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Thread: Help with Arrays

  1. #1
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    Default Help with Arrays

    Hey yall,

    This is my first Java Programming course and I'm a little stuck on the arrays section. Our assignment is to create multiple single and multidimensional arrays and also create multiple methods. The following is the assignment:

    1.A method that accepts an array of doubles and returns the highest double number in the array.(Highest Grade)
    2. A method that accepts an array of doubles and returns the lowest double number in the array.(Lowest Grade)
    3. A method that accepts an array of doubles and returns the average of the numbers in the array as a double.(Average Grade)
    4. A method that accepts a double number and returns a String letter grade.
    5. A method that has no input but returns a double array of student grades.
    6. A method that accepts an integer for input and returns the name equivalent for numbers 1 – 10 and adds the correct two letter extension to numbers after that. This should be used when asking for the student's name and grades like:
    "Please enter the first student's name: " and "Please enter the first grade: " ... second grade: ...
    7. Use a String Array to store the student names along with a parallel, double[][] multidimensional array to store all of the student grades

    The flow of the program should look like this:

    1.Ask for number of students
    a. Collect number of students
    2. Create student name array and multidimensional grades array
    3. Collect each student’s information
    a.Ask for first student’s name and assign it to students[]
    student[i] = input.next();
    b. Call the method that collects student grades and assign it to the grades array
    grades[i] = collectGrades();
    4. Do this for each student (loop back to 3)
    5. When all of the information is collected into the parallel arrays, for each student:
    a. System.out.print() a line that has the proper header
    b. For each student output the information collected in the proper format using the other required methods.

    The problem I'm having is getting it to loop back. I can collect the number of students, the name of that first student, the grades for that student and it will give the output - but I'm confused on how to get it to loop back to ask for the name and the grades again. I'm also confused on how to pass the data from grades to the multidimensional array. Attached is my code:

    Thanks so much for your help in advance!

    import java.util.*;
    public class Midterm {
     
    	public static void main(String[] args) {
    		Scanner input = new Scanner(System.in);
     
    		System.out.println("Enter the number of students: ");
    		int numofStudents = input.nextInt();
     
     
    		// define arrays
    		String[] studentName = new String[numofStudents];
    		double[][] scores = new double[numofStudents][];
     
     
    		// for loop for student's names
     
    		for (int n = 0;n < 1; n++){
    		System.out.println("Enter the " +  numName(n+1) + " student's name(s): ");
    		studentName[n] = input.next();
     
    		}// end for
     
    		//call collectGrades
    		double grades[] = collectGrades();
     
     
     
    		//output
    		System.out.println("Student Name\tHigh Score\tLow Score\tAverage\tGrade");
    	    System.out.println("----------------------------------------------------------");
    	    for(int s = 0;s < numofStudents;s++) {
    			System.out.println(studentName[0 + s] + "\t\t" +highGrade(grades) + "\t\t" +lowGrade(grades)  + "\t\t\t" +(averageGrade(grades)));
     
     
    	    }
    		}
     
     
     
    	public static double[] collectGrades() {
    		Scanner input = new Scanner(System.in);
    		System.out.println("How many grades will you be entering" + "\n for this student?");
    		int numGrades = input.nextInt();
     
    		double grades[] = new double[numGrades];
     
    		//collect grades
    		for(int g = 0;g < grades.length; g++) {
    			System.out.println("Please enter the " +numName(g+1) + " grade:");
    			grades[g] = input.nextDouble();
     
    		} // end for loop
     
    		return grades;
    	} // end collectGrades
     
    	public static double highGrade (double arrayIn[]) {
    		Arrays.sort(arrayIn);
    		return arrayIn[arrayIn.length -1];
     
    	} // end highGrade
     
    	public static double lowGrade (double arrayIn[]) {
    		Arrays.sort(arrayIn);
    		return arrayIn[0];
     
    	} // end highGrade
     
    	public static double averageGrade(double arrayIn[]) {
    		double avgGrade = 0.0;
    		for(int i = 0;i < arrayIn.length;i++) {
    			avgGrade += arrayIn[i];
     
    		} // end for
     
    		return avgGrade/arrayIn.length;
     
