JAVA: read .txt file and store doubles into array

Question

I have the following code already, which goes as far as appending the doubles.

Scanner sc1 = new Scanner(System.in);

try {

    System.out.println("Enter filename:");
    String name = sc1.nextLine();//determines name of file
    File file = new File(name);//creates above file     
    FileReader fileReader = new FileReader(file);//file is read 
    BufferedReader bufferedReader = new BufferedReader(fileReader );//BufferReader reads file, line by line
    StringBuffer stringBuffer = new StringBuffer();//appended to StringBuffer
    String line;//reads each 

    while ((line = bufferedReader.readLine()) != null) 
    {
        stringBuffer.append(line + "\n");           
    }

    fileReader.close();
    System.out.println("Contents of file:");
    System.out.println(stringBuffer.toString());

    } 

catch (IOException e) 
{
    e.printStackTrace();
}

The code reads a file that has a double on each line

ex:

1

2

3

4

5

...

How do I store each of these doubles into an array?

hitz · Accepted Answer · 2015-05-12 17:05:31Z

2

If you want to stick to using Array only, convert StringBuffer to String[] like this:

    String [] stringArray = stringBuffer.split("\n");

Then convert string array to double array:

    Double [] doubleArray = new Double[stringArray.size];
    for(int i=0 : i < stringArray.size : i++){  
        doubleArray[i] = Doube.parseDouble(stringArray[i]);  
    }

If you must use StringBuffer, you can divide into array by StringTokenizer class.
Alternatively, you can use String instead of StringBuffer and then split() method will work with de-limiter.

edited May 12, 2015 at 17:05

answered May 12, 2015 at 16:03

hitz

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2 Comments

Ben Over a year ago

Thanks. I'd like to stick with Arrays, and I used your code. But it tells me that the method split("\n") is undefined. Also, I cannot directly convert the elements in the String array into the double array dataArray[i] = stringArray[i];

hitz Over a year ago

I have updated my answer. String Array should now convert to Double. For split() you have two options as highlighted in main post.

Ryan · Accepted Answer · 2015-05-12 15:54:56Z

2

You could use an ArrayList:

ArrayList<Double> doubles = new ArrayList<Double>();
while ((line = bufferedReader.readLine()) != null) 
{
    doubles.add(Double.parseDouble(line));        
}

answered May 12, 2015 at 15:54

Ryan

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3 Comments

Ben Over a year ago

I've never used ArrayList before. I notice that no array is declared above, so I was wondering how I implement the above code into a specific array?

Azerogg Over a year ago

save the final result into a String, use String.split() to split it into an array.Sorry about the answer, misunderstood what you were looking for.

Ryan Over a year ago

With the ArrayList, you don't need the StringBuffer at all. I instantiated the array in my code, you can copy that exactly. If you need help printing out the values of an ArrayList, just google "printing out values of ArrayList"

Laurentiu L. · Accepted Answer · 2015-05-12 15:58:31Z

1

Basic solution

    ArrayList<Double> doubles = new ArrayList<>();
    while ((line = bufferedReader.readLine()) != null)
    {
        stringBuffer.append(line + "\n");
        try{
            double value = Double.parseDouble(line );
            doubles.add(value);
        } catch(NullPointerException e){
            //null string
        } catch(NumberFormatException e){
            //no parsable on the current line
        }
    }

answered May 12, 2015 at 15:58

Laurentiu L.

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Comments

Azerogg · Accepted Answer · 2015-05-12 16:01:01Z

0

I don't get the problem...Just make an array that stores the contents of the line as the file is read.

answered May 12, 2015 at 16:01

Azerogg

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