Help with Java Arrays: Saving to output file

Question

public char[] calculateGrade(int [] scores, char [] grades){
    for (int r = 0; r < scores.length; r++){
        //System.out.println(scores[r] + " ");
        if (scores[r] > 90)
            grades[r] = 'A';
        else if (scores[r] > 80)
            grades[r] = 'B';
        else if (scores[r] > 70)
            grades[r] = 'C';
        else if (scores[r] > 60)
            grades[r] = 'D';
        else
            grades[r] = 'F';
    for (int i = 0; i < grades.length; i++)
        System.out.println(grades[i]);

    }
    return grades;

}

Above is a small part of my overall program that takes scores from a file and turns them into letter grades. I need to put these letter grades into that file. The letter grade needs to correspond with the score. There are 26 different scores one line at a time. I would put my entire code in here but it is really long. Please help guys!

The last for loop only prints all the grades multiple times. I am really confused... — Josh
– Josh, Commented Jul 12, 2011 at 23:53
By the way, I realize nobody else mentioned the problem with your code. Your loops are nested. So every time you read a score, you print all grades. Be careful with the brackets. — besamelsosu
– besamelsosu, Commented Aug 22, 2011 at 11:06

duffymo · Accepted Answer · 2011-07-12 23:56:31Z

3

I'd recommend having each method do one thing and do it well. Don't calculate grades and print them out.

public void printGrades(PrintStream ps, char [] grades) {
    for (char grade : grades) {
       ps.println(grade);
    }
}

public char[] calculateGrade(int [] scores){

    char [] grades = new char[scores.length];

    for (int r = 0; r < scores.length; r++){
        if (scores[r] > 90)
            grades[r] = 'A';
        else if (scores[r] > 80)
            grades[r] = 'B';
        else if (scores[r] > 70)
            grades[r] = 'C';
        else if (scores[r] > 60)
            grades[r] = 'D';
        else
            grades[r] = 'F';
    }
    return grades;

}

answered Jul 12, 2011 at 23:56

duffymo

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6 Comments

Mustafa Zengin Over a year ago

and I suppose, he only reads the scores from the file. So, "char [] grades" as a parameter of calculateGrade() is also a wrong approach.

Josh Over a year ago

I dont understand, you obviously are creating the grades array in the method and returning it to the class but how does the class understand it. Isnt it a local variable?

duffymo Over a year ago

I took the "char [] grades" out of the parameter list after realizing that the cut & paste solution was not preferred.

Josh Over a year ago

So instead of printing the grades, how would I assign them to a file? Lets say there are 20 lines of someones name and their score, I need to put the letter grade after that score. How would I go about doing this? Sorry for the noobness...

duffymo Over a year ago

You don't "assign" them to a file. You write to a file after opening it. Modify the method I gave you to include an array of names, scores and grades. Or, better yet, a List<Grade> or some other class that encapsulates name, score, and grade into a single unified thing. Java's an object-oriented language.

|

tskuzzy · Accepted Answer · 2011-07-12 23:57:09Z

1

Change your method to just the following:

public void calculateGrade(int[] scores, char[] grades){
    for (int r = 0; r < scores.length; r++) {
        if (scores[r] > 90)
            grades[r] = 'A';
        else if (scores[r] > 80)
            grades[r] = 'B';
        else if (scores[r] > 70)
            grades[r] = 'C';
        else if (scores[r] > 60)
            grades[r] = 'D';
        else
            grades[r] = 'F';
    }
}

There's no need to return grades since arrays are passed by reference anyways. Then in your calling method (main?), you should write grades to the file you want.

To write to a file, consult: http://www.exampledepot.com/egs/java.io/WriteToFile.html

So something like:

try {
    PrintWriter out = new PrintWriter(new BufferedWriter(new FileWriter("filename")));

    for( char grade : grades )
        out.println(grade);

    out.close();
} catch (IOException e) { }

answered Jul 12, 2011 at 23:57

tskuzzy

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2 Comments

Josh Over a year ago

Thanks man but the last part is a little too complicated lol. I am a junior CS student and I haven't learned about those keywords so far. So I need to keep it simple haha. But I understand the first part!

tskuzzy Over a year ago

That's just how you write to a file. Don't worry about the try or the catch. Just think of out.println as similar to System.out.println except writing to a file.

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