I am reading a file with comma separated values which when split into an array will have 10 values for each line . I expected the file to have line breaks so that
line = bReader.readLine()
will give me each line. But my file doesnt have a line break. Instead after the first set of values there are lots of spaces(465 to be precise) and then the next line begins.
So my above code of readLine() is reading the entire file in one go as there are no lined breaks. Please suggest how best to efficiently tackle this scenario.
One way is to replace String with 465 spaces in your text with new line character "\n" before iterating it for reading.
I second Ninan's answer: replace the 465 spaces with a newline, then run the function you were planning on running earlier.
For aesthetics and readability I would suggest using Regex's Pattern to replace the spaces instead of a long unreadable String.replace(" ").
Your code could like below, but replace 6 with 465:
// arguments are passed using the text field below this editor
public static void main(String[] args)
{
String content = "DOG,CAT MOUSE,CHEESE";
Pattern p = Pattern.compile("[ ]{6}",
Pattern.DOTALL | Pattern.CASE_INSENSITIVE);
String newString = p.matcher(content).replaceAll("\n");
System.out.println(newString);
}
My suggestion is read file f1.txt and write to anther file f2.txt by removing all empty lines and spaces then read f2.txt something like
FileReader fr = new FileReader("f1.txt");
BufferedReader br = new BufferedReader(fr);
FileWriter fw = new FileWriter("f2.txt");
String line;
while((line = br.readLine()) != null)
{
line = line.trim(); // remove leading and trailing whitespace
if (!line.equals("")) // don't write out blank lines
{
fw.write(line, 0, line.length());
}
}
Then try using your code.
You might create your own subclass of a FilterInputStream or a PushbackInputStream and pass that to an InputStreamReader. One overrides int read().
Such a class unfortunately needs a bit of typing. (A nice excercise so to say.)
private static final int NO_CHAR = -2;
private boolean fromCache;
private int cachedSpaces;
private int cachedNonSpaceChar = NO_CHAR;
int read() throws IOException {
if (fromCache) {
if (cachecSpaces > 0) ...
if (cachedNonSpaceChar != NO_CHAR) ...
...
}
int ch = super.read();
if (ch != -1) {
...
}
return ch;
}
The idea is to cache spaces till either a nonspace char, and in read() either take from the cache, return \n instead, call super.read() when not from cache, recursive read when space.
My understanding is that you have a flat CSV file without proper line break, which supposed to have 10 values on each line.
Updated:
1. (Recommended) You can use Scanner class with useDelimiter to parse csv effectively, assuming you are trying to store 10 values from a line:
public static void parseCsvWithScanner() throws IOException {
Scanner scanner = new Scanner(new File("test.csv"));
// set your delimiter for scanner, "," for csv
scanner.useDelimiter(",");
// storing 10 values as a "line"
int LINE_LIMIT = 10;
// implement your own data structure to store each value of CSV
int[] tempLineArray = new int[LINE_LIMIT];
int lineBreakCount = 0;
while(scanner.hasNext()) {
// trim start and end spaces if there is any
String temp = scanner.next().trim();
tempLineArray[lineBreakCount++] = Integer.parseInt(temp);
if (lineBreakCount == LINE_LIMIT) {
// replace your own logic for handling the full array
for(int i=0; i<tempLineArray.length; i++) {
System.out.print(tempLineArray[i]);
} // end replace
// resetting array and counter
tempLineArray = new int[LINE_LIMIT];
lineBreakCount = 0;
}
}
scanner.close();
}
Or use the BufferedReader.
You might not need the ArrayList to store all values if there is memory issue by replacing your own logic.
public static void parseCsv() throws IOException {
BufferedReader br = new BufferedReader(new FileReader(file));
// your delimiter
char TOKEN = ',';
// your requirement of storing 10 values for each "line"
int LINE_LIMIT = 10;
// tmp for storing from BufferedReader.read()
int tmp;
// a counter for line break
int lineBreakCount = 0;
// array for storing 10 values, assuming the values of CSV are integers
int[] tempArray = new int[LINE_LIMIT];
// storing tempArray of each line to ArrayList
ArrayList<int[]> lineList = new ArrayList<>();
StringBuilder sb = new StringBuilder();
while((tmp = br.read()) != -1) {
if ((char)tmp == TOKEN) {
if (lineBreakCount == LINE_LIMIT) {
// your logic to handle the current "line" here.
