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Create Global Multidimensional Array dynamically in Java

I have an Ordering System that comprises of a number of steps before the data is finally submitted and stored in the database. I have already completed and implemented the web version of the same Ordering System. Below is the Multidimensional Array in PHP that I created dynamically based on the below values.
In the first step of Order, a Plan is to be selected. Based on that plan, the total number of days will be decided.
Plan 1 - Days Served 26
Plan 1 - Meals Served Per Day 2
Plan 1 - Refreshments Served Per Day 2
Plan 2 - Days Served 5
Plan 2 - Meals Served Per Day 3
Plan 2 - Refreshments Served Per Day 0
and so on...
In the second step, starting date of the Order is to be selected. Weekends are to be excluded and only Weekdays will be counted as days served.
The PHP Multidimensional Array generated dynamically is below
Array
(
[Day 1] => Array
(
[meal_id_1] => Unique ID //to be replaced with user selection
[meal_code_1] => Meal Name //to be replaced with user selection
[meal_type_1] => Meal //prefilled based on the selected package
[meal_id_2] => Not Available //to be replaced with user selection
[meal_code_2] => 2 //to be replaced with user selection
[meal_type_2] => Meal //prefilled based on the selected package
)
[Day 2] => Array
(
[meal_id_1] => Unique ID //to be replaced with user selection
[meal_code_1] => Meal Name //to be replaced with user selection
[meal_type_1] => Meal //prefilled based on the selected package
[meal_id_2] => Not Available //to be replaced with user selection
[meal_code_2] => 2 //to be replaced with user selection
[meal_type_2] => Meal //prefilled based on the selected package
)
In the above code, day number is added dynamically and numeric value in meal_id_1, meal_code_1 and meal_type_1 is also added dynamically.
To connect the App and Web Application logically, I want to post the selection from the App in similar Array.
Since I have Meals and Refreshments to be selected based on the plan, therefore I will be loading Meals for Day 1 and then based on the Plan selected Refreshments for Day 1. There will be 1 Activity for Meals, which be loaded with updated Day number and same for the Refreshments.
Using the below code, I am able to get the Unique ID of the Meals selected in an ArrayList.
int count = 0;
int size = list.size();
List<String> selected_meals = new ArrayList<String>();
for (int i = 0; i<size; i++){
if (list.get(i).isSelected()){
count++;
String selected_meal_string = list.get(i).getMeal_id();
selected_meals.add(selected_meal_string);
}
}
How can I transfer this selection to a Global Multidimensional Array so that in the final step I can post it to be saved in the database?

as per my comment I think you are really looking to use a class here, please see the example below to get you started. You may require some research into how OOP (Object Oriented Programming) works though.
public class Meal {
//I dont know what type of data each attribute is supposed to be so I chose ints. Feel free to change.
private int mealId;
private int mealCode;
private int mealType;
public Meal(int mealId, int mealCode, int mealType){
this.mealId = mealId;
this.mealCode = mealCode;
this.mealType = mealType;
}
public int getMealId() {
return mealId;
}
public int getMealCode() {
return mealCode;
}
public int getMealType() {
return mealType;
}
}
Now the Day class:
import java.util.ArrayList;
public class Day {
private ArrayList<Meal> meals = new ArrayList<>();
public Day(Meal...meals){
//This uses magic params to allow you to pass in as many meals as you want.
for(Meal meal : meals){
this.meals.add(meal);
}
}
public ArrayList<Meal> getMeals() {
return meals;
}
}
Now wherever your main method is:
import java.util.ArrayList;
public class Control {
public static void main(String [] args){
ArrayList<Day> days = new ArrayList<>();
//Create your meals.
Meal meal1 = new Meal(1, 1, 1);
Meal meal2 = new Meal(2, 3, 4);
//Add the meals to a day.
Day day1 = new Day(meal1, meal2);
//Add the day to the list of days.
days.add(day1);
//Getting the meal code for the first meal on the first day. This looks complex, but you would likely break it down before getting values.
System.out.println(days.get(0).getMeals().get(0).getMealCode());
}
}

