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Arrays: Comparing one array to another to find averages

Hey I'm trying to calculate the of a quiz by comparing two arrays. The two arrays set up are the correct answers and student answers of a quiz. I'm trying to get it to look like this:
Student Marks Average
Arnie Score: 4 Percentage: 0.8
This is because Arnie has got 4 questions correct out of 5 questions. The answers of the student and the correct answers are found in the text document which I already loaded onto an array on my code. The text document contains a 2D array with Arnie's answers in the form of chars and a 1D array containing the correct answers (also chars). There are more students but I would like some guidance on how to get the average for Arnie so I can do it for the rest of the names on my own.
Here is my code so far with the two arrays set up.
public class workingCode
{
private static String newline = System.getProperty("line.separator");
public static void stuAnsOut(String arg []) throws IOException
{
File studentAns = new File("Ans_Stu.txt");
Scanner stuAns = new Scanner(studentAns);
String stuAnsString[] = new String[6];
char stuAnsArray[][] = new char[3][5];
String[] stuNameArray = new String[3];
for (int i = 0; i<stuAnsString.length;i++)
{
stuAnsString[i]=stuAns.nextLine();
}
for (int i=0,j=0; i<stuAnsArray.length && j<stuAnsString.length;i++, j=j+2)
{
stuNameArray[i] = stuAnsString[j];
}
for (int i=0,j=1; i<stuAnsArray.length && j<stuAnsString.length;i++, j=j+2)
{
stuAnsArray[i] = stuAnsString[j].toUpperCase().toCharArray();
}
System.out.println("Student Answers: ");
System.out.printf("%5s","Name");
for (int i =0; i<1;i++)
{
for (int j =1; j<(stuAnsArray[i].length+1);j++)
{
System.out.printf("%5s",j);
}
}
System.out.printf("%n");
for (int i =0; i<stuAnsArray.length;i++)
{
System.out.printf("%5s",stuNameArray[i]);
for (int j=0;j<stuAnsArray[i].length;j++)
{
System.out.printf("%5s",stuAnsArray[i][j]);
}
System.out.printf("%n");
}
}
public static void corAnsOut(String arg []) throws IOException
{
File correctAns = new File("Ans_Cor.txt");
Scanner corAns = new Scanner(correctAns);
String corAnsString = corAns.next();
char corAnsArray[] = new char[5];
for (int i=0; i<corAnsArray.length;i++)
{
corAnsArray[i] = corAnsString.toUpperCase().charAt(i);
}
System.out.println("Correct Answers: ");
System.out.println(newline);
for (int i =1; i<(corAnsArray.length+1);i++)
{
System.out.printf("%5s",i);
}
System.out.printf("%n");
for (int i =0; i<corAnsArray.length;i++)
{
System.out.printf("%5s",corAnsArray[i]);
}
System.out.printf("%n");
}
}
I am not allowed to use ArrayLists, only Arrays. And please use the array names I already have in my code. Thanks!
Edit: This is what I got so far. But it is giving me an error:
public static void compareInteger(int corAnsArray [], int stuAnsArray[])
{double score =0;
for (int i = 0; i < stuAnsArray.length; i++)
{if(stuAnsArray[i] == corAnsArray[i])
score += 1.0;
}
System.out.println(score/corAnsArray.length);
}

What i would do is create a class called Student
public class Student {
private string studentName;
private float marks;
private float average;
// Getters & all parameter constructor
}
Then change your working class to
public class workingCode
{
private static String newline = System.getProperty("line.separator");
public static void stuAnsOut(String arg []) throws IOException
{
File studentAns = new File("Ans_Stu.txt");
Scanner stuAns = new Scanner(studentAns);
List<Student> students = new ArrayList<Student>();
while(stuAns.hasNext()) {
string parts = stuAns.nextLine().split(" ");
students.add(new Student(parts[0],parts[1],parts[2]))
}
// At this point you have all the students in the List
}
}
Now to calculate avg :
float total = 0;
for(Student s : students) {
total += s.getMarks();
}
System.out.println("avg = " + total/students.size());
or
float total = 0;
for(Student s : students) {
total += s.getAverage();
}
System.out.println("avg = " + total);