lineList.add(tempArray);
// new "line"
tempArray = new int[LINE_LIMIT];
lineBreakCount = 0;
}
// storing current value from buffer with trim of spaces
tempArray[lineBreakCount] =
Integer.parseInt(sb.toString().trim());
lineBreakCount++;
// clear the buffer
sb.delete(0, sb.length());
}
else {
// add current char from BufferedReader if not delimiter
sb.append((char)tmp);
}
}
br.close();
}
In Java, is there any method to read a particular line from a file? For example, read line 32 or any other line number.
For small files:
String line32 = Files.readAllLines(Paths.get("file.txt")).get(32)
For large files:
try (Stream<String> lines = Files.lines(Paths.get("file.txt"))) {
line32 = lines.skip(31).findFirst().get();
}
Unless you have previous knowledge about the lines in the file, there's no way to directly access the 32nd line without reading the 31 previous lines.
That's true for all languages and all modern file systems.
So effectively you'll simply read lines until you've found the 32nd one.
Not that I know of, but what you could do is loop through the first 31 lines doing nothing using the readline() function of BufferedReader
FileInputStream fs= new FileInputStream("someFile.txt");
BufferedReader br = new BufferedReader(new InputStreamReader(fs));
for(int i = 0; i < 31; ++i)
br.readLine();
String lineIWant = br.readLine();
Joachim is right on, of course, and an alternate implementation to Chris' (for small files only because it loads the entire file) might be to use commons-io from Apache (though arguably you might not want to introduce a new dependency just for this, if you find it useful for other stuff too though, it could make sense).
For example:
String line32 = (String) FileUtils.readLines(file).get(31);
http://commons.apache.org/io/api-release/org/apache/commons/io/FileUtils.html#readLines(java.io.File, java.lang.String)
You may try indexed-file-reader (Apache License 2.0). The class IndexedFileReader has a method called readLines(int from, int to) which returns a SortedMap whose key is the line number and the value is the line that was read.
Example:
File file = new File("src/test/resources/file.txt");
reader = new IndexedFileReader(file);
lines = reader.readLines(6, 10);
assertNotNull("Null result.", lines);
assertEquals("Incorrect length.", 5, lines.size());
assertTrue("Incorrect value.", lines.get(6).startsWith("[6]"));
assertTrue("Incorrect value.", lines.get(7).startsWith("[7]"));
assertTrue("Incorrect value.", lines.get(8).startsWith("[8]"));
assertTrue("Incorrect value.", lines.get(9).startsWith("[9]"));
assertTrue("Incorrect value.", lines.get(10).startsWith("[10]"));
The above example reads a text file composed of 50 lines in the following format:
[1] The quick brown fox jumped over the lazy dog ODD
[2] The quick brown fox jumped over the lazy dog EVEN
Disclamer: I wrote this library
Although as said in other answers, it is not possible to get to the exact line without knowing the offset (pointer) before. So, I've achieved this by creating an temporary index file which would store the offset values of every line. If the file is small enough, you could just store the indexes (offset) in memory without needing a separate file for it.
The offsets can be calculated by using the RandomAccessFile
RandomAccessFile raf = new RandomAccessFile("myFile.txt","r");
//above 'r' means open in read only mode
ArrayList<Integer> arrayList = new ArrayList<Integer>();
String cur_line = "";
while((cur_line=raf.readLine())!=null)
{
arrayList.add(raf.getFilePointer());
}
//Print the 32 line
//Seeks the file to the particular location from where our '32' line starts
raf.seek(raf.seek(arrayList.get(31));
System.out.println(raf.readLine());
raf.close();
Also visit the Java docs on RandomAccessFile for more information:
Complexity: This is O(n) as it reads the entire file once. Please be aware for the memory requirements. If it's too big to be in memory, then make a temporary file that stores the offsets instead of ArrayList as shown above.
Note: If all you want in '32' line, you just have to call the readLine() also available through other classes '32' times. The above approach is useful if you want to get the a specific line (based on line number of course) multiple times.