JFreeChart TimeSeries array exception

this is my first question here ever, and I would appreciate if you can help me.
Since the code I have is way too large to post here, I'll try to describe what my problem is in short.
So, I have made TimeSeries array within my class and array list from where I get values for time series:
private TimeSeries[] seriesArray = new TimeSeries[10];
ArrayList<TempClass> valuesFromArrayList = new ArrayList<>();
I need to make TimeSeries array, because I want to be able to show multiple timeseries graphs. Using only one TimeSeries and addOrUpdate method isn't what I want because then values get mixed when I create more graphs. So, I add values like this:
for(int i = 0; i < valuesFromArrayList.size(); i++)
{
TempClass obj = (TempClass) valuesFromArrayList.get(i);
int timeStamp = obj.getTimeStamp();
int hrsDiff;
int minsDiff;
int secsDiff;
hrsDiff = timeStamp / 3600;
timeStamp = timeStamp - hrsDiff * 3600;
minsDiff = timeStamp / 60;
timeStamp = timeStamp - minsDiff * 60;
secsDiff = timeStamp;
seriesArray[Integer.parseInt(comboBoxValue) - 1].add(new Second(secsDiff, minsDiff, hrsDiff, day, month, year), Math.abs(obj.getValue()));
}
What this part of code does is that it reads values and timestamps from ArrayList I created. There is comboBox where user can choose which timeSeries array index will be in graph. So, if user chooses value 9 from comboBox, timeSeries from index 8 will be chosen and plotted on graph. TimeStamp is simply number of seconds that passed since 00:00:00 at day when values were taken.
TempClass is defined as:
class TempClass
{
private int timeStamp;
private double value;
public TempClass(int a, double b)
{
timeStamp = a;
value = b;
}
public int getTimeStamp()
{
return timeStamp;
}
public double getValue()
{
return value;
}
public void setValue(double val)
{
value = val;
}
}
The problem I have is that when I try to make second (2nd) graph, that is another index of TimeSeries array, I get message:
You are attempting to add an observation for the time period Thu Apr 30 00:00:00 CEST 2015 but the series already contains an observation for that time period. Duplicates are not permitted. Try using the addOrUpdate() method.
I don't want to use addOrUpdate method, I need add method. Values in ArrayList I use to put values into timeSeries are fine, I am 300% sure. I already checked input from comboBox value and it gives correct values.
I have no explanation other that for some reason, even if array index is changed, data I want to write into the series goes to the old series (that is, to the series at the old index). In other words, it seems like even if I change index of array, it keeps writing into the old array index!
It's like equivalent to this (I know this sounds crazy but that is basically what I am getting):
int[] array = new int[5];
array[0] = 1;
array[1] = 2;
System.out.println(array[0]);
And the output I get is
2
This is something I have never heard of before, and I have code similar to this I wrote here in two other places, and in that two places it goes just fine, but in this third place I keep getting that exception.
Is this some kind of bug in JVM?
Does somebody know what this could be?

I don't know too much about TimeSeries, but after skimming the docs about it it says:
"The time series will ensure that (a) all data items have the same
type of period (for example, Day) and (b) that each period appears at
most one time in the series."
Link to Docs
I'm guessing the error is pretty straight forward or a misuse of TimeSeries. It looks like you are simply adding a duplicate date and that the constraints of TimeSeries don't allow that.
You may wish to consider writing a custom class that has the functionality you want. Yet again, I don't know much about TimeSeries, but I hope this helped a little.

Your for loop will always overwrite the value with an index of 0 on seriesArray.
What I mean is, the first time it will write to [0]
The second it will write to [0] then [1]
Is this intended?
I have not looked at the docs too much, but the message says 'the series already contains an observation for that time period.' I think that loop is not doing what you want it to do.

