We Keep Coding

Accuracy of Multi Layer Neural Network using Backpropagation around 86% normal?

Recently, I started trying to train a neural network using backpropagation. The network structure is 784-512-10, and I used the Sigmoid activation function. When I tested a single-layer network on the MNIST dataset, I got around 90%. My results are around 86% with this multi-layer network, is this normal? Did I get the backpropagation part wrong?
Here is my code:
import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.*;
import java.nio.file.Files;
import java.nio.file.StandardCopyOption;
import java.security.SecureRandom;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Random;
import java.util.Scanner;
public class NeuralNetwork{
public static double learningRate = 0.01;
public static int epoch = 15;
public static int ROWS = 28;
public static int COLUMNS = 28;
public static int INPUT = ROWS * COLUMNS;
public static int outNum = 10;
public static int hiddenNum = 512;
public static double[][] weights2 = new double[outNum][hiddenNum];
public static double[] bias2 = new double[outNum];
public static double[][] weights1 = new double[hiddenNum][INPUT];
public static double[] bias1 = new double[outNum];
private static final double TRAININGSIZE = 10;
public static double[][] inputs = new double[outNum][INPUT];
private static final double[][] target = new double[outNum][outNum];
private static final ArrayList<String> filenames = new ArrayList<>();
private static final ArrayList<Integer> yetDone = new ArrayList<>();
public static double[] actual = new double[outNum];
public static Random rand = new SecureRandom();
public static Scanner input = new Scanner(System.in);
public static void main(String[]args) throws Exception {
System.out.println("1. Learn the network");
System.out.println("2. Guess a number");
System.out.println("3. Guess file");
System.out.println("4. Guess All Numbers");
System.out.println("5. Guess image");
switch (input.nextInt()){
case 1:
learn();
break;
case 2:
guess();
break;
case 3:
guessFile();
break;
case 4:
guessAll();
break;
}
}
public static void guessAll() throws IOException, ClassNotFoundException {
System.out.println("Recognizing...");
/*
for(int x = 1; x < 60000; x++){
filenames.add("data/" + String.format("%05d",x) + ".txt");
}
ObjectInputStream ois = new ObjectInputStream(new BufferedInputStream(new FileInputStream("network.ser")));
Layers lay = (Layers) ois.readObject();
int correct = 0;
for (String z : filenames) {
double[] a = scan(z,0);
correct += getBestGuess(sigmoid(lay.step(a))) == actual[0] ? 1 : 0;
}
System.out.println("Training: " + correct + " / " + filenames.size() + " correct.");
filenames.clear();
*/
for(int x = 60000; x < 70000; x++){
filenames.add("data/" + String.format("%05d",x) + ".txt");
}
ObjectInputStream oiss = new ObjectInputStream(new BufferedInputStream(new FileInputStream("network1.ser")));
Layers lays1 = (Layers) oiss.readObject();
ObjectInputStream oiss2 = new ObjectInputStream(new BufferedInputStream(new FileInputStream("network2.ser")));
Layers lays2 = (Layers) oiss2.readObject();
int corrects = 0;
for (String z : filenames) {
double[] a = scan(z,0);
corrects += getBestGuess(sigmoid(lays2.step(sigmoid(lays1.step(a))))) == actual[0] ? 1 : 0;
}
System.out.println("Testing: " + corrects + " / " + filenames.size() + " correct.");
System.out.println("Done!");
}
public static void makeList(){
for(int index = 0; index < TRAININGSIZE; index++){
int indices = rand.nextInt(yetDone.size() - 1) + 1;
filenames.add("data/" + String.format("%05d",yetDone.get(indices)) + ".txt");
yetDone.remove(indices);
}
prepareData();
for(int indices = 0; indices < outNum; indices++) {
for(int index = 0; index < outNum; index++){
target[indices][index] = 0;
}
target[indices][(int)actual[indices]] = 1;
}
}
public static void prepareData(){
for(int index = 0; index < outNum; index++){
try {
inputs[index] = scan(filenames.get(index), index);
} catch (FileNotFoundException ex) {
ex.printStackTrace();
}
}
}
public static double[] scan(String filename, int index) throws FileNotFoundException {
Scanner in = new Scanner(new File(filename));
double[] a = new double[INPUT];
for(int i = 0; i < INPUT; i++){
a[i] = in.nextDouble() / 255;
}
actual[index] = in.nextDouble();
return a;
}
public static void guessFile() throws IOException, ClassNotFoundException {
System.out.print("Enter Filename: ");
double[] a = scan(input.next(), 0);
ObjectInputStream ois = new ObjectInputStream(new BufferedInputStream(new FileInputStream("network.ser")));
Layers lay = (Layers) ois.readObject();
double[] results = lay.step(a);
