattern.compile(";"));
while (scan.hasNext()) {
String logicalLine = scan.next();
// rest of your logic
}
To answer your question directly, it is not possible. Buffered Reader cannot scan stream in advance to find this character and then return everything before target character.
When you read from stream with Buffered Reader you are consuming characters and you cannot really know character without reading.
You could use inherited method read() to read only single character and then stop when you detect desired character. Granted, this is not good thing to do because it contradicts the purpose of BufferedReader.
Related
i have a question. I have a text file with some names and numbers arranged like this :
Cheese;10;12
Borat;99;55
I want to read the chars and integers from the file until the ";" symbol, println them, then continue, read the next one, println etc. Like this :
Cheese -> println , 10-> println, 99 -> println , and on to the next line and continue.
I tried using :
BufferedReader flux_in = new BufferedReader (
new InputStreamReader (
new FileInputStream ("D:\\test.txt")));
while ((line = flux_in.readLine())!=null &&
line.contains(terminator)==true)
{
text = line;
System.out.println(String.valueOf(text));
}
But it reads the entire line, doesn`t stop at the ";" symbol. Setting the 'contains' condition to false does not read the line at all.
EDIT : Partially solved, i managed to write this code :
StringBuilder sb = new StringBuilder();
// while ((line = flux_in.readLine())!=null)
int c;
String terminator_char = ";";
while((c = flux_in.read()) != -1) {
{
char character = (char) c;
if (String.valueOf(character).contains(terminator_char)==false)
{
// System.out.println(String.valueOf(character) + " : Char");
sb.append(character);
}
else
{
continue;
}
}
}
System.out.println(String.valueOf(sb) );
Which returns a new string formed out of the characters from the read one, but without the ";". Still need a way to make it stop on the first ";", println the string and continue.
This simple code does the trick, thanks to Stefan Vasilica for the ideea :
Scanner scan = new Scanner(new File("D:\\testfile.txt"));
// Printing the delimiter used
scan.useDelimiter(";");
System.out.println("Delimiter:" + scan.delimiter());
// Printing the tokenized Strings
while (scan.hasNext()) {
System.out.println(scan.next());
}
// closing the scanner stream
scan.close();
Read the characters from file 1 by 1
Delete the 'contains' condition
Use a stringBuilder() to build yourself the strings 1 by 1
Each stringBuilder stops when facing a ';' (say you use an if clause)
I didn't test it because I'm on my phone. Hope this helps
I am writing a class that will read lines from a log file when it is updated.
I am using Apache VFS2 to get a method called when a file is updated. My main issue is I don't want to read the line from the file if the line is not complete yet, as in it does have a "\n" or "\r" line separator type character at the end. I think i have looked at all the Java libraries i can to read lines but they all discard the EOF and line termination information so I don't think I can use them.
Instead I am looking at reading it in byte by byte and then checking the result to then discard all stuff that comes after the last line separator. I was wondering what you folks thoughts on the best method for doing this is.
So for example:
2013-Jul-01_14:07:17.875 - Connection to Message Bus is reestablished<LF>
2013-Jul-01_14:07:17.875 - Connection to Message Bus is reestablished<LF>
2013-Jul-01_14:15:08.205 - No connection to Message Bus - reestablish before we can publish<LF>
2013-Jul-01_14:15:08.205 - NOT A REAL LINE PLEASE DONT READ
I want to read in the first 3 but not the fourth as it doesn't have a line feed or carriage return character ().
I have looked at Apache commons-io Tailer stuff but I cant tell if that will give me "incomplete" lines (and I realize I will have to ditch the VFS2 stuff to use it).
So psudo-code:
private void ingestFileObject(FileObject file) {
BufferedInputStream bs = new BufferedInputStream(file.getContent().getInputStream());
StringBuilder result = new StringBuilder();
while (bs.available() > 0) {
result.append((char) bs.read());
}
bs.close();
String resultString = result.toString();
//determine what part of resultString is after last carriage return/line seperate (using regex [\\r\\n]+?
//remove the offending part of String.
}
Or any other solutions completely ignoring my psudo-code are welcome at this point too...
Thanks
Is using Scanner help you?
Scanner scanner = new Scanner(file);
//block till there is some thing with a new line
while (scanner.hasNextLine()) {
String line = scanner.nextLine();
//do processing.
}
This is what I ended up doing:
BufferedReader bufReader = new BufferedReader(new InputStreamReader(file.getContent().getInputStream()));
StringBuilder result = new StringBuilder();
int readInInt = -1;
String charsSinceLastLineSep = "";
if (bufReader.ready()) {
while (-1 != (readInInt = bufReader.read())) {
char readInChar = (char) readInInt;
// if new line reset line buffer, otherwise add to buffer
if (readInChar == '\n' || readInChar == '\r') {
charsSinceLastLineSep = "";
} else {
charsSinceLastLineSep += readInChar;
}
result.append(readInChar);
}
bufReader.close();
// remove all characters added since last Carriage Return or NewLine was found indicating
// that line was not a complete log line
String resultString = (result.subSequence(0, (result.length() - charsSinceLastLineSep.length())).toString());
I want to read strings from a file. When a certain string (><) is found, I want to start reading integers instead, and convert them to binary strings.