Code for comparing arrays (both for INT and String arrays):
public class Compare{
public static void main(String[] args){
double averageInt;
double averageString;
int[] correctInt = {9,8,12,6,3,12,90}; //Correct answers
int[] answerInt = {9,8,4,6,3,12,90}; //Student's answers
String[] correctString = {"A","A","B","C"}; //Correct answers
String[] answerString = {"A","C","B","C"}; //Student's answers
Compare compare = new Compare();
averageInt = compare.compareInteger(correctInt, answerInt);
averageString = compare.compareString(correctString, answerString);
System.out.println(averageInt);
System.out.println(averageString);
}
public double compareInteger(int[] correct, int[] answer){ //Compares the int arrays
double score = 0;
for(int i = 0; i < correct.length; i++){
if(correct[i] == answer[i])
score += 1.0;
}
return score/correct.length; //Returns average
}
public double compareString(String[] correct, String[] answer){ //Compares the String arrays
double score = 0;
for(int i = 0; i < correct.length; i++){
if(correct[i].equals(answer[i]))
score += 1.0;
}
return score/correct.length; //Returns average
}
}
I do not understand the marking system though. If you'd explain it more in-depth, I'd be more than happy to provide you with the code.

Altering the value of k in kNN algorithm - Java

I have applied the KNN algorithm for classifying handwritten digits. the digits are in vector format initially 8*8, and stretched to form a vector 1*64..
As it stands my code applies the kNN algorithm but only using k = 1. I'm not entirely sure how to alter the value k after attempting a couple of things I kept getting thrown errors. If anyone could help push me in the right direction it would be really appreciated. The training dataset can be found here and the validation set here.
ImageMatrix.java
import java.util.*;
public class ImageMatrix {
private int[] data;
private int classCode;
private int curData;
public ImageMatrix(int[] data, int classCode) {
assert data.length == 64; //maximum array length of 64
this.data = data;
this.classCode = classCode;
}
public String toString() {
return "Class Code: " + classCode + " Data :" + Arrays.toString(data) + "\n"; //outputs readable
}
public int[] getData() {
return data;
}
public int getClassCode() {
return classCode;
}
public int getCurData() {
return curData;
}
}
ImageMatrixDB.java
import java.util.*;
import java.io.*;
import java.util.ArrayList;
public class ImageMatrixDB implements Iterable<ImageMatrix> {
private List<ImageMatrix> list = new ArrayList<ImageMatrix>();
public ImageMatrixDB load(String f) throws IOException {
try (
FileReader fr = new FileReader(f);
BufferedReader br = new BufferedReader(fr)) {
String line = null;
while((line = br.readLine()) != null) {
int lastComma = line.lastIndexOf(',');
int classCode = Integer.parseInt(line.substring(1 + lastComma));
int[] data = Arrays.stream(line.substring(0, lastComma).split(","))
.mapToInt(Integer::parseInt)
.toArray();
ImageMatrix matrix = new ImageMatrix(data, classCode); // Classcode->100% when 0 -> 0% when 1 - 9..
list.add(matrix);
}
}
return this;
}
public void printResults(){ //output results
for(ImageMatrix matrix: list){
System.out.println(matrix);
}
}
public Iterator<ImageMatrix> iterator() {
return this.list.iterator();
}
/// kNN implementation ///
public static int distance(int[] a, int[] b) {
int sum = 0;
for(int i = 0; i < a.length; i++) {
sum += (a[i] - b[i]) * (a[i] - b[i]);
}
return (int)Math.sqrt(sum);
}
public static int classify(ImageMatrixDB trainingSet, int[] curData) {
int label = 0, bestDistance = Integer.MAX_VALUE;
for(ImageMatrix matrix: trainingSet) {
int dist = distance(matrix.getData(), curData);
if(dist < bestDistance) {
bestDistance = dist;
label = matrix.getClassCode();
}
}
return label;
}
public int size() {
return list.size(); //returns size of the list
}
public static void main(String[] argv) throws IOException {
ImageMatrixDB trainingSet = new ImageMatrixDB();
ImageMatrixDB validationSet = new ImageMatrixDB();
trainingSet.load("cw2DataSet1.csv");
validationSet.load("cw2DataSet2.csv");
int numCorrect = 0;
for(ImageMatrix matrix:validationSet) {
if(classify(trainingSet, matrix.getData()) == matrix.getClassCode()) numCorrect++;
} //285 correct
System.out.println("Accuracy: " + (double)numCorrect / validationSet.size() * 100 + "%");
System.out.println();
}