System.out.println("This is a " + getBestGuess(sigmoid(results)) + "!");
System.out.println(Arrays.toString(results));
}
public static double guess(double[] a) throws IOException, ClassNotFoundException {
ObjectInputStream ois = new ObjectInputStream(new BufferedInputStream(new FileInputStream("network.ser")));
Layers lay = (Layers) ois.readObject();
double[] results = lay.step(a);
return getBestGuess(sigmoid(results));
}
public static void guess() throws IOException, ClassNotFoundException {
ObjectInputStream ois = new ObjectInputStream(new BufferedInputStream(new FileInputStream("network.ser")));
System.out.println("Input number: ");
Layers lay = (Layers) ois.readObject();
double[] a = new double[INPUT];
for(int index = 0; index < a.length; index++){
a[index] = input.nextInt();
}
double[] results = lay.step(a);
System.out.println("This is a " + getBestGuess(sigmoid(results)) + "!");
System.out.println(Arrays.toString(sigmoid(results)));
}
public static void learn() {
System.out.println("Learning...");
initialise(weights2, outNum, hiddenNum);
initialise(bias2);
initialise(weights1,hiddenNum, INPUT);
initialise(bias1);
Layers lay2 = new Layers(weights2, bias2, outNum, hiddenNum);
Layers lay1 = new Layers(weights1, bias1, hiddenNum, INPUT);
double[] result2 = new double[lay2.outNum];
double[] result1 = new double[lay1.outNum];
double[] a2;
double[] a1;
double cost = 0;
double sumFinal;
for(int x = 0; x < epoch; x++) {
yetDone.clear();
for(int y = 0; y < 60000; y++){
yetDone.add(y);
}
for (int ind = 0; ind < 200; ind++) {
filenames.clear();
makeList();
for (int n = 0; n < lay2.outNum; n++) {
a1 = inputs[n]; //number
result1 = sigmoid(lay1.step(a1));
a2 = result1;
result2 = sigmoid(lay2.step(a2));
for (int i = 0; i < lay2.outNum; i++) {
for (int j = 0; j < lay2.INPUT; j++) {
weights2[i][j] += learningRate * a2[j] * (target[n][i] - result2[i]);
cost += Math.pow((target[n][i] - result2[i]), 2);
}
}
for(int i = 0; i < lay1.outNum; i++){
for(int j = 0; j < lay1.INPUT; j++){
sumFinal = 0;
for(int k = 0; k < lay2.outNum; k++){
// weight * derivSigma(outputHiddenLayer) * 2(out - expected)
sumFinal += result1[k] * (1 - result1[k]) * 2 * (result2[k] - target[n][k]); // * weights2[k][i]
}
weights1[i][j] -= learningRate * a1[j] * sumFinal * result1[i] * (1 - result1[i]);
}
}
}
lay1.update(weights1, bias1);
lay2.update(weights2, bias2);
}
System.out.println("Epoch " + x + ": " + cost);
cost = 0;
}
System.out.println(Arrays.toString(result1));
System.out.println(Arrays.toString(result2));
for(double[] arr : inputs) {
System.out.println("This is a " + getBestGuess(sigmoid(lay2.step(sigmoid(lay1.step(arr))))) + "!");
}
try (ObjectOutputStream oos = new ObjectOutputStream(new BufferedOutputStream(new FileOutputStream("network1.ser")))) {
oos.writeObject(lay1);
} catch (IOException ex) {
ex.printStackTrace();
}
try (ObjectOutputStream oos = new ObjectOutputStream(new BufferedOutputStream(new FileOutputStream("network2.ser")))) {
oos.writeObject(lay2);
} catch (IOException ex) {
ex.printStackTrace();
}
System.out.println("Done! Saved to file.");
}
public static double sigmoid(double x){
return 1 / (1 + Math.exp(-x));
}
public static double[] sigmoid(double[] weights){
for(int index = 0; index < weights.length; index++){
weights[index] = sigmoid(weights[index]);
}
return weights;
}
public static void initialise(double[] bias){
Random random = new Random();
for(int index = 0; index < bias.length; index++){
bias[index] = random.nextGaussian();
}
}
public static void initialise(double[][] weights, int outNum, int INPUT){
Random random = new Random();
for(int index = 0; index < outNum; index++){
for(int indice = 0; indice < INPUT; indice++){
weights[index][indice] = random.nextGaussian();
}
}
}
public static int getBestGuess(double[] result){
double k = Integer.MIN_VALUE;
double index = 0;
int current = 0;
for(double a : result){
if(k < a){
k = a;
index = current;
}
current++;
}
return (int)index;
}
}
class Layers implements Serializable {
private static final long serialVersionUID = 8L;
double[][] weights;
double[] bias;
int outNum;
int INPUT;
public Layers(double[][] weights, double[] bias, int outNum, int INPUT){
this.weights = weights;
this.bias = bias;
this.outNum = outNum;
this.INPUT = INPUT;
}
public void update(double[][] weights, double[] bias){
this.weights = weights;
this.bias = bias;
}
public double[] step(double[] aa){
double[] out = new double[outNum];
for (int index = 0; index < outNum; index++) {
for (int indices = 0; indices < INPUT; indices++) {
out[index] += weights[index][indices] * aa[indices];
}
}
return out;
}
}
Thanks in advance!

