Closed. This question needs debugging details. It is not currently accepting answers.
Edit the question to include desired behavior, a specific problem or error, and the shortest code necessary to reproduce the problem. This will help others answer the question.
Closed 7 years ago.
Improve this question
I am making a program to take data from a .txt document, I have used the BufferedReader method which goes through the document. It then prints the the documents contents into the console. I cannot however for the life of me figure out how to get the contents from the BufferedReader into a string array so I can then further manipulate it. Any help?
The method Files.readAllLines reads a file into a List<String>, one String per line in the original file. The method Files.readAllBytes just reads a file into a byte array if that's your style. These are both part of the Java NIO 2 library, part of Java SE 7.
Path myFile = Paths.get("hello_world.txt");
List<String> fileLines = Files.readAllLines(myFile);
use DataInputStream instead of BufferedReader
DataInputStream is = new DataInputStream (new FileInputStream ("myFileName"));
then you can store a String with methtod call is.readUTF ();
If you want a String[] array containing the lines of the document, you could use BufferedReader.readLine(), and stuff the lines into a List<String> instead of printing them.
Here's how you can create a list of Strings:
List<String> lines = new ArrayList<String>();
And here's how you can add to it:
String line = null;
while( (line = reader.readLine()) != null ) {
lines.add( line );
}
Related
Closed. This question needs details or clarity. It is not currently accepting answers.
Want to improve this question? Add details and clarify the problem by editing this post.
Closed 4 months ago.
Improve this question
I need to read from a text file in java and pass that information through a polymorphic method. My idea is a CryptoWallet in a .txt file reading as coin, amount and value, where in the text file its represented as Bitcoin 100 1.25.
Ive got the code reading from the file and printing it, as below.
public class CryptoCurrencies
public static void main (String[] args) throws IOException
{
System.out.println("Welcome to your Crypto Wallet"
+ "\nCurrently, you only own one coin.");
File CryptoWallet = new File("/Users/curti/OneDrive/Desktop/crypto.txt");
Scanner scan = new Scanner(CryptoWallet);
String fileContent = " ";
while(scan.hasNextLine())
{
System.out.println(scan.nextLine());
continue;
}
My main issue is actually getting the text file too recognise the numbers as doubles and variables, and assigning them to run through a polymorphic method. I understand the polymorphism side, but if anyone has any ideas for a possible polymorphic method id really appreciate it, having trouble thinking at the moment!
Thanks everyone.
It is unclear what role polymorphism is supposed to have here.
Assuming that each row represents a record and each record has the same form then we can parse each row in an identical fashion. That allows you to extract the numeric values using the parse methods in the appropriate Number classes.
For instance...
while(scan.hasNextLine()) {
String line = scan.nextLine());
String[] tokens = line.split(" ");
String name = tokens[0];
int amount = Integer.parse(tokens[1]);
double value = Double.parse(tokens[2]);
}
p.s. obligatory comment that you shouldn't represent money in floating point variables.
Split the current line by space or "\s+" regex, check if the length is 3, then use the double.parse function from the double object on the 2nd and 3rd element in the array.
Closed. This question needs debugging details. It is not currently accepting answers.
Edit the question to include desired behavior, a specific problem or error, and the shortest code necessary to reproduce the problem. This will help others answer the question.
Closed 9 months ago.
Improve this question
I want to essentially read the contents of csv file and want to input into one string to return. I tried this and it doesnt quite work:
File file = new File(aaa.csv);
FileWriter fw = new FileWriter(file);
BufferReader bw = new BufferReader(fw);
String s;
while (bw.readLine() != null) {
s += (bw.readLine());
}
fw.close();
Is there a easier solution to reading csv file into string that works?
To read the entire file, assuming Java 11 and above, you can simply do:
String content = Files.readString(Paths.get("aaa.csv"));
note that if the file is very large memory becomes a problem.
Closed. This question needs details or clarity. It is not currently accepting answers.