String naming convention in java

I am currently trying to make a naming convention. The idea behind this is parsing.
Lets say I obtain an xml doc. Everything can be used once, but these 2 in the code below can be submitted several times within the xml document. It could be 1, or simply 100.
This states that ItemNumber and ReceiptType will be grabbed for the first element.
ItemNumber1 = eElement.getElementsByTagName("ItemNumber").item(0).getTextContent();
ReceiptType1 = eElement.getElementsByTagName("ReceiptType").item(0).getTextContent();
This one states that it will grab the second submission if they were in their twice.
ItemNumber2 = eElement.getElementsByTagName("ItemNumber").item(1).getTextContent();
ReceiptType2 = eElement.getElementsByTagName("ReceiptType").item(1).getTextContent();
ItemNumber and ReceiptType must both be submitted together. So if there is 30 ItemNumbers, there must be 30 Receipt Types.
However now I would like to set this in an IF statement to create variables.
I was thinking something along the lines of:
int cnt = 2;
if (eElement.getElementsByTagName("ItemNumber").item(cnt).getTextContent();)
**MAKE VARIABLE**
Then make a loop which adds one to count to see if their is a third or 4th. Now here comes the tricky part..I need them set to a generated variable. Example if ItemNumber 2 existed, it would set it to
String ItemNumber2 = eElement.getElementsByTagName("ItemNumber").item(cnt).getTextContent();
I do not wish to make pre-made variable names as I don't want to code a possible 1000 variables if that 1000 were to happen.
KUDOS for anyone who can help or give tips on just small parts of this as in the naming convention etc. Thanks!

You don't know beforehand how many ItemNumbers and ReceiptTypes you'll get ? Maybe consider using two Lists (java.util.List). Here is an example.
boolean finished = ... ; // true if there is no more item to process
List<String> listItemNumbers = new ArrayList<>();
List<String> listReceiptTypes = new ArrayList<>();
int cnt = 0;
while(!finished) {
String itemNumber = eElement.getElementsByTagName("ItemNumber").item(cnt).getTextContent();
String receiptType = eElement.getElementsByTagName("ReceiptType").item(cnt).getTextContent();
listItemNumbers.add(itemNumber);
listReceiptTypes.add(receiptType);
++cnt;
// update 'finished' (to test if there are remaining itemNumbers to process)
}
// use them :
int indexYouNeed = 32; // for example
String itemNumber = listItemNumbers.get(indexYouNeed); // index start from 0
String receiptType = listReceiptTypes.get(indexYouNeed);

Interpreting data strings and inserting it into a JTable in the correct column positions in Java

I'm concerned about my Java client directly connecting to the MySQL server due to all of the issues that could occur, and the security risks I believe it could pose. Such as someone being able to decompile the file and get the login details for the database. As beautiful as it would be, I'm too scared to take that risk. I've written a PHP script to echo data that the client can interpret. The PHP script is what connects to the MySQL.
It's rather simple: Java->PHP->MySQL
I'm going to provide screenshots of the MySQL structure, so you may better understand when trying to visualize this.
id: possibly tid/sid
tid: teacher id, used to link to the teacher
sid: student id, used to link to the student
gid: grade id
aid: assignment id
gp: gained points
pp: possible points
Grading rows are for each assignment per student. So for example if a teacher had 30 students assigned to one assignment, there would be 30 rows in the grading tab and one in the assignments. Duplicate assignment names are NOT allowed.
When the client is requesting the data, I just use a buffered reader & URL to download the string. This is the example output of when the client receives the assignment names.
Test Assignment;Secondary Test Assignment;
This is what it looks like to the client once the column names are downloaded:
As you can see the first two columns are there by default, the last two are assignment names.
I want each row in the table to be a student. However, here is where my trouble comes in. I'm trying to receive the proper data from grading. I don't know how I'm going to do this. I have about 3 months experience with Java, so you could definitely call me a newbie.
Here is my idea, but I didn't think it was so great of an idea:
Search through all of the column names and insert the value into the proper column in that row where assignment name matches.
I didn't know how difficult that would be. I'm guessing the nice people who developed swing built something in for that, but I can't find any resources.
Does anyone have any recommendations on what to do in this situation? I feel lost.