How can I take the length from the text files in java?

I am new in java. Firstly, I'm sorry for my English. I wrote a code to merge two different txt files in the mergedFile.txt with determined data from the data1.txt and data2.txt. I create 5 different arrays to use them better but I cannot learn the length of words in the textfiles so arrays are using determined parameter. If I want to add another student, this codes don't work. Can you help me?
data1.txt
ID,Name,LastName,Department
12345,John,Samon,Computer Science
14524,David,Souza,Electric and Electronic
.
.
data2.txt
ID,Q1,Q2,Q3,Midterm,Final
12345,100,90,75,89,100
14524,80,70,65,15,90
.
margedFile.txt
ID,Name,Q_Average,Midterm,Final,Department
12345,John,88.3,89,100,Computer Science
14524,David,67.0,100,70,Electric and Electronic
This is ReadData Class
import java.io.FileInputStream;//import java.io library
import java.util.Scanner;//import scanner library
public class ReadData {
public static String[] Read(String filename,String filename2) {
Scanner scan = null;
Scanner scan1 = null;/
FileInputStream input1 = null;
FileInputStream input = null;
String[] result = new String[3];
try {
input = new FileInputStream(filename);
scan = new Scanner(input);
input1 = new FileInputStream(filename2);
scan1 = new Scanner(input1);
String[][] myArray = new String[4][4];
String[][] myArray1 = new String[4][6];
while(scan.hasNext() || scan1.hasNext()) {
for (int i = 0; i < myArray.length; i++) {
String[] split =
scan.nextLine().trim().split(",");
for (int j = 0; j < split.length; j++)
{
myArray[i][j] = split[j];
}
}
for (int i = 0; i < myArray1.length; i++) {
String[] split1 = scan1.nextLine().trim().split(",");
for (int j = 0; j < split1.length; j++) {
myArray1[i][j] = split1[j];
}
}
}
int[][] quiz = new int[3][3];
double[] average = new double[3];
int sum = 0;
double averagee = 0;
for (int i = 0; i < quiz.length; i++) {
for (int j = 0; j < quiz.length; j++) {
quiz[i][j] = Integer.parseInt(myArray1[i+1][j+1]);
sum += quiz[i][j];
}
averagee = sum/quiz.length;
average[i] = averagee;
sum = 0;
}
for (int i = 1; i < myArray1.length; i++) {
for (int j = 1; j < myArray1.length; j++) {
if(myArray[i][0].equalsIgnoreCase(myArray1[j][0])) {
result[i-1] = "\n" + myArray[i][0] + " "+ myArray[i][1] + " " + (average[j-1]) +" "+ myArray1[j][4] +" " + myArray1[j][5] + " "+ myArray[i][3];
//System.out.println(Arrays.deepToString(myArray[i]) + " " + Arrays.deepToString(myArray1[j]));
}
}
}
//System.out.println(Arrays.deepToString(quiz));
//System.out.println(Arrays.toString(average));
}
catch(Exception e) {
System.out.println(e);
}
return result;
}
}
This is WriteData class
import java.io.FileOutputStream;
import java.io.PrintWriter;
import java.util.Arrays;
public class WriteData extends ReadData {
void Write(String filename) {
PrintWriter writer = null;
FileOutputStream output = null;
try {
output = new FileOutputStream(filename);
writer = new PrintWriter(output);
writer.print("ID,Name,Q_Average,Midterm,Final,Department ");
writer.print(Arrays.toString(Read("data1.txt",
"data2.txt")));
writer.flush();
writer.close();
} catch (Exception e) {
// TODO: handle exception
}
}
}

