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hello every one
how can I read a specific line in java for example line 7 in an input file I have used buffered reader but in this method I need to used line.nexline() and also I have used the LinenumberReader but in this method I can not give the line number I want to read
please help
thanks alot
In general you can't read the 7th line directlly. You need to create a loop to read the first 6 first.
However, if the length of each line is a "fixed length", then you can use RandomAccessFile and calculate the bytes to read manually at one time. I doubt you lines are fixed length so you will need to use the first solution.
You would need to read the lines before this line, and just ignore them or discard them, and for each line read, increment a counter, when the counter reaches the desired line, return that line, and of course checking to see if the file runs out before the requested line number has come up.
I used this post on sun forums to read a new line in a platform independent manner:Code:/**
* Reads a specific line from a text file in a platform neutral way, ignoring the lines before, and stopping after
* reaching the desired line.
*
* @param file
* The file to read from
* @param lineNumber
* the line number to read.
* @return the line that was requested, or null if the line number requested exceeds the number of lines in the file.
* @throws IOException
* if an error was encountered while trying to read the file
*/
public static String readSpecificLine(File file, int lineNumber) throws IOException {
StringBuilder lineBuffer = new StringBuilder();
String result = null;
int lineCount = 0; // used to read until the specific line has been found.
Reader reader = new InputStreamReader(new FileInputStream(file));
try {
char[] buffer = new char[4096];
outer: for (int charsRead = reader.read(buffer); charsRead >= 0; charsRead = reader.read(buffer)) {
for (int charIndex = 0; charIndex < charsRead; charIndex++) {
char aChar = buffer[charIndex];
switch (aChar) {
case '\r': // ignore DOS end of lines (that will be before \n)
break;
case '\n':
lineCount++;
if (lineCount == lineNumber) {
result = lineBuffer.toString();
break outer;
}
else {
// read a new line, but not interested in this line, discard
lineBuffer = new StringBuilder();
}
break;
default:
lineBuffer.append(aChar);
break;
} // switch
} // for (lineCount)
} // for ( reading the file )
}
finally {
try {
reader.close();
}
catch (IOException ex) {
// empty
}
}
return result;
}
Java Programming [Archive] - Fastest way to line count a file
thanks alot for the replies I though that there is a way to read a line directly but now I have used line.nextLine() to go to specific line
thanks alot
http://java.sun.com/javase/6/docs/ap...l/Scanner.html can be used for scanning and processing many kinds of text input from a variety of sources.
http://java.sun.com/javase/6/docs/ap...redReader.html allows for buffered reading from an input stream and has a readLine() method that will read a single line from a stream (file in your case).
String.split() http://java.sun.com/javase/6/docs/ap...va.lang.String) splits a string by the supplied expression and returns the pieces as an array of strings.
The following code fragment opens a BufferedReader against a text file and reads each line.
Help with Code Tags Java Syntax (Toggle Plain Text)
try { BufferedReader reader = new BufferedReader(new FileReader("file.txt")); String line = null; while ((line = reader.readLine()) != null){ System.out.println(line); } } catch (Exception e){ e.printStackTrace(); } try {
BufferedReader reader = new BufferedReader(new FileReader("<strong class="highlight">file</strong>.txt"));
String <strong class="highlight">line</strong> = null;
while ((<strong class="highlight">line</strong> = reader.readLine()) != null){
System.out.println(<strong class="highlight">line</strong>);
}
} catch (Exception e){
e.printStackTrace();
}
With that as a starting point, see if you can get the elements into your array and post back if you run into problems.
An idea is to load the entire file as a string and split the file by the linebreak character. Then just take the array[6] (the 6th index of the array) and you can access that line only.
Cute if your file has a zillion lines and you only need line number six.Quote:
Originally Posted by masternerdguy
kind regards,
Jos
What the other guy said. :) Besides, array[6] is the 7th index (A)Quote:
Originally Posted by masternerdguy