Let's start with the Java client. Here is some code that reads from a php page and that creates a JTable out of it. (actually it's reading from a String for simplicity but you can easily change the code to match your real case, see the comment in the code).
public static void main(String[] args) throws Exception {
String receivedFromPHP = "Student ID;Student Name;Test Assignment;Secondary Test Assignment;\n"
+ "1;Luc;Test assignment 1;Secondary Test assignment 1;\n"
+ "2;Vador;Test assignment 2;Secondary Test assignment 2;";
BufferedReader br = new BufferedReader(new StringReader(receivedFromPHP));
// For real: br = new BufferedReader(new InputStreamReader(new URL("http://localhost/yourPhpPage.php").openStream()));
DefaultTableModel dtm = new DefaultTableModel();
String line;
boolean headersReceived = false;
while ((line = br.readLine()) != null) {
String[] columns = line.split(";");
if (!headersReceived) {
dtm.setColumnIdentifiers(columns);
headersReceived = true;
} else {
dtm.addRow(columns);
}
}
JTable table = new JTable(dtm);
JFrame f = new JFrame();
f.add(new JScrollPane(table));
f.pack();
f.setLocationRelativeTo(null);
f.setVisible(true);
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
Nothing really difficult until now. The real thing is to write the php page with the proper query. Obviously, you know better what you want your page to output but I guess your are going for something like this:
<?php
$mysqli = new mysqli("localhost", "my_user", "my_password", "pinkfluf_dvonx");
/* check connection */
if ($mysqli->connect_errno) {
printf("Connect failed: %s\n", $mysqli->connect_error);
exit();
}
/* Select queries return a resultset */
if ($result = $mysqli->query("SELECT Name FROM City LIMIT 10")) {
printf("Select returned %d rows.\n", $result->num_rows);
/* free result set */
$result->close();
}
/* If we have to retrieve large amount of data we use MYSQLI_USE_RESULT */
if ($result = $mysqli->query('SELECT u.id AS "Student ID", u.username AS "Student Name", ... FROM members u, grading g, assignments a WHERE ...')) {
while($row = $result->fetch_array(MYSQLI_NUM)) {
for ($i=0; $i<sizeof($row); $i++) {
echo $row[$i] . ";";
}
echo "\n";
}
$result->close();
}
$mysqli->close();
?>
Of course, the code I give here is very approximative (given the information I could extract from your question) so it's certain that you'll need to adapt the code to make it work as you'd like to but I hope it can help you getting started (keep going :)).

As far as securing your database, I'd recommend creating a locked down user that can only execute stored procedures - then you don't have to worry about someone decompiling your code. They'd only be able to access what they can access through your code. Here's a tutorial on how to do that.
As far as your main question goes, I would recommend all your data gathering/sorting be done in your SQL query. If you're doing that in the JTable, you end up mixing your Model and View (see MVC for more detail).
So essentailly you want your data coming back from the query in this form:
Student; Student Name; Test Assignment; Secondary Test Assignment
Which means,
You need to add a relation between your grade table and your assignment table (most likely addding aid to the grading table)
You're going to need to come up with a slightly more complicated SQL Query - something like this:
Select g.sid, g.name, a.name from ASSIGNMENTS a
join GRADING g on a.aid = g.aid
where g.tid = 123123 order by g.name
Create a 2D array based on the data and put it in the table (If you're still using your PHP interface, you'll want to split the strings on your delimiters to create a 2D array.)
((DefaultTableModel)table.getModel).setDataVector(data, columnNames);
EDIT
If you're convinced you just want to search through the rows for a value, and then update a column in the row you found - this should get you in the right direction:
Integer searchStudentID = 123123;
int searchColumn = 0;
String updateValue = "Value";
int updateColumn = 3;
//Look through the table for the right row
Vector<Vector<Object>> data = ((DefaultTableModel)table.getModel()).getDataVector();
for(Vector<Object> row : data){
// If on the right row, update it
if(row.elementAt(searchColumn).equals(searchStudentID)){
row.setElementAt(updateValue, updateColumn);
}
}