In the for loop of classify you are trying to find the training example that is closest to a test point. You need to switch that with a code that finds K of the training points that is the closest to the test data. Then you should call getClassCode for each of those K points and find the majority(i.e. the most frequent) of the class codes among them. classify will then return the major class code you found.
You may break the ties (i.e. having 2+ most frequent class codes assigned to equal number of training data) in any way that suits your need.
I am really inexperienced in Java, but just by looking around the language reference, I came up with the implementation below.
public static int classify(ImageMatrixDB trainingSet, int[] curData, int k) {
int label = 0, bestDistance = Integer.MAX_VALUE;
int[][] distances = new int[trainingSet.size()][2];
int i=0;
// Place distances in an array to be sorted
for(ImageMatrix matrix: trainingSet) {
distances[i][0] = distance(matrix.getData(), curData);
distances[i][1] = matrix.getClassCode();
i++;
}
Arrays.sort(distances, (int[] lhs, int[] rhs) -> lhs[0]-rhs[0]);
// Find frequencies of each class code
i = 0;
Map<Integer,Integer> majorityMap;
majorityMap = new HashMap<Integer,Integer>();
while(i < k) {
if( majorityMap.containsKey( distances[i][1] ) ) {
int currentValue = majorityMap.get(distances[i][1]);
majorityMap.put(distances[i][1], currentValue + 1);
}
else {
majorityMap.put(distances[i][1], 1);
}
++i;
}
// Find the class code with the highest frequency
int maxVal = -1;
for (Entry<Integer, Integer> entry: majorityMap.entrySet()) {
int entryVal = entry.getValue();
if(entryVal > maxVal) {
maxVal = entryVal;
label = entry.getKey();
}
}
return label;
}
All you need to do is adding K as a parameter. Keep in mind, however, that the code above does not handle ties in a particular way.

Array (list?) required, but int found error

I have the following code:
import java.util.ArrayList;
public class TestCandidate2
{
public static void main(String[] args) {
ArrayList<Candidate> election = new ArrayList<Candidate>();
Candidate john = new Candidate("John Smith", 5000);
election.add(john);
Candidate mary = new Candidate("Mary Miller", 4000);
election.add(mary);
Candidate michael = new Candidate("Micheal Duffy", 6000);
election.add(michael);
Candidate tim = new Candidate("Tim Robinson", 2500);
election.add(tim);
Candidate joe = new Candidate("Joe Ashtony", 1800);
election.add(joe);
System.out.println("Results Per Candidate:");
System.out.println("________________________");
System.out.print("\n");
int totalVotes = 0;
int total = 0;
for(Candidate dec : election) {
System.out.println(dec.toString());
total += dec.getVotes();
totalVotes += dec.getVotes();
}
System.out.print("\n");
System.out.println("Total number of votes in election: " + totalVotes);
}
public static void printVotes(ArrayList<Candidate> table) {
for(int i = 0; i < table.size(); i++) {
System.out.println(table.size()[i]);
}
}
/**public static int getTotal(ArrayList<Candidate> table) {
int total = 0;
for(int i = 0; i < table.size(); i++) {
total = table[i].getVotes() + total;
}
return total;
}*/
/**public static void printResults(ArrayList<Candidate> table) {
double total = getTotal(table);
System.out.print("Candidate Votes Received % of Total Votes");
System.out.print("\n");
for(int i = 0; i < table.length; i++) {
System.out.printf("%s %17d %25.0f", table[i].getName(), table[i].getVotes(), ((table[i].getVotes() / total) * 100));
System.out.println("");
}
}*/
}
Now first off the error I think I should be getting is 'arraylist required, but int found', but instead the error that I am getting is 'array required, but int found'.
I do not know how I should fix the int i, for whenever I put [] to declare it as an array I still get errors. I have tried researching, but no one seems to have my exact problem.

You appear to be accessing your Lists incorrectly. Instead of:
table[i].getVotes()
try:
table.get(i).getVotes();
Or avoid using indexes altogether. For example, you could rewrite getTotal() as:
public static int getTotal(List<Candidate> candidates) {
int total = 0;
foreach (Candidate c : candidates) {
total += c.getVotes();
}
return total;
}
The line producing the error:
System.out.println(table.size()[i]);
is a little confusing, but I think you want:
System.out.println(table.get(i).getVotes());

