Java Extracting values from text files

Question

I have many text files (up to 20) and each file has it's contents like this

21.0|11|1/1/1997
13.3|12|2/1/1997
14.6|9|3/1/1997

and every file has approximately more than 300 lines.

so the problem I'm facing is this, how can I extract all and only the first values of the file's content.

for example I want to extract the values (21.0,13.3,14.6.....etc) so I can decide the max number and minimum in all of the 20 files.

I have wrote this code from my understanding to experience it on of the files but it didn't work

  String inputFileName = "Date.txt";
 File inputFile = new File(inputFileName);
 Scanner input = new Scanner(inputFile);
 int count = 0;
 while (input.hasNext()){
     double line = input.nextDouble(); //Error occurs "Exception in thread "main" java.util.InputMismatchException" 
     count++;
     double [] lineArray= new double [365];
     lineArray[count]= line;
     System.out.println(count);
      for (double s : lineArray){
       System.out.println(s);
          System.out.println(count);

and this one too

 String inputFileName = "Date.txt";
 File inputFile = new File(inputFileName);
 Scanner input = new Scanner(inputFile);

 while (input.hasNext()){
     String line = input.nextLine();
     String [] lineArray = line.split("//|");
      for (String s : lineArray){
       System.out.println(s+" ");
 }

• Note: I'm still kind of a beginner in Java

I hope I was clear and thanks

Solution 1

For each line of text, check whether it contains the pipe character. If it does, grab the first portion of the text and parse it to double.

double val = 0.0;
Scanner fScn = new Scanner(new File(“date.txt”));
while(fScn.hasNextLine()){   //Can also use a BufferedReader
    data = fScn.nextLine();
    if(data.contains("|"))    //Ensure line contains "|"
        val = Double.parseDouble(data.substring(0, data.indexOf("|")));  //grab value
}

Solution 2

Or you could try some streams, cool stuff

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;

public class MinMaxPrinter {

    public static void main(String[] args) {
        final List<String> files = Arrays.asList("file", "names", "that", "you", "need");

        new MinMaxPrinter().printMinMax(files);
    }

    public void printMinMax(List<String> fileNames) {
        List<Double> numbers = fileNames.stream()
                .map(Paths::get)
                .flatMap(this::toLines)
                .map(line -> line.split("\\|")[0])
                .map(Double::parseDouble)
                .collect(Collectors.toList());

        double max = numbers.stream().max(Double::compare).get();
        double min = numbers.stream().min(Double::compare).get();

        System.out.println("Min: " + min + " Max: " + max);
    }

    private Stream<String> toLines(Path path) {
        try {
            return Files.lines(path);
        } catch (IOException e) {
            return Stream.empty();
        }
    }
}

Comments

[isaias-b]

This question deals about doing your work. This site is supposed to be used to manage specific programming problems. Provide your attempts and if you have a certain problem post a specific question.

[user3437460]

@John Do you know how to read a line of text from the textfile?

[John]

Yes I do know how to read from the textfile

[John]

you can see my work in the question it was what I tried so far but no luck

[Tom]

" but it didn't work " Any chance to get more information about your problem, than this? :)

[RealSkeptic]

Your second attempt is nearly right. You have to note the difference between a slash / and a backslash \​.

[John]

@Tom well in first code I got the Error Exception in thread "main" java.util.InputMismatchException

[John]

@RealSkeptic yes right it was a mistake there and I noticed it thanks but still it doesn't solve my problem yet , how do I extract the value now ?

[Tom]

Well, do you like to post that info in your question? How should we know, that you have this problem if you don't tell us about it? Btw: please don't forget the exception stacktrace. And please mark the line where the exception occurs.

[Phani]

Can you please explain the code required on how it would resolve the issue?

[John]

Thanks I really needed to know how to grab the value thanks again

[John]

Thanks I really appreciate your effort