Tips optimizing Java code

So, I've written a spellchecker in Java and things work as they should. The only problem is that if I use a word where the max allowed distance of edits is too large (like say, 9) then my code runs out of memory. I've profiled my code and dumped the heap into a file, but I don't know how to use it to optimize my code.
Can anyone offer any help? I'm more than willing to put up the file/use any other approach that people might have.
-Edit-
Many people asked for more details in the comments. I figured that other people would find them useful, and they might get buried in the comments. Here they are:
I'm using a Trie to store the words themselves.
In order to improve time efficiency, I don't compute the Levenshtein Distance upfront, but I calculate it as I go. What I mean by this is that I keep only two rows of the LD table in memory. Since a Trie is a prefix tree, it means that every time I recurse down a node, the previous letters of the word (and therefore the distance for those words) remains the same. Therefore, I only calculate the distance with that new letter included, with the previous row remaining unchanged.
The suggestions that I generate are stored in a HashMap. The rows of the LD table are stored in ArrayLists.
Here's the code of the function in the Trie that leads to the problem. Building the Trie is pretty straight forward, and I haven't included the code for the same here.
/*
* #param letter: the letter that is currently being looked at in the trie
* word: the word that we are trying to find matches for
* previousRow: the previous row of the Levenshtein Distance table
* suggestions: all the suggestions for the given word
* maxd: max distance a word can be from th query and still be returned as suggestion
* suggestion: the current suggestion being constructed
*/
public void get(char letter, ArrayList<Character> word, ArrayList<Integer> previousRow, HashSet<String> suggestions, int maxd, String suggestion){
// the new row of the trie that is to be computed.
ArrayList<Integer> currentRow = new ArrayList<Integer>(word.size()+1);
currentRow.add(previousRow.get(0)+1);
int insert = 0;
int delete = 0;
int swap = 0;
int d = 0;
for(int i=1;i<word.size()+1;i++){
delete = currentRow.get(i-1)+1;
insert = previousRow.get(i)+1;
if(word.get(i-1)==letter)
swap = previousRow.get(i-1);
else
swap = previousRow.get(i-1)+1;
d = Math.min(delete, Math.min(insert, swap));
currentRow.add(d);
}
// if this node represents a word and the distance so far is <= maxd, then add this word as a suggestion
if(isWord==true && d<=maxd){
suggestions.add(suggestion);
}
// if any of the entries in the current row are <=maxd, it means we can still find possible solutions.
// recursively search all the branches of the trie
for(int i=0;i<currentRow.size();i++){
if(currentRow.get(i)<=maxd){
for(int j=0;j<26;j++){
if(children[j]!=null){
children[j].get((char)(j+97), word, currentRow, suggestions, maxd, suggestion+String.valueOf((char)(j+97)));
}
}
break;
}
}
}