Another way.
try (BufferedReader reader = Files.newBufferedReader(
Paths.get("file.txt"), StandardCharsets.UTF_8)) {
List<String> line = reader.lines()
.skip(31)
.limit(1)
.collect(Collectors.toList());
line.stream().forEach(System.out::println);
}
No, unless in that file format the line lengths are pre-determined (e.g. all lines with a fixed length), you'll have to iterate line by line to count them.
In Java 8,
For small files:
String line = Files.readAllLines(Paths.get("file.txt")).get(n);
For large files:
String line;
try (Stream<String> lines = Files.lines(Paths.get("file.txt"))) {
line = lines.skip(n).findFirst().get();
}
In Java 7
String line;
try (BufferedReader br = new BufferedReader(new FileReader("file.txt"))) {
for (int i = 0; i < n; i++)
br.readLine();
line = br.readLine();
}
Source: Reading nth line from file
If you are talking about a text file, then there is really no way to do this without reading all the lines that precede it - After all, lines are determined by the presence of a newline, so it has to be read.
Use a stream that supports readline, and just read the first X-1 lines and dump the results, then process the next one.
It works for me:
I have combined the answer of
Reading a simple text file
But instead of return a String I am returning a LinkedList of Strings. Then I can select the line that I want.
public static LinkedList<String> readFromAssets(Context context, String filename) throws IOException {
BufferedReader reader = new BufferedReader(new InputStreamReader(context.getAssets().open(filename)));
LinkedList<String>linkedList = new LinkedList<>();
// do reading, usually loop until end of file reading
StringBuilder sb = new StringBuilder();
String mLine = reader.readLine();
while (mLine != null) {
linkedList.add(mLine);
sb.append(mLine); // process line
mLine = reader.readLine();
}
reader.close();
return linkedList;
}
Use this code:
import java.nio.file.Files;
import java.nio.file.Paths;
public class FileWork
{
public static void main(String[] args) throws IOException {
String line = Files.readAllLines(Paths.get("D:/abc.txt")).get(1);
System.out.println(line);
}
}
You can use LineNumberReader instead of BufferedReader. Go through the api. You can find setLineNumber and getLineNumber methods.
You can also take a look at LineNumberReader, subclass of BufferedReader. Along with the readline method, it also has setter/getter methods to access line number. Very useful to keep track of the number of lines read, while reading data from file.
public String readLine(int line){
FileReader tempFileReader = null;
BufferedReader tempBufferedReader = null;
try { tempFileReader = new FileReader(textFile);
tempBufferedReader = new BufferedReader(tempFileReader);
} catch (Exception e) { }
String returnStr = "ERROR";
for(int i = 0; i < line - 1; i++){
try { tempBufferedReader.readLine(); } catch (Exception e) { }
}
try { returnStr = tempBufferedReader.readLine(); } catch (Exception e) { }
return returnStr;
}
you can use the skip() function to skip the lines from begining.
public static void readFile(String filePath, long lineNum) {
List<String> list = new ArrayList<>();
long totalLines, startLine = 0;
try (Stream<String> lines = Files.lines(Paths.get(filePath))) {
totalLines = Files.lines(Paths.get(filePath)).count();
startLine = totalLines - lineNum;
// Stream<String> line32 = lines.skip(((startLine)+1));
list = lines.skip(startLine).collect(Collectors.toList());
// lines.forEach(list::add);
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
list.forEach(System.out::println);
}
EASY WAY - Reading a line using line number.
Let's say Line number starts from 1 till null .
public class TextFileAssignmentOct {
private void readData(int rowNum, BufferedReader br) throws IOException {
int n=1; //Line number starts from 1
String row;
while((row=br.readLine()) != null) { // Reads every line
if (n == rowNum) { // When Line number matches with which you want to read
System.out.println(row);
}
n++; //This increments Line number
}
}
public static void main(String[] args) throws IOException {
File f = new File("../JavaPractice/FileRead.txt");
FileReader fr = new FileReader(f);
BufferedReader br = new BufferedReader(fr);
TextFileAssignmentOct txf = new TextFileAssignmentOct();
txf.readData(4, br); //Read a Specific Line using Line number and Passing buffered reader
}
}
for a text file you can use an integer with a loop to help you get the number of the line, don't forget to import the classes we are using in this example
File myObj = new File("C:\\Users\\LENOVO\\Desktop\\test.txt");//path of the file
FileReader fr = new FileReader(myObj);
fr.read();
BufferedReader bf = new BufferedReader(fr); //BufferedReader of the FileReader fr
String line = bf.readLine();
int lineNumber = 0;
while (line != null) {
lineNumber = lineNumber + 1;
if(lineNumber == 7)
{
//show line
System.out.println("line: " + lineNumber + " has :" + line);
break;
}
//lecture de la prochaine ligne, reading next
line = bf.readLine();
}
They are all wrong I just wrote this in about 10 seconds.