Want to improve this question? Add details and clarify the problem by editing this post.
Closed 5 years ago.
Improve this question
I am reading a text file in Java that looks like this,
"
Q1. You are given a train data set having 1000 columns and 1 million rows. The data set is based on a classification problem. Your manager has asked you to reduce the dimension of this data so that model computation time can be reduced. Your machine has memory constraints. What would you do? (You are free to make practical assumptions.)
Q2. Is rotation necessary in PCA? If yes, Why? What will happen if you don’t rotate the components?
Q3. You are given a data set. The data set has missing values which spread along 1 standard deviation from the median. What percentage of data would remain unaffected? Why? "
Now, I want to read this file and then store each of these sentences(questions) in a string array. How can I do that in java?
I tried this,
String mlq = new String(Files.readAllBytes(Paths.get("MLques.txt")));
String[] mlq1=mlq.split("\n\n");
But this is not working.
Try this
String mlq = new String(Files.readAllBytes(Paths.get("MLQ.txt")));
String[] mlq1=mlq.split("\r\n\r\n");
System.out.println(mlq1.length);
System.out.println(Arrays.toString(mlq1));
This should do it by line gap of 2 lines.
File file = new File("C:\\MLques.txt");
BufferedReader br = new BufferedReader(new FileReader(file));
String st;
while ((st = br.readLine()) != null) {
System.out.println(st + "\n");
}
I think it will work.
This is a piece of code from one of my project.
public static List<String> readStreamByLines(InputStream in) throws IOException {
return IOUtils.readLines(in, StandardCharsets.UTF_8).stream()
.map(String::trim)
.collect(Collectors.toList());
}
But!!! If you have really big file, then collecting all content into a List is not good. You have to read InputStream line by line and do all you need for every single row.
Closed. This question does not meet Stack Overflow guidelines. It is not currently accepting answers.
This question does not appear to be about programming within the scope defined in the help center.
Closed 7 years ago.
Improve this question
I am trying to write a method for swapping columns of a text file using java.
can someone show or tell me how to write a method to swap two columns of a file in java ? both columns are seperated by a space
One possible method:
Read in file and split data (see here reading tab delimited textfile java)
Overwrite file with same data read in, but column order switched.
Read every line of the file
ArrayList<String[]> aryL = new ArrayList<String[]>();
for each line of file
aryl.add(eachline.split(","));
for(String[] sArr: arrL)
//Swap the elements and print or write to file
you could read each line of a file and try
String buffer = "";
//for each line of input
String[] columns = line.split(" ");
buffer+= columns[1] + " " + columns[0] + "\n";
//end for
then overwrite the file with your buffer String
Closed. This question needs details or clarity. It is not currently accepting answers.
Want to improve this question? Add details and clarify the problem by editing this post.
Closed 8 years ago.
Improve this question
I am making a some large project. In that I am stuck at one place. I am using the following code to read from the file:
String str = null;
FileReader fr = new FileReader("H:\\Eclipse\\Emulator\\progin8085.txt");
BufferedReader br = new BufferedReader(fr);
str = br.readLine(); //using it in a loop from 0 to total_no_of_lines
Now I when I reached suppose at line 8(counting lines numbers while entering data to the file), I want to go back to line 3 or 4 or any and again want to read and execute each statement. How to read previous statements using BufferedReader only? If it is not possible, any other solution?
Some Readers support marks. You can use those to rewind the file. A particularly useful Reader (imo) is the LineNumberReader and it supports marks. This sort of code might suit your needs.
public static int final READ_AHEAD_LIMIT = 100000;
LineNumberReader lnReader = new LineNumberReader(reader);
while (youWantToRead) {
...
if (mightBeInterestingLater) {
lnReader.mark(READ_AHEAD_LIMIT);
}
...
if (nowWantToRewind) {
lnReader.reset();
// We're now at whatever place mark() was last called at.
}
Save all the lines of text file in String[] StrArray and do whatever you want.