You could use List.get(int) to get an element by position (not [] that's for arrays). Also, I suggest you program to the list interface. Like
public static void printVotes(List<Candidate> table) {
for(int i = 0; i < table.size(); i++) {
System.out.println(table.get(i));
}
}
You could also use a for-each loop and += like,
public static int getTotal(List<Candidate> table) {
int total = 0;
for(Candidate c : table) {
total += c.getVotes();
}
return total;
}

you should use table.get(i) instead of table[i]. this is an ArrayList not an array

recursive method not properly executing

I have a programming assignment for an introductory level Java class (the subset sum problem) - for some reason, my recursive method isn't executing properly (it just goes straight to the end of the method and prints out the sorted list). Any help would be appreciated - I'm a newbie and recursive functions are really confusing to me.
package programmingassignment3;
import java.io.*;
import java.util.*;
public class ProgrammingAssignment3 {
static int TARGET = 10;
static ArrayList<Integer> list = new ArrayList<>();
static int SIZE = list.size();
public static void main(String[] args) {
populateSortSet();
sumInt(list);
recursiveSS(list);
}//main
public static void populateSortSet() {
try {
File f = new File("set0.txt");
Scanner input = new Scanner(f);
while (input.hasNext()) {
int ele = input.nextInt();
if (ele < TARGET && !list.contains(ele)) {
list.add(ele);
}//if
}//while
Collections.sort(list);
}//try
catch (IOException e) {
e.printStackTrace();
}//catch
}//populateSet
public static void recursiveSS(ArrayList<Integer> Alist) {
if (Alist.size() == SIZE) {
if (sumInt(Alist) == TARGET) {
System.out.println("The integers that equal " + TARGET + "are: " + Alist);
} //if==TARGET
}//if==SIZE
else {
for (int i = 0; i < SIZE; i++) {
ArrayList<Integer> list1 = new ArrayList<>(Alist);
ArrayList<Integer> list0 = new ArrayList<>(Alist);
list1.add(1);
list0.add(0);
if (sumInt(list0) < TARGET) {
recursiveSS(list0);
}//if
if (sumInt(list1) < TARGET) {
recursiveSS(list1);
}//if
}//for
}//else
System.out.println("echo" + Alist);
}//recursiveSS
public static int sumInt(ArrayList<Integer> Alist) {
int sum = 0;
for (int i = 0; i < SIZE - 1; i++) {
sum += Alist.get(i);
}//for
if (Alist.size() == TARGET) {
sum += Alist.get(Alist.size() - 1);
}//if
return sum;
}//sumInt
}//class

This thing that you do at class level:
static ArrayList<Integer> list = new ArrayList<>();
static int SIZE = list.size();
means that SIZE will be initiated to 0, and stay 0 (even if you add elements to the list.)
This means that the code inside the for-loop will be executed 0 times.
Try something like:
public class ProgrammingAssignment3 {
private static int initialSize;
//...
public static void populateSortSet() {
//populate the list
initialSize = list.size();
}
So you don't set the value of the size variable until the list is actually populated.
That being said, there a quite a few other strange things in your code, so I think you need to specify exactly what you are trying to solve here.

Here's how I'd do it. I hope it clarifies the stopping condition and the recursion. As you can see, static methods are not an issue:
import java.util.ArrayList;
import java.util.List;
/**
* Demo of recursion
* User: mduffy
* Date: 10/3/2014
* Time: 10:56 AM
* #link http://stackoverflow.com/questions/26179574/recursive-method-not-properly-executing?noredirect=1#comment41047653_26179574
*/
public class RecursionDemo {
public static void main(String[] args) {
List<Integer> values = new ArrayList<Integer>();
for (String arg : args) {
values.add(Integer.valueOf(arg));
}
System.out.println(String.format("input values : %s", values));
System.out.println(String.format("iterative sum: %d", getSumUsingIteration(values)));
System.out.println(String.format("recursive sum: %d", getSumUsingRecursion(values)));
}
public static int getSumUsingIteration(List<Integer> values) {
int sum = 0;
if (values != null) {
for (int value : values) {
sum += value;
}
}
return sum;
}
public static int getSumUsingRecursion(List<Integer> values) {
if ((values == null) || (values.size() == 0)) {
return 0;
} else {
if (values.size() == 1) { // This is the stopping condition
return values.get(0);
} else {
return values.get(0) + getSumUsingRecursion(values.subList(1, values.size())); // Here is recursion
}
}
}
}
Here is the case I used to test it:
input values : [1, 2, 3, 4, 5, 6]
iterative sum: 21
recursive sum: 21
Process finished with exit code 0