With this I managed to just call the object.getQuestion("linenumber") in the main method to return whatever line I want.
public class Questions {
File file = new File("Question2Files/triviagame1.txt");
public Questions() {
}
public String getQuestion(int numLine) throws IOException {
BufferedReader br = new BufferedReader(new FileReader(file));
String line = "";
for(int i = 0; i < numLine; i++) {
line = br.readLine();
}
return line; }}
Importing a large list of words and I need to create code that will recognize each word in the file. I am using a delimiter to recognize the separation from each word but I am receiving a suppressed error stating that the value of linenumber and delimiter are not used. What do I need to do to get the program to read this file and to separate each word within that file?
public class ASCIIPrime {
public final static String LOC = "C:\\english1.txt";
#SuppressWarnings("null")
public static void main(String[] args) throws IOException {
//import list of words
#SuppressWarnings("resource")
BufferedReader File = new BufferedReader(new FileReader(LOC));
//Create a temporary ArrayList to store data
ArrayList<String> temp = new ArrayList<String>();
//Find number of lines in txt file
String line;
while ((line = File.readLine()) != null)
{
temp.add(line);
}
//Identify each word in file
int lineNumber = 0;
lineNumber++;
String delimiter = "\t";
//assess each character in the word to determine the ascii value
int total = 0;
for (int i=0; i < ((String) line).length(); i++)
{
char c = ((String) line).charAt(i);
total += c;
}
System.out.println ("The total value of " + line + " is " + total);
}
}
This smells like homework, but alright.
Importing a large list of words and I need to create code that will recognize each word in the file. What do I need to do to get the program to read this file and to separate each word within that file?
You need to...
Read the file
Separate the words from what you've read in
... I don't know what you want to do with them after that. I'll just dump them into a big list.
The contents of my main method would be...
BufferedReader File = new BufferedReader(new FileReader(LOC));//LOC is defined as class variable
//Create an ArrayList to store the words
List<String> words = new ArrayList<String>();
String line;
String delimiter = "\t";
while ((line = File.readLine()) != null)//read the file
{
String[] wordsInLine = line.split(delimiter);//separate the words
//delimiter could be a regex here, gotta watch out for that
for(int i=0, isize = wordsInLine.length(); i < isize; i++){
words.add(wordsInLine[i]);//put them in a list
}
}
You can use the split method of the String class
String[] split(String regex)
This will return an array of strings that you can handle directly of transform in to any other collection you might need.
I suggest also to remove the suppresswarning unless you are sure what you are doing. In most cases is better to remove the cause of the warning than supress the warning.
I used this great tutorial from thenewboston when I started off reading files: https://www.youtube.com/watch?v=3RNYUKxAgmw
This video seems perfect for you. It covers how to save file words of data. And just add the string data to the ArrayList. Here's what your code should look like:
import java.io.*;
import java.util.*;
public class ReadFile {
static Scanner x;
static ArrayList<String> temp = new ArrayList<String>();
public static void main(String args[]){
openFile();
readFile();
closeFile();
}
public static void openFile(){
try(
x = new Scanner(new File("yourtextfile.txt");
}catch(Exception e){
System.out.println(e);
}
}
public static void readFile(){
while(x.hasNext()){
temp.add(x.next());
}
}
public void closeFile(){
x.close();
}
}
One thing that is nice with using the java util scanner is that is automatically skips the spaces between words making it easy to use and identify words.
So I can search for a string in my text file, however, I wanted to sort data within this ArrayList and implement an algorithm. Is it possible to read from a text file and the values [Strings] within the text file be stored in a String[] Array.