How do I export the ArrayList to a CSV file

I have this code, it gets the average grade, but I need to export the arraylist Hell to a CSV file. How do I do this?
import java.util.*;
import java.io.*;
import java.io.PrintWriter;
import java.text.*;
public class hello3 {
public static void main(String[] args)
{
Scanner in = new Scanner(System.in);
System.out.printf("Please enter the name of the input file: ");
String input_name = in.next();
System.out.printf("Please enter the name of the output CSV file: ");
String csv_name = in.next();
System.out.printf("Please enter the name of the output pretty-print file: ");
String pretty_name = in.next();
processGrades(input_name, csv_name, pretty_name);
System.out.printf("\nExiting...\n");
}
public static void processGrades (String input_name, String csv_name, String pretty_name)
{
PrintWriter csv = null;
PrintWriter pretty = null;
String[][] data = readSpreadsheet(input_name);
boolean resultb = sanityCheck(data);
int length = data.length;
ArrayList<String> test_avg = new ArrayList<String>();
ArrayList<String> HW_avg = new ArrayList<String>();
ArrayList<String> NAME = new ArrayList<String>();
ArrayList<String> ColN = new ArrayList<String>();
ArrayList<String> Hell = new ArrayList<String>();
for(int row = 1; row<length; row++)
{
String name = data[row][0];
String name2 = data[row][1];
String Name = name+" "+name2;
int test1 = Integer.parseInt(data[row][2]);
int test2 = Integer.parseInt(data[row][3]);
int test3 = Integer.parseInt(data[row][4]);
int Test = (test1+test2+test3)/3;
String Testav = Integer.toString(Test);
int hw1 = Integer.parseInt(data[row][5]);
int hw2 = Integer.parseInt(data[row][6]);
int hw3 = Integer.parseInt(data[row][7]);
int hw4 = Integer.parseInt(data[row][8]);
int hw5 = Integer.parseInt(data[row][9]);
int hw6 = Integer.parseInt(data[row][10]);
int hw7 = Integer.parseInt(data[row][11]);
int HW = (hw1+hw2+hw3+hw4+hw5+hw6+hw7)/7;
int[] trying = {Test, HW};
int low = find_min(trying);
String grade = null;
if(low>=90)
{
grade ="A";
}
if(low < 90&& low>= 80)
{
grade = "B";
}
if(low <80&&low>=70)
{
grade ="C";
}
if(low<70&&low>=60)
{
grade="D";
}
if(low<60)
{
grade = "F";
}
String Lows = Integer.toString(low);
String HWav = Integer.toString(HW);
test_avg.add(Testav);
HW_avg.add(HWav);
NAME.add(Name);
Hell.add(Name);
Hell.add(Testav);
Hell.add(HWav);
Hell.add(Lows);
Hell.add(grade);
System.out.println(Hell);
System.out.printf("\n");
}
}
public static int find_min(int[] values)
{
int result = values[0];
for(int i = 0; i<values.length; i++)
{
if(values[i]<result)
{
result = values[i];
}
}
return result;
}
public static boolean sanityCheck(String[][] data)
{
if (data == null)
{
System.out.printf("Sanity check: nul data\n");
return false;
}
if(data.length<3)
{
System.out.printf("Sanity check: %d rows\n",data.length);
return false;
}
int cols= data[0].length;
for(int row = 0; row<data.length; row++)
{
int current_cols = data[row].length;
if(current_cols!=cols)
{
System.out.printf("Sanity Check: %d columns at rows%d\n", current_cols, row);
return false;
}
}
return true;
}
public static String[][] readSpreadsheet(String filename)
{
ArrayList<String> lines = readFile(filename);
if (lines == null)
{
return null;
}
int rows = lines.size();
String[][] result = new String[rows][];
for (int i = 0; i < rows; i++)
{
String line = lines.get(i);
String[] values = line.split(",");
result[i] = values;
}
return result;
}
public static ArrayList<String> readFile(String filename)
{
File temp = new File(filename);
Scanner input_file;
try
{
input_file = new Scanner(temp);
} catch (Exception e)
{
System.out.printf("Failed to open file %s\n",
filename);
return null;
}
ArrayList<String> result = new ArrayList<String>();
while (input_file.hasNextLine())
{
String line = input_file.nextLine();
result.add(line);
}
input_file.close();
return result;
}
}
Any help would be appreciated. thank you.

