CODEWITHSUNDEEP
javaarraysfilejava.util.scanner
Ajmal
Ajmal

Reputation: 544

How to get the number of lines from a text file in java?

I'm a novice in Java. I want to find the number of line in a test file so that I can use it for array size. What my initial thought was to create a loop and update an int variable. like this:

Scanner file  = new Scanner(new File("data.text"));
int n = 0;
while(file.hasNextLine()) {
    file.nextLine();
    n++;
 }
int[] array = new int[n];

this doesn't work for me because the scanner file is at the end of the text file. I won't be able to read the text file unless I close the original one and create a new scanner object. Is there a better way to execute this?

Upvotes: 1

Views: 16532

Answers (4)

Tahir Hussain Mir
Tahir Hussain Mir

Reputation: 2626

Okay. Here is the simple answer to your question. You want to use the same Scanner object to read the file again from beginning without closing it.
It is impossible to do so..


Reason: The various kinds of input types it supports.These don't store the results after they have been passed on, so they don't support resetting.
So the elegant solution is to create a new Scanner Object.

Upvotes: 0

GuiSim
GuiSim

Reputation: 7559

Depending on what exactly you need to do, you might want to keep the whole file in memory.

List<String> lines = Files.readAllLines(Paths.get("data.text"));
// Here you can easily obtain the list size
lines.size()

If you don't need the actual lines or not all of them, you can do something like this

long lineCount = Files.lines(Paths.get("data.text")).count();

Since it's a Java 8 Stream, you can filter, parse or do whatever you want with the lines.

Upvotes: 2

ItamarG3
ItamarG3

Reputation: 4122

You can use BufferedReader and FileReader:

FileReader in = new FileReader("data.txt");
BufferedReader br = new BufferedReader(in);// use this only if you have large files, meaning that each line is very long.
int n = 0;
while (br.readLine() != null) {
    n++;

}
System.out.println(n);
in.close();
int[] array = new int[n];

Also, you can use an ArrayList instead of an array, but that would depend on how you want to use the line count.

If your file isn't very big, you can simply do this:

FileReader in = new FileReader("data.txt");
int n = 0;
while ((in.readLine() != null)) {
    n++;

}
System.out.println(n);
in.close();
int[] array = new int[n];

Upvotes: 0

Naghaveer R
Naghaveer R

Reputation: 2944

If you are using 1.7+, You can directly store to array like this.

import java.io.File;

import java.nio.charset.Charset;
import java.nio.file.Files;
import java.nio.file.Path;

import java.util.List;

// more code

Path filePath = new File("fileName").toPath();
Charset charset = Charset.defaultCharset();        
List<String> stringList = Files.readAllLines(filePath, charset);
String[] stringArray = stringList.toArray(new String[]{});

Upvotes: 4

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