    	} // end averageGrade
     
     
    	public static String numName(int intIn) {
    		String numName = "";
    		switch(intIn) {
    		case 1:
    			numName = "first";
    			break;
    		case 2: 
    			numName = "second";
    			break;
    		case 3:
    			numName = "third";
    			break;
    		case 4: 
    			numName = "fourth";
    			break;
    		case 5:
    			numName = "fifth";
    			break;
    		case 6: 
    			numName = "sixth";
    			break;
    		case 7:
    			numName = "seventh";
    			break;
    		case 8: 
    			numName = "eight";
    			break;
    		case 9:
    			numName = "ninth";
    			break;
    		case 10: 
    			numName = "tenth";
    			break;
    		default:
    			numName = intIn + (intIn<20?"th" : (intIn%10==1?"st":
    			(intIn%10==2?"nd":(intIn%10==3?"rd":"rh"))));
    		} //end Switch
     
    		return numName;
     
    	}
     
    } // end public class Midterm


  2. #2
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    Default Re: Help with Arrays

    Whew! So much to get done.
    I could not keep the instructions in my head long enough to read them all.

    The first thing needed here is a plan. Break all of this up into smaller problems, and work on just one at a time. The 'flow' of the program there looks like a great starting point, but some of those steps look like they could be broken down into smaller steps as well. The more you break the steps down, the more they start looking like code (or at least something that translates into code).

    I see a question about getting a loop done. I suggest making a loop that just prints hi. Then get it to print hi for the number of times entered by the user. Get that basic loop working and then start adding the code to do something inside the loop besides printing hi. Keep the additions small and test at every stage.

  3. #3
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    Default Re: Help with Arrays

    Alright, so I figured out 95% of it. I'm getting the code to output correctly. I have one method left to conquer.

    I have to write a method that grabs the input from the Average Grade and translate that into a letter grade. So, is it possible to get the return value from method averageGrade and put it into method letterGrade? I was also thinking doing an if statement to make it a letter grade. Let me know how this looks i.e.:

    public static String letterGrade(double averageGrade) {
     
    if (averageGrade > 89)
    letterGrade = "A";
    if (averageGrade > 79)
    letterGrade = "B";
    if (averageGrade > 69)
    letterGrade = "C";
    if (averageGrade > 59)
    letterGrade = "D";
    else
    letterGrade = "F";
     
    return = letterGrade;
     
     
     
    }
    Last edited by djhunt90; October 13th, 2012 at 12:37 PM.

  4. #4
    Super Moderator jps's Avatar
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    Default Re: Help with Arrays

    Quote Originally Posted by djhunt90 View Post
    Alright, so I figured out 95% of it. I'm getting the code to output correctly. I have one method left to conquer.

    I have to write a method that grabs the input from the Average Grade and translate that into a letter grade. So, is it possible to get the return value from method averageGrade and put it into method letterGrade? I was also thinking doing an if statement to make it a letter grade. Let me know how this looks i.e.:

    public static String letterGrade(double averageGrade) {
     
    if (averageGrade > 89)
    letterGrade = "A";
    if (averageGrade > 79)
    letterGrade = "B";
    if (averageGrade > 69)
    letterGrade = "C";
    if (averageGrade > 59)
    letterGrade = "D";
    else
    letterGrade = "F";
     
    return = letterGrade;
     
     
     
    }
    First let me say this is not to brush you off, but to get you thinking on the right path.
    Did you try it? Did it compile and run without errors? Are the results good?
    If so, great. If not, what seems to be wrong?

  5. #5
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    Default Re: Help with Arrays

    I changed it up a little:

    public static char letterGrade (double arrayIn[]) {
     
    		double abc = 0;
    		for(int i = 0;i < arrayIn.length;i++) {
    			abc += arrayIn[i];
     
    	} // end for
    		if (abc > 90)
    			return 'A';
    		if (abc > 80)
    			return 'B';
    		if (abc > 70)
    			return 'C';
    		if (abc > 60)
    			return 'D';
    		else 
    			return 'F';
    	}

    It's returning A for every one though. Is it because I'm use the arrayIn.length so it's pushing the highest to the top?

  6. #6
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    Default Re: Help with Arrays

    I actually believe I just answered my own question!

  7. #7
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    Default Re: Help with Arrays

    Just looking at your letterGrade method, it seems you are just adding up the grades in the array, not getting the average of the grades, which would mean that their grade should most definitely be higher than an 89.

  8. #8
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    Default Re: Help with Arrays

    Could you please post your final solution. It may help someone out with future questions. Thanks!

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