ClassPerformance.java

import java.util.List;

/**
 * Created with IntelliJ IDEA.
 * User: ayato
 * Date: 5/24/14
 * Time: 4:22 PM
 * To change this template use File | Settings | File Templates.
 */
public class ClassPerformance {

    enum Subjects {
        ENGLISH, MATH, JAPANESE
    }

    private final String className;
    private final List<Performance> performances;

    private int english;
    private int math;
    private int japanese;

    public ClassPerformance(String className, List<Performance> performances) {
        this.className = className;
        this.performances = performances;

        english = averageCalculate(Subjects.ENGLISH);
        math = averageCalculate(Subjects.MATH);
        japanese = averageCalculate(Subjects.JAPANESE);
    }

    private int averageCalculate(Subjects subject) {
        int sum = 0;
        switch (subject) {
            case ENGLISH:
                for (Performance performance : performances) {
                    sum += performance.english;
                }
                return sum / performances.size();
            case MATH:
                for (Performance performance : performances) {
                    sum += performance.math;
                }
                return sum / performances.size();
            case JAPANESE:
                for (Performance performance : performances) {
                    sum += performance.japanese;
                }
                return sum / performances.size();
            default:
                return 0;
        }
    }


    @Override
    public String toString() {
        return className + "\t" + english + "\t" + math + "\t" + japanese;
    }
}

Main.java

import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.*;

/**
 * Created with IntelliJ IDEA.
 * User: ayato
 * Date: 5/24/14
 * Time: 2:41 PM
 * To change this template use File | Settings | File Templates.
 */
public class Main {
    public static void main(String[] args) {
        List<Performance> performances = new ArrayList();
        List<String> classList = new ArrayList();

        List<String> lines = fileRead();
        for (String line : lines) {
            String[] params = line.split(", ");
            performances.add(new Performance(params));

            String className = params[0];
            if (!classList.contains(className)){
                classList.add(className);
            }
        }

        Collections.sort(classList);

        List<ClassPerformance> classPerformances = new ArrayList();
        for (String className : classList) {
            classPerformances.add(new ClassPerformance(className, pickClassPerformances(performances, className)));
        }

        System.out.println("クラス\t英語\t数学\t国語");
        System.out.println("--------------------------------");
        for (ClassPerformance classPerformance : classPerformances) {
            System.out.println(classPerformance);
        }

    }

    private static List<String> fileRead() {
        List<String> list = null;
        try {
            list = Files.readAllLines(Paths.get("performances.csv"), StandardCharsets.UTF_8);
        } catch (IOException e) {
            e.printStackTrace();  //To change body of catch statement use File | Settings | File Templates.
        }
        return list;
    }

    private static List<Performance> pickClassPerformances(List<Performance> performances, String className) {
        List<Performance> classPerformances = new ArrayList();
        for (Performance performance : performances) {
            if (className.equals(performance.className)) {
                classPerformances.add(performance);
            }
        }
        return classPerformances;
    }
}

Performance.java

/**
 * Created with IntelliJ IDEA.
 * User: ayato
 * Date: 5/24/14
 * Time: 2:43 PM
 * To change this template use File | Settings | File Templates.
 */
public class Performance {
    public final String className;
    public final int number;
    public final String name;
    public final int english;
    public final int math;
    public final int japanese;
    
    public Performance(String className, int number, String name, int english, int math, int japanese) {
        this.className = className;
        this.number = number;
        this.name = name;
        this.english = english;
        this.math = math;
        this.japanese = japanese;
    }

    public Performance(String[] params) {
        if(params == null || params.length != 6) throw new IndexOutOfBoundsException();
        this.className = params[0];
        this.number = Integer.parseInt(params[1]);
        this.name = params[2];
        this.english = Integer.parseInt(params[3]);
        this.math = Integer.parseInt(params[4]);
        this.japanese = Integer.parseInt(params[5]);
    }

    @Override
    public String toString() {
        return className + ", " + number + ", " + name;
    }
}