Broadly, you need to open a file with the name you require, and a writer in a loop - like this:
File csvFile = new File(csvName);
try (PrintWriter csvWriter = new PrintWriter(new FileWriter(csvFile));){
for(String item : list){
csvWriter.println(item);
}
} catch (IOException e) {
//Handle exception
e.printStackTrace();
}
Obviously you will have to print some commas as required

Array throws NullPointerException in Java

I have the following little problem... I have this code that uses the method OpenFile() of one class ReadData to read a .txt file and also I have another class ArraysTZones used to create an object that stores 3 arrays (data1,data2,data3) and 3 integers (total1,total2,total3) returned by the method OpenFile(). The problem is that when I try to display each array (data1,data2,data3) using the method getArray() of ArrayTZones it stops and displays the error NullPointerException. Anyone knows how could I fix this?
public static void main (String args[]) throws IOException {
String fileName = ".//data.txt";
int[] def = new int[180];
try {
ReadData file = new ReadData(fileName);
ArraysTZones summaryatz = new ArraysTZones();
summaryatz = file.OpenFile();
for (int i = 0; i < 180; i++)
System.out.print (summaryatz.getArray1()[i] + " ");
System.out.println ("");
System.out.println (summaryatz.getTotal1());
for (int i = 0; i < 180; i++)
System.out.print (summaryatz.getArray2()[i] + " ");
System.out.println ("");
System.out.println (summaryatz.getTotal2());
for (int i = 0; i < 180; i++)
System.out.print (summaryatz.getArray3()[i] + " ");
System.out.println ("");
System.out.println (summaryatz.getTotal3());
}
catch (IOException e) {
System.out.println(e.getMessage());
}
}
Heres OpenFile()
public ArraysTZones OpenFile() throws IOException {
FileReader reader = new FileReader(path);
BufferedReader textReader = new BufferedReader(reader);
int numberOfTimeZones = 3;
int[] data1 = new int[180];
int[] data2 = new int[180];
int[] data3 = new int[180];
int total1 = 0;
int total2 = 0;
int total3 = 0;
ArraysTZones atz = new ArraysTZones();
for (int i = 0; i < numberOfTimeZones; i++){
if (i == 0) {
String firstTimeZone = textReader.readLine();
String[] val = firstTimeZone.split ("\\s+");
for (int u = 0; u < val.length; u++)
{
int stats = (int)(Math.ceil(Math.abs(Double.parseDouble(val[u]))));
total1 += stats;
data1[u] = stats;
}
total1= total1/180;
atz.setTotal1(total1);
atz.setArray1(data1);
}
else
if (i == 1) {
String secondTimeZone = textReader.readLine();
String[] val = secondTimeZone.split ("\\s+");
for (int u = 0; u < val.length; u++)
{
int stats = (int)(Math.ceil(Math.abs(Double.parseDouble(val[u]))));
total2 += stats;
data2[u] = stats;
}
total2= total2/180;
atz.setTotal2(total2);
atz.setArray2(data2);
}
else {
String thirdTimeZone = textReader.readLine();
String[] val = thirdTimeZone.split ("\\s+");
for (int u = 0; u < val.length; u++)
{
int stats = (int)(Math.ceil(Math.abs(Double.parseDouble(val[u]))));
total3 += stats;
data3[u] = stats;
}
total3= total3/180;
atz.setTotal3(total3);
atz.setArray3(data3);
}
}
textReader.close();
return atz;
}
The getArray()
public int[] getArray1 () {
return data1;
}
And setArray()
public void setArray1 (int[] farray) {
int[] data1 = new int[180];
//int[] farray = new int[180];
data1 = farray;
}

