I need help commenting on the codes below:

Code 1

import java.io.BufferedReader; import java.io.FileNotFoundException; import java.io.FileReader; import java.io.IOException; import java.util.ArrayList; import java.util.Arrays; import java.util.List;

public class PreferenceData {

private final List students; private final List projects; private int[][] preferences;

private static enum ReadState { STUDENT_MODE, PROJECT_MODE, PREFERENCE_MODE, UNKNOWN; };

public PreferenceData() { super(); this.students = new ArrayList(); this.projects = new ArrayList(); }

public void addStudent(Student s) { this.students.add(s); }

public void addStudent(String s) { this.addStudent(Student.createStudent(s)); }

public void addProject(Project p) { this.projects.add(p); } public void addProject(String p) { this.addProject(Project.createProject(p)); }

public void createPreferenceMatrix() { this.preferences = new int[this.students.size()][this.projects.size()]; }

public void setPreference(Student s, Project p, int preference) { this.preferences[this.students.indexOf(s)][this.projects.indexOf(p)] = preference; }

public void setPreference(int row, int column, int preference) { this.preferences[row][column] = preference; }

public void setPreferenceRow(int row, String[] prefValues) { for (int j = 0; j < prefValues.length; j++) { this.preferences[row][j] = Integer.parseInt(prefValues[j]); } }

public List getStudents() { return students; }

public List getProjects() { return projects; }

public int[][] getPreferences() { return preferences; }

@Override public String toString() { return "PreferenceData [students=" + students + ", projects=" + projects + ", preferences=" + Arrays.toString(preferences) + "]"; }

static PreferenceData readData(String inputFile) {

PreferenceData prefs = new PreferenceData(); try(BufferedReader reader = new BufferedReader(new FileReader(inputFile))) { ReadState state = ReadState.UNKNOWN; int row = 0;

while (reader.ready()) { String line = reader.readLine(); switch (line.trim()) { case "Students:": state = ReadState.STUDENT_MODE; break; case "Projects:": state = ReadState.PROJECT_MODE; break; case "Preferences:": prefs.createPreferenceMatrix(); state = ReadState.PREFERENCE_MODE; break; default: switch (state) { case STUDENT_MODE: prefs.addStudent(line); break; case PROJECT_MODE: prefs.addProject(line); break; case PREFERENCE_MODE: prefs.setPreferenceRow(row, line.split(",")); row++; break; default: throw new PreferenceFormatException(line); } }

}

reader.close();

} catch (FileNotFoundException e) { System.err.println("Error opening preferences file. File does not exist as specified."); e.printStackTrace(); } catch (IOException e) { System.err.println("Error reading from file."); e.printStackTrace(); } catch (PreferenceFormatException e) { System.err.println("Preference file in incorrect format. I can't tell which section I'm in."); System.err.println("Line being read: " + e.getCurrentLine()); e.printStackTrace(); }

return prefs; }

public int getPreference(int i, int j) { return this.preferences[i][j]; } public int numStudents() { return this.students.size(); } public int numProjects() { return this.projects.size(); }

}

Code 2

import java.io.BufferedWriter; import java.io.FileWriter; import java.io.IOException; import java.util.ArrayList; import java.util.Arrays; import java.util.List;

import ilog.concert.IloException; import ilog.concert.IloIntVar; import ilog.concert.IloRange; import ilog.cplex.IloCplex;

public class Runner {

private static final String INPUT_FILE_NAME = "prefs.csv"; private static final String OUTPUT_FILE_NAME = "assignment.txt";

public static void main(String[] args) {

PreferenceData data = PreferenceData.readData(INPUT_FILE_NAME);

try(BufferedWriter writer = new BufferedWriter(new FileWriter(OUTPUT_FILE_NAME))) {

IloCplex cplex = new IloCplex(); cplex.setOut(null);

List variableNames = new ArrayList();

for (Student s : data.getStudents()) { for (Project p : data.getProjects()) { variableNames.add(s.getName() + ", " + s.getStudentNumber() + ", " + s.getEmail() + ", " + p.getSupervisor()); } } List variables = new ArrayList(variableNames.size());

for (String name : variableNames) variables.add(cplex.intVar(0, 1, name));

IloIntVar[] varArray = variables.toArray(new IloIntVar[variables.size()]); IloRange[] constraints = new IloRange[data.numStudents() + data.numProjects()]; for (int k = 0; k < data.numStudents(); k++) { IloIntVar[] studentVars = Arrays.copyOfRange(varArray, k * data.numProjects(), (k+1)*data.numProjects()); constraints[k] = cplex.addEq(1, cplex.sum(studentVars)); } for (int k = data.numStudents(); k < data.numStudents() + data.numProjects(); k++) { IloIntVar[] projectVars = new IloIntVar[data.numStudents()]; int column = k - data.numStudents(); for (int i = 0; i < data.numStudents(); i++) { projectVars[i] = varArray[i*data.numProjects() + column]; } constraints[k] = cplex.addLe(cplex.sum(projectVars), data.getProjects().get(column).getCapacity()); } int[] coefficients = new int[data.numStudents() * data.numProjects()]; for (int i = 0; i < data.numStudents(); i++) { for (int j = 0; j < data.numProjects(); j++) { coefficients[i * data.numProjects() + j] = data.getPreference(i, j); } } cplex.addMinimize(cplex.scalProd(varArray, coefficients)); List solution = null;

if (cplex.solve()) {

double[] values = cplex.getValues(varArray);

solution = new ArrayList();

for (int i = 0; i < varArray.length; i++) {

if (1.0 - values[i] < 0.00000001) {

solution.add(variableNames.get(i));

}

}

} for (String s : solution) { writer.write(s + " "); }

cplex.clearModel();

} catch (IloException e) { e.printStackTrace(); } catch (IOException e) { System.err.println("Failed attempt to write to file: " + OUTPUT_FILE_NAME); e.printStackTrace(); }

}

}