My program is reading the strings in and saving them in an ArrayList successfully, but
it does not recognise the >< symbol and therefore the reading of the binary strings is not successful.
The Code
try {
FileInputStream fstream = new FileInputStream(fc.getSelectedFile().getPath());
// Get the object of DataInputStream
DataInputStream ino = new DataInputStream(fstream);
BufferedReader br = new BufferedReader(new InputStreamReader(ino));
String ln;
String str, next;
int line, c =0;
while ((ln = br.readLine()) != null) {
character = ln;
System.out.println(character);
iname.add(ln); // arraylist that holds the strings
if (iname.get(c).equals("><")) {
break; // break and moves
// on with the following while loop to start reading binary strings instead.
}
c++;
}
String s = "";
// System.out.println("SEQUENCE of bytes");
while ((line = ino.read()) != -1) {
String temp = Integer.toString(line, 2);
arrayl.add(temp);
System.out.println("telise? oxii");
System.out.println(line);
}
ino.close();
} catch (Exception exc) { }
The file I'm trying to read is for example:
T
E
a
v
X
L
A
.
x
"><"
sequence of bytes.
Where the last part is saved as bytes and in the textfile appears like that. no worries this bit works. all the strings are saved in a new line.
< is two characters and iname.get(c) is only one character.
What u should do is test if ln equals > and then another test if the next character equals < . If both test pass then break out of the loop.
you will have to becarefull
Use a Scanner. It allows you to specify a delimiter, and has methods for reading input tokens as String or int.
Could you not do something like:
while ((ln = br.readLine()) != null){
character=ln;
System.out.println(character);
//
// Look for magic characters >< and stop reading if found
//
if (character.indexOf("><") >= 0) {
break;
}
iname.add(ln);
}
This would work if you didn't want to add the magic symbol to your ArrayList. Your code sample is incomplete - if you're still having trouble you'd need to post the whole class.
I am writing a small java app which will scan a text file for any instances of particular word and need to have a feature whereby it can report that an instance of the word was found to be the 14th word in the file, on the third line, for example.
For this i tried to use the following code which i thought would check to see whether or not the input was a newline (\n) character and then incerement a line variable that i created:
FileInputStream fileStream = new FileInputStream("src/file.txt");
DataInputStream dataStream = new DataInputStream(fileStream);
BufferedReader buffRead = new BufferedReader(new InputStreamReader(dataStream));
String strLine;
String Sysnewline = System.getProperty("line.separator");
CharSequence newLines = Sysnewline;
int lines = 1;
while ((strLine = buffRead.readLine()) != null)
{
if(strLine.contains(newLines))
{
System.out.println("Line Found");
lines++;
}
}
System.out.println("Total Number Of Lines In File: " + lines);
This does not work for, it simply display 0 at the end of this file. I know the data is being placed into strLine during the while loop as if i change the code slightly to output the line, it is successfully getting each line from the file.
Would anyone happen to know the reason why the above code does not work?
Read the javadocs for readLine.
Returns:
A String containing the contents of the line, not including any line-termination characters, or null if the end of the stream has been reached
readLine() strips newlines. Just increment every iteration of the loop. Also, you're overcomplicating your file reading code. Just do new BufferedReader(new FileReader("src/file.txt"))
I'm having some problems with the FileReader class.
How do I specify an offset in the lines it goes through, and how do I tell it when to stop?
Let's say I want it to go through each line in a .txt file, but only lines 100-200 and then stop?
How would I do this? Right now I'm using ReadLine() but I don't think there's a way to specify offset with that.
Any fast help is VERY appreciated. Thanks.
You can't. FileReader reads a character at a time or a line at a time. Obviously you can write your own code extending or wrapping it to skip to the unneeded lines.
An aside: Be CAREFUL using FileReader or FileWriter - they use the default LOCALE character set. If you want to force a character set use OutputStreamWriter or InputStreamReader. Example
Writer w = new FileWriter(file) can be replaced by
Writer w = new OutputStreamWriter(new FileOutputStream(file),"UTF-8"); <=== see how I can set the character set.
An alternative: If you have FIXED-WIDTH text, then look at RandomAccessFile which lets you seek to any position. This doesn't help you much unless you have fixed width text or an index to skip to a line. But it is handy :)
Read all the lines but use another variable to count which line you are on. Call continue if you are on a line that you don't want to process (say, before the 100th line) and break when you will not want to process any more lines (after the 200th line).
There is not a way to tell the reader to only read certain lines, you can just use a counter to do it.
try {
BufferedReader in = new BufferedReader(new FileReader("infilename"));
String str;
int lineNumber = 0;
while ((str = in.readLine()) != null) {
lineNumber++;
if (lineNumber >= 100 && lineNumber <= 200) {
System.out.println("Line " + lineNumber + ": " + str);
}
}
in.close();
} catch (IOException e) { }
BufferedReader in = new BufferedReader(new FileReader("foo.in"));
for(int i=0;i<100;i++,in.readLine()){}
String line101 = in.readLine();