converting a string array to a double array

Question

I am trying to convert a list of numbers from a txt file into an array of numbers. There is 26 numbers, and each is on a different line in the text file. My code is

import java.io.*;
public class rocket {

    public static void main(String[] args) throws IOException, FileNotFoundException
    {
        BufferedReader b = new BufferedReader(new InputStreamReader(new FileInputStream("/Users/Jeremy/Documents/workspace/altitude.txt")));
        String[] stringArray = new String[25];
        double[] doubleArray = new double[stringArray.length];
        for(int i=0; i<25; i++)
        {
            stringArray[i] = b.readLine();
            doubleArray[i] = Double.parseDouble(stringArray[i]);
        }
        for(int i = 0; i<doubleArray.length; i++)
        {
            System.out.println(doubleArray[i]);
        }
    }
}

But every time I run it I get a number format exception. And if I try to just print out the strings I get an indexOutOfBounds exception

if there are 26 numbers you should be doing this new String[26]. This is causing the indexOutOfBoundsException — Breavyn
– Breavyn, Commented Mar 23, 2013 at 5:24
readLine() returns a string with the linebreak appended. Also, you don't need to create a string array. You can use 1 tempString variable inside the loop. Not sure how you'd handle the double[] size though, because I don't know Java. edit: For the doubles, use a vector. — user123
– user123, Commented Mar 23, 2013 at 5:24
I thought that the count started at the "zeroeth" term? And @Magtheridon96, I don't know how to do that, but I would appreciate it if you put that into an answer — user1940007
– user1940007, Commented Mar 23, 2013 at 5:41
@user1940007 They do however you are specifying the size here. You want 26 elements. Not 25. — Breavyn
– Breavyn, Commented Mar 23, 2013 at 5:44

stinepike · Accepted Answer · 2013-03-23 05:52:34Z

2

in question you have mentioned that there is 26 strings so declate

String[] stringArray = new String[26];

And The number format exception is occuring as readline returns with the linbreak. To read line you can do the following

 public String[] readLines(String filename) throws IOException {
        FileReader fileReader = new FileReader(filename);
        BufferedReader bufferedReader = new BufferedReader(fileReader);
        List<String> lines = new ArrayList<String>();
        String line = null;
        while ((line = bufferedReader.readLine()) != null) {
            lines.add(line);
        }
        bufferedReader.close();
        return lines.toArray(new String[lines.size()]);
    }

So by this logic you can get double by

public static Double[] readLines(String filename) throws IOException {
    FileReader fileReader = new FileReader(filename);
    BufferedReader bufferedReader = new BufferedReader(fileReader);
    List<Double> lines = new ArrayList<Double>();
    String line = null;
    while ((line = bufferedReader.readLine()) != null) {
        lines.add(Double.parseDouble(line));
    }
    bufferedReader.close();
    return lines.toArray(new Double[lines.size()]);
}

edited Mar 23, 2013 at 5:52

answered Mar 23, 2013 at 5:30

stinepike

54.9k14 gold badges95 silver badges115 bronze badges

Sign up to request clarification or add additional context in comments.

8 Comments

user1940007 Over a year ago

The rest of my method will be using derivatives, so I need the array to be a double, and this returns a string array.

stinepike Over a year ago

I just showed how you can parse the line .. from this string array you can modify the code to get double array

user1940007 Over a year ago

So I put this in the main, and directly copied and pasted the method that returns a double, and I still get the error message NumberFormatException System.out.println(Arrays.toString(readLines("/Users/Jeremy/Documents/workspace/altitude.txt")));

stinepike Over a year ago

:s.. just print the return values in system.out.print(readLines(filename)); if there is stil problem.. show the file

user1940007 Over a year ago

the file is just 60 2927 10170 21486 33835 45251 55634 65038 73461 80905 87368 92852 97355 100879 103422 104986 106193 110247 119626 136106 162096 199506 238776 277065 314375 350704 each number is on another line

|

Arun P Johny · Accepted Answer · 2013-03-23 05:36:12Z

1

Try

    BufferedReader b = new BufferedReader(
            new InputStreamReader(
                    new FileInputStream(
                            "D:/git-repo/general/misc_test/src/java/com/greytip/cougar/module/test/v2/controller/so/dump/data.txt")));

    List<String> lines = new ArrayList<String>();

    String line = null;
    while ((line = b.readLine()) != null) {
        lines.add(line);
    }

    String[] stringArray = lines.toArray(new String[lines.size()]);
    double[] doubleArray = new double[stringArray.length];
    for (int i = 0; i < stringArray.length; i++) {
        doubleArray[i] = Double.parseDouble(stringArray[i]);
    }

    for (int i = 0; i < doubleArray.length; i++) {
        System.out.println(doubleArray[i]);
    }

answered Mar 23, 2013 at 5:36

Arun P Johny

389k68 gold badges532 silver badges532 bronze badges

4 Comments

user1940007 Over a year ago

still has a NumberFormatException

Arun P Johny Over a year ago

can you share the text file

user1940007 Over a year ago

the file is just 60 2927 10170 21486 33835 45251 55634 65038 73461 80905 87368 92852 97355 100879 103422 104986 106193 110247 119626 136106 162096 199506 238776 277065 314375 350704 each number is on another line

user1940007 Over a year ago

Works, I realized that my file wasn't a pure txt file

m suresh · Accepted Answer · 2013-03-23 05:30:32Z

1

String[] stringArray = new String[26];

try this

answered Mar 23, 2013 at 5:30

m suresh

6591 gold badge8 silver badges26 bronze badges

Comments

TimonWang · Accepted Answer · 2013-03-23 05:30:00Z

    import java.io.*;
    public class Rocket {

        public static void main(String[] args) throws IOException, FileNotFoundException
        {
            BufferedReader b = new BufferedReader(new InputStreamReader(new FileInputStream("/Users/Jeremy/Documents/workspace/altitude.txt")));
            String[] stringArray = new String[25];
            double[] doubleArray = new double[stringArray.length];
            for(int i=0; i<25; i++)
            {
                stringArray[i] = b.readLine();
                try{
                    doubleArray[i] = Double.parseDouble(stringArray[i]);
                }catch(Exception e)
                {
                    e.printStackTrace();
                }
            }
            for(int i = 0; i<doubleArray.length; i++)
            {
                System.out.println(doubleArray[i]);
            }
        }
    }

Handle the Exception when parse a string to double please.

Collectives™ on Stack Overflow

converting a string array to a double array

4 Answers 4

8 Comments

4 Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

8 Comments

4 Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related