The problem seems to be here
public void setArray1 (int[] farray)
{
int[] data1 = new int[180];
//int[] farray = new int[180];
data1 = farray;
}
You're declaring a new variable called data1 and storing the content of farray to it.
After that method is done, that variable will be removed, due to his scope.
Remove int[] from the line int[] data1 = new int[180]; (or just remove the whole line .. it is unnecessary) and your data will be stored in the correct variable that was declared for the class.
public void setArray1 (int[] farray) {
data1 = farray;
}

You have to initialize ArraysTZones

Java Serialization issues

I have this code that writes an object:
FileOutputStream fileOut = new FileOutputStream("Model.ser");
ObjectOutputStream out = new ObjectOutputStream(fileOut);
out.writeObject(this);
out.close();
fileOut.close();
And this code that loads the object:
Model m = null;
try {
FileInputStream fileIn = new FileInputStream("Model.ser");
ObjectInputStream in = new ObjectInputStream(fileIn);
m = (Model) in.readObject();
in.close();
fileIn.close();
} catch (Exception e) {}
setStudentList(m.getStudentList());
setModuleList(m.getModuleList());
I'm pretty sure that saving works, as when I opened the file in notepad++ I saw most of the data that I had saved, but when I load there is no data in module list.
Full source code:
import java.io.*;
import java.util.*;
public class Model implements java.io.Serializable {
private Student[] studentList = new Student[0];
private Module[] moduleList = new Module[0];
public void menu() {
while (true) {
System.out.println ("MENU");
System.out.println ("");
System.out.println (" 1 - Run Tests");
System.out.println (" 2 - Add Student");
System.out.println (" 3 - Add Module");
System.out.println (" 4 - Add Student To Module");
System.out.println (" 5 - Save System (Text file)");
System.out.println (" 6 - Load System (Text file)");
System.out.println (" 7 - Save System (Serialized)");
System.out.println (" 8 - Load System (Serialized)");
System.out.println (" 9 - Print Report");
System.out.println ("");
System.out.print ("Enter choice: ");
String input = keyboard.readString();
switch (input) {
case "1" :
runTests();
break;
case "2" :
System.out.print("First Name : ");
String fN = keyboard.readString();
System.out.print("Surname : ");
String sN = keyboard.readString();
System.out.print("Course Code : ");
String c = keyboard.readString();
System.out.print("User ID : ");
String iD = keyboard.readString();
AddStudent(iD, sN, fN, c);
break;
case "3" :
System.out.print("Module Code : ");
String code = keyboard.readString();
String[] temp = new String[0];
AddModule(code,temp);
break;
case "4" :
System.out.print("Module Code : ");
code = keyboard.readString();
Module m = findAModule(code);
if (m != null) {
System.out.print("User ID : ");
iD = keyboard.readString();
Student s = findAStudent(iD);
if (s != null) {
m.addThisStudent(s);
} else {
System.out.println("Student not found");
}
} else {
System.out.println("Module not found");
}
break;
case "5" :
saveToTextFiles();
break;
case "6" :
loadFromTextFiles();
break;
case "7" :
saveSerialized();
break;
case "8" :
break;
case "9" :
printReport();
break;
}
}
}
public void runTests() {
loadFromTextFiles();
saveSerialized();
printReport();
}
public void loadFromTextFiles() {
studentList = new Student[0];
moduleList = new Module[0];
try {
Scanner fileReader = new Scanner(new InputStreamReader(new FileInputStream("students.txt")));
int num = fileReader.nextInt(); fileReader.nextLine();
for (int i = 0; i < num; i++) {
String u = fileReader.nextLine();
String sn = fileReader.nextLine();
String fn = fileReader.nextLine();
String c = fileReader.nextLine();
AddStudent(u, sn, fn, c);
}
fileReader.close();
fileReader = new Scanner(new InputStreamReader(new FileInputStream("modules.txt")));
num = fileReader.nextInt(); fileReader.nextLine();
for (int i = 0; i < num; i++) {
String code = fileReader.nextLine();
int numOfStudents = fileReader.nextInt(); fileReader.nextLine();
String[] students = new String[numOfStudents];
for (int j = 0; j < numOfStudents; j++) {
students[j] = fileReader.nextLine();
}
AddModule(code, students);
}
fileReader.close();
} catch (IOException e) {}
}
public void saveToTextFiles () {
