methods that return arrays

[Sally Curtis]

i am writing a method that returns an array full of students names. The students names are given in a file, so my method called ReadFile, reads the file and adds each line(name) to the array
i'm not sure my code is correct, plus i'm not familiar with writing methods that return and array.
If someone could comment on this code, i would really appreciate it.

 
 
public static DONT KNOW WHAT TO PUT HERE ReadFile(String FileName) throws IOException
{
 
String text="";
try
{
BufferedReader dataFile=new BufferedReader(new FileReader(FileName); 
Names=new String[8];
text= dataFile.readLine();
 
while(text!=null)
 
{
Names.add(ExtractString(text,1),ExtractString(text,2));
text=dataFile.readLine();
}
return Names;
}//try

catch(FileNotFoundException excpt)
{
System.err.println(excpt.getMessage());
return null;
}//catch
}//ReadFile

 
public static String ExtractString(String lineOfData, int itemNumber)
{
String dataItem="Token"+itemNumber+"not available";
int itemCount=0;
StringTokenizer dataList=new StringTokenizer(lineOfData);
int tokenCount=dataList.countTokens();
 
while((tokenCount>=itemNumber)&&(itemCount<itemNumber))
{
dataItem=dataList.nextToken();
itemCount++;
}
return dataItem;
}//ExtractString
 

 

[Craig Wood]

To return an array from a method is simple. You use the type with the array operator ([]). So to return an array of type int:

    public int[] getNumbers()
    {
        int a = 1;
        int b = 2;
        int c = 3;
        return new int[] { a, b, c};
    }

Make sure the type after the return keyword at the end of the method (or anywhere there is a return inside the method) is the same as the return type in the method declaration (at the top).

This example assumes there is only one name per line in the text file. There are a lot of ways to do these kind of things. Here we just read the names and add them to a string using a comma as sepatator and after the file reading is finished convert the string to an array.

import java.io.*;
 
public class ReturningAnArray
{
    public static void main(String[] args)
    {
        String fileName = "students.txt";
        String[] students = readFile(fileName);
        for(int i = 0; i < students.length; i++)
            System.out.println(students[i]);
    }
 
    public static String[] readFile(String fileName)
    {
        String names = "";
        BufferedReader br = null;
        try
        {
            br = new BufferedReader(new FileReader(fileName));
            String line;
            while((line = br.readLine()) != null)
                names += line + ",";         // collect the names
            br.close();
        }
        catch(FileNotFoundException fnfe)
        {
            System.out.println(fnfe.getMessage());
        }
        catch(IOException ioe)
        {
            System.out.println(ioe.getMessage());
        }
        // remove last "," (comma)
        names = names.substring(0, names.lastIndexOf(","));
        // make the string an array with new (1.4) String method
        String[] arrayOfNames = names.split(",");
        return arrayOfNames;
    }
}

[Sally Curtis]

im a bit confused, you said that you would commas as the separator, well what if in the text file, there are no commas separating the names for example
John Doe
Sue McGonnal
just spaces,
and also in the readFile method, what exactly does the .Split method do?

[Craig Wood]

In the example code above I am reading each line of the text file (and assuming one name per line) adding each name followed by a comma (as delimiter). You can see this in the while loop:

            while((line = br.readLine()) != null)
                names += line + ",";         // collect the names

After the while loop the String names holds all the names read from the file, separated by commas (that I added as I gathered the names). Then I remove the last (trailing) comma in preparation for converting the string to an array.

You can find the split method in the String api. It creates and returns an array of strings demarked by the delimeter specified in the argument ("," here).

I added some System.out.println statements to readFile to show what names looks like during the process. The output of names at the end is the same as the text file that contains the names (one name per line).

C:\jexp>java ReturningAnArray
names after while loop =
        John Carmody,Helen Shultz,Evelyn Jones,Harry Fuller,Sierra Mitchell,Gerr
y Smith,Horace Finley,Rebecca Illias,
names after removal of last comma =
        John Carmody,Helen Shultz,Evelyn Jones,Harry Fuller,Sierra Mitchell,Gerr
y Smith,Horace Finley,Rebecca Illias
John Carmody
Helen Shultz
Evelyn Jones
Harry Fuller
Sierra Mitchell
Gerry Smith
Horace Finley
Rebecca Illias

[Paul Santa Maria]

You might also want to consider using an ArrayList to read your items, then the toArray() as you return. That way, you can have your cake (ArrayList.add()) and eat it too.

For example:

  static String[] getStrings () {
    Collection strings = new ArrayList ();
 
    strings.add ("Tom");
    strings.add ("Jerry");
 
    return (String[])strings.toArray (new String[0]);
  }

[Sally Curtis]

my data file contains a list of the names but the list has no commas after each name. I tried making the delimeter ""+"" two spaces but it didnt work. so how would i accomplish making the delimeter equal to some kind of space?

also id like to thank the people in this post who helped. I really appreciate the help!

[Craig Wood]

You don't need commas in the file.
Is there more than one name per line in your file? If there are what does the file look like?
Here is the file I used in the example code above:

John Carmody
Helen Shultz
Evelyn Jones
Harry Fuller
Sierra Mitchell
Gerry Smith
Horace Finley
Rebecca Illias