Also is it possible to separate the Strings? So instead of my Array having:
[Alice was beginning to get very tired of sitting by her sister on the, bank, and of having nothing to do:]
is it possible to an array as:
["Alice", "was" "beginning" "to" "get"...]
.
public static void main(String[]args) throws IOException
{
Scanner scan = new Scanner(System.in);
String stringSearch = scan.nextLine();
BufferedReader reader = new BufferedReader(new FileReader("File1.txt"));
List<String> words = new ArrayList<String>();
String line;
while ((line = reader.readLine()) != null) {
words.add(line);
}
for(String sLine : words)
{
if (sLine.contains(stringSearch))
{
int index = words.indexOf(sLine);
System.out.println("Got a match at line " + index);
}
}
//Collections.sort(words);
//for (String str: words)
// System.out.println(str);
int size = words.size();
System.out.println("There are " + size + " Lines of text in this text file.");
reader.close();
System.out.println(words);
}
To split a line into an array of words, use this:
String words = sentence.split("[^\\w']+");
The regex [^\w'] means "not a word char or an apostrophe"
This will capture words with embedded apostrophes like "can't" and skip over all punctuation.
Edit:
A comment has raised the edge case of parsing a quoted word such as 'this' as this.
Here's the solution for that - you have to first remove wrapping quotes:
String[] words = input.replaceAll("(^|\\s)'([\\w']+)'(\\s|$)", "$1$2$3").split("[^\\w']+");
Here's some test code with edge and corner cases:
public static void main(String[] args) throws Exception {
String input = "'I', ie \"me\", can't extract 'can't' or 'can't'";
String[] words = input.replaceAll("(^|[^\\w'])'([\\w']+)'([^\\w']|$)", "$1$2$3").split("[^\\w']+");
System.out.println(Arrays.toString(words));
}
Output:
[I, ie, me, can't, extract, can't, or, can't]
Also is it possible to separate the Strings?
Yes, You can split string by using this for white spaces.
String[] strSplit;
String str = "This is test for split";
strSplit = str.split("[\\s,;!?\"]+");
See String API
Moreover you can also read a text file word by word.
Scanner scan = null;
try {
scan = new Scanner(new BufferedReader(new FileReader("Your File Path")));
} catch (FileNotFoundException e) {
e.printStackTrace();
}
while(scan.hasNext()){
System.out.println( scan.next() );
}
See Scanner API
I am trying to read from a file to an array. I tried two different styles and both aren't working. Below are the two styles.
Style 1
public class FileRead {
int i;
String a[] = new String[2];
public void read() throws FileNotFoundException {
//Z means: "The end of the input but for the final terminator, if any"
a[i] = new Scanner(new File("C:\\Users\\nnanna\\Documents\\login.txt")).useDelimiter("\\n").next();
for(i=0; i<=a.length; i++){
System.out.println("" + a[i]);
}
}
public static void main(String args[]) throws FileNotFoundException{
new FileRead().read();
}
}
Style 2
public class FileReadExample {
private int j = 0;
String path = null;
public void fileRead(File file){
StringBuilder attachPhoneNumber = new StringBuilder();
try{
FileReader read = new FileReader(file);
BufferedReader bufferedReader = new BufferedReader(read);
while((path = bufferedReader.readLine()) != null){
String a[] = new String[3];
a[j] = path;
j++;
System.out.println(path);
System.out.println(a[j]);
}
bufferedReader.close();
}catch(IOException exception){
exception.printStackTrace();
}
}
I need it to read each line of string and store each line in an array. But neither works. How do I go about it?
Do yourself a favor and use a library that provides this functionality for you, e.g.
Guava:
// one String per File
String data = Files.toString(file, Charsets.UTF_8);
// or one String per Line
List<String> data = Files.readLines(file, Charsets.UTF_8);
Commons / IO:
// one String per File
String data = FileUtils.readFileToString(file, "UTF-8");
// or one String per Line
List<String> data = FileUtils.readLines(file, "UTF-8");
It's not really clear exactly what you're trying to do (partly with quite a lot of code commented out, leaving other code which won't even compile), but I'd recommend you look at using Guava:
List<String> lines = Files.readLines(file, Charsets.UTF_8);
That way you don't need to mess around with the file handling yourself at all.