try {
PrintWriter outfile = new PrintWriter(new OutputStreamWriter (new FileOutputStream("students.txt")));
outfile.println(studentList.length);
for (int i = 0; i < studentList.length; i++) {
outfile.println(studentList[i].getUID());
outfile.println(studentList[i].getSN());
outfile.println(studentList[i].getFN());
outfile.println(studentList[i].getDegree());
}
outfile.close();
outfile = new PrintWriter(new OutputStreamWriter (new FileOutputStream("modules.txt")));
outfile.println(moduleList.length);
for (int i = 0; i < moduleList.length; i++) {
outfile.println(moduleList[i].getCode());
outfile.println(moduleList[i].getStudents().length);
for (int j = 0; j < moduleList[i].getStudents().length; j++) {
outfile.println(moduleList[i].getStudents()[j]);
}
}
outfile.close();
} catch (IOException e) {}
}
public void saveSerialized() {
try {
FileOutputStream fileOut = new FileOutputStream("Model.ser");
ObjectOutputStream out = new ObjectOutputStream(fileOut);
out.writeObject(this);
out.close();
fileOut.close();
FileOutputStream fileOut2 = new FileOutputStream("Module.ser");
ObjectOutputStream out2 = new ObjectOutputStream(fileOut2);
out2.writeObject(studentList);
out2.close();
fileOut2.close();
FileOutputStream fileOut3 = new FileOutputStream("Student.ser");
ObjectOutputStream out3 = new ObjectOutputStream(fileOut3);
out3.writeObject(moduleList);
out3.close();
fileOut3.close();
} catch (IOException e) {}
}
public void loadSerialized() {
Model m = null;
try {
FileInputStream fileIn = new FileInputStream("Model.ser");
ObjectInputStream in = new ObjectInputStream(fileIn);
m = (Model) in.readObject();
in.close();
fileIn.close();
} catch (Exception e) {}
setStudentList(m.getStudentList());
setModuleList(m.getModuleList());
}
private Module[] getModuleList() {
return moduleList;
}
private Student[] getStudentList() {
return studentList;
}
private void setModuleList(Module[] m) {
moduleList = m.clone();
}
private void setStudentList(Student[] s) {
studentList = s.clone();
}
private void AddModule(String code, String[] students) {
int length = moduleList.length;
Module NewArray[] = new Module[length + 1];
for (int i = 0; i < length + 1; i++) {
if (i < length) {
NewArray[i] = new Module(moduleList[i]);
}
}
NewArray[length] = new Module(code, students);
moduleList = NewArray.clone();
}
private void AddStudent(String u, String sn, String fn, String c) {
int length = studentList.length;
Student NewArray[] = new Student[length + 1];
for(int i = 0; i < length + 1; i++) {
if (i < length) {
NewArray[i] = new Student(studentList[i]);
}
}
NewArray[length] = new Student(u, sn, fn, c);
studentList = NewArray.clone();
}
public void printReport() {
for (int i = 0; i < moduleList.length; i++) {
System.out.println(moduleList[i].toString(this));
}
}
public Student findAStudent(String uid) {
for (int i = 0; i < studentList.length; i++) {
if (studentList[i].getUID().compareTo(uid) == 0) {
return studentList[i];
}
}
return null;
}
public Module findAModule(String code) {
for (int i = 0; i < moduleList.length; i++) {
if (moduleList[i].getCode().compareTo(code) == 0) {
return moduleList[i];
}
}
return null;
}
}

Look at your code sample, in particular the switch statement:
switch (input) {
...
case "8" :
break;
...
}
I'd assume the method loadSerialized should be called there but it's missing and is not called anywhere else in the code.
Once you actually call the method that does the loading, the code will work, assuming you have declared a serialVersionUID for both Student and Module.
Edit: why using serialization to persist objects is a bad idea
In simple terms, using serialization to persist objects is brittle.
An object's serialized form is tied to its class. Classes tend to change over time, meaning the serialized instance of the old cannot be loaded into the new.
While you can work round this by setting a serialVersionUID doing so introduces a reverse of the problem where, in the case new fields are introduced, the new cannot be read into objects of the old class, which can be a problem if you do rolling updates to the deployed system.
There's a host of other reasons - it's not easily readable (meaning you can't update it like you would a database or XML/JSON doc), it's inefficient, etc.