Thanks everyone. I really appreciate the help. I did figure out the problem and the solution is as follows (closing brace comments removed for the reading pleasure of #duffymo ):
public class ProgrammingAssignment3 {
static int TARGET = 6233;
static ArrayList<Integer> set = new ArrayList<>();
static int SIZE;
static int count = 0;
public static void populateSortSet() {
try {
File f = new File("set3.txt");
Scanner input = new Scanner(f);
while (input.hasNext()) {
int ele = input.nextInt();
if (ele < TARGET && !set.contains(ele)) {
set.add(ele);
}
}
Collections.sort(set);
SIZE = set.size();
System.out.println("The original sorted set: " + set + "\t subset sum = " + TARGET);
}
catch (IOException e) {
e.printStackTrace();
}
}
public static void recursiveSS(ArrayList<Integer> list) {
if (list.size() == SIZE) {
if (sumInt(list) == TARGET) {
System.out.print("The Bit subset is: " + list + "\t");
System.out.println("The subset is: " + getSubset(list));
count++;
}
}
else {
ArrayList<Integer> list1 = new ArrayList<>(list);//instantiate list1
ArrayList<Integer> list0 = new ArrayList<>(list);//instantiate list0
list1.add(1);
list0.add(0);
if (sumInt(list0) <= TARGET) {
recursiveSS(list0);
}
if (sumInt(list1) <= TARGET) {
recursiveSS(list1);
}
}
}
public static int sumInt(ArrayList<Integer> list) {
int sum = 0;
for (int i = 0; i < list.size(); i++) {
if (list.get(i) == 1) {
sum += set.get(i);
}
}
return sum;
}
public static ArrayList<Integer> getSubset(ArrayList<Integer> list) {
ArrayList<Integer> l = new ArrayList<>();
for (int i = 0; i < list.size(); i++) {
if (list.get(i) == 1) {
l.add(set.get(i));
}
}
return l;
}
}

IndexOutOfBoundsException while accessing List

I'm working on a project for a class, and I think I've got it mostly figured out, but it keeps giving me different Exception errors and now I'm stumped.
The instructions can be found here: http://www.cse.ohio-state.edu/cse1223/currentsem/projects/CSE1223Project11.html
Here is the code I have thus far, currently giving me and IndexOutOfBounds exception in the getMaximum method.
Any help would be much appreciated.
import java.io.*;
import java.util.*;
public class Project11a {
public static void main(String[] args) throws FileNotFoundException {
Scanner keyboard = new Scanner(System.in);
System.out.print("Enter an input file name: ");
String fileName = keyboard.nextLine();
Scanner in = new Scanner(new File(fileName));
System.out.print("Enter an output file name: ");
String outFile = keyboard.nextLine();
PrintWriter outputFile = new PrintWriter(outFile);
while (in.hasNextLine()) {
String name = in.nextLine();
List<Integer> series = readNextSeries(in);
int mean = getAverage(series);
int median = getMedian(series);
int max = getMaximum(series);
int min = getMinimum(series);
outputFile.printf("%-22s%6d%n", name, mean, median, max, min);
}
in.close();
outputFile.close();
}
// Given a Scanner as input read in a list of integers one at a time until a
// negative
// value is read from the Scanner. Store these integers in an
// ArrayList<Integer> and
// return the ArrayList<Integer> to the calling program.
private static List<Integer> readNextSeries(Scanner inScanner) {
List<Integer> nextSeries = new ArrayList<Integer>();
while (inScanner.hasNextInt()) {
int currentLine = inScanner.nextInt();
if (currentLine != -1) {
nextSeries.add(currentLine);
} else {
break;
}
}
return nextSeries;
}
// Given a List<Integer> of integers, compute the median of the list and
// return it to
// the calling program.
private static int getMedian(List<Integer> inList) {
Collections.sort(inList);
int middle = inList.size() / 2;
int median = -1;
if (inList.size() % 2 == 1) {
median = inList.get(middle);
} else {
try {
median = (inList.get(middle - 1) + inList.get(middle)) / 2;
} catch (Exception e) {
}
}
return median;
}
// Given a List<Integer> of integers, compute the average of the list and
// return it to
// the calling program.
private static int getAverage(List<Integer> inList) {
int average = 0;
if (inList.size() == 0) {
return 0;
}
for (int i = 0; i < inList.size(); i++) {
average += inList.get(i);
}
return (average / inList.size());
}
// Given a List<Integer> of integers, compute the maximum of the list and
// return it to
// the calling program.
private static int getMaximum(List<Integer> inList) {
int max = inList.get(0);
for (int i = 1; i < inList.size(); i++) {
if (inList.get(i) > max) {
max = inList.get(i);
}
}
return max;
}
// Given a List<Integer> of integers, compute the maximum of the list and
// return it to
// the calling program.
private static int getMinimum(List<Integer> inList) {
int min = inList.get(0);
for (int i = 1; i < inList.size(); i++) {
if (inList.get(i) < min) {
min = inList.get(i);
}
}
return min;
}
}

Seemed like that your list is empty.
What can triggered the exception is the statement:
int max = inList.get(0);
So your inList do not have the value in the first index,which means the inList is empty.