Here's some code I quickly crafted showing one way to generate the candidates and to then "rank" them.
The trick is: you never "test" a non-valid candidate.
To me your: "I run out of memory when I've got an edit distance of 9" screams "combinatorial explosion".
Of course to dodge a combinatorial explosion you don't do thing like trying to generate yourself all words that are at a distance from '9' from your misspelled work. You start from the misspelled word and generate (quite a lot) of possible candidates, but you refrain from creating too many candidates, for then you'd run into trouble.
(also note that it doesn't make much sense to compute up to a Levenhstein Edit Distance of 9, because technically any word less than 10 letters can be transformed into any other word less than 10 letters in max 9 transformations)
Here's why you simply cannot test all words up to a distance of 9 without either having an OutOfMemory error or simply a program never terminating:
generating all the LED up to 1 for the word "ptmizing", by only adding one letter (from a to z) generates already 9*26 variations (i.e. 324 variations) [there are 9 positions where you can insert one out of 26 letters)
generating all the LED up to 2, by only adding one letter to what we know have generates already 10*26*324 variations (60 840)
generating all the LED up to 3 gives: 17 400 240 variations
And that is only by considering the case where we add one, add two or add three letters (we're not counting deletion, swaps, etc.). And that is on a misspelled word that is only nine characters long. On "real" words, it explodes even faster.
Sure, you could get "smart" and generate this in a way not to have too many dupes etc. but the point stays: it's a combinatorial explosion that explodes fastly.
Anyway... Here's an example. I'm simply passing the dictionary of valid words (containing only four words in this case) to the corresponding method to keep this short.
You'll obviously want to replace the call to the LED with your own LED implementation.
The double-metaphone is just an example: in a real spellchecker words that do "sound alike"
despite further LED should be considered as "more correct" and hence often suggest first. For example "optimizing" and "aupteemising" are quite far from a LED point of view, but using the double-metaphone you should get "optimizing" as one of the first suggestion.
(disclaimer: following was cranked in a few minutes, it doesn't take into account uppercase, non-english words, etc.: it's not a real spell-checker, just an example)
#Test
public void spellCheck() {
final String src = "misspeled";
final Set<String> validWords = new HashSet<String>();
validWords.add("boing");
validWords.add("Yahoo!");
validWords.add("misspelled");
validWords.add("stackoverflow");
final List<String> candidates = findNonSortedCandidates( src, validWords );
final SortedMap<Integer,String> res = computeLevenhsteinEditDistanceForEveryCandidate(candidates, src);
for ( final Map.Entry<Integer,String> entry : res.entrySet() ) {
System.out.println( entry.getValue() + " # LED: " + entry.getKey() );
}
}
private SortedMap<Integer, String> computeLevenhsteinEditDistanceForEveryCandidate(
final List<String> candidates,
final String mispelledWord
) {
final SortedMap<Integer, String> res = new TreeMap<Integer, String>();
for ( final String candidate : candidates ) {
res.put( dynamicProgrammingLED(candidate, mispelledWord), candidate );
}
return res;
}
private int dynamicProgrammingLED( final String candidate, final String misspelledWord ) {
return Levenhstein.getLevenshteinDistance(candidate,misspelledWord);
}
Here you generate all possible candidates using several methods. I've only implemented one such method (and quickly so it may be bogus but that's not the point ; )
private List<String> findNonSortedCandidates( final String src, final Set<String> validWords ) {
final List<String> res = new ArrayList<String>();
res.addAll( allCombinationAddingOneLetter(src, validWords) );
// res.addAll( allCombinationRemovingOneLetter(src) );
// res.addAll( allCombinationInvertingLetters(src) );
return res;
}
private List<String> allCombinationAddingOneLetter( final String src, final Set<String> validWords ) {
final List<String> res = new ArrayList<String>();
for (char c = 'a'; c < 'z'; c++) {
for (int i = 0; i < src.length(); i++) {
final String candidate = src.substring(0, i) + c + src.substring(i, src.length());
if ( validWords.contains(candidate) ) {
res.add(candidate); // only adding candidates we know are valid words
}
}
if ( validWords.contains(src+c) ) {
res.add( src + c );
}
}
return res;
}

One thing you could try is, increase the Java's heap size, in order to overcome "out of memory error".
Following article will help you in order to understand how to increase heap size in Java
http://viralpatel.net/blogs/2009/01/jvm-java-increase-heap-size-setting-heap-size-jvm-heap.html
But I think the better approach to address your problem is, find out a better algorithm than the current algorithm

Well without more Information on the topic there is not much the community could do for you... You can start with the following:
Look at what your Profiler says (after it has run a little while): Does anything pile up? Are there a lot of Objects - this should normally give you a hint on what is wrong with your code.
Publish your saved dump somewhere and link it in your question, so someone else could take a look at it.
Tell us which profiler you are using, then somebody can give you hints on where to look for valuable information.
After you have narrowed down your problem to a specific part of your Code, and you cannot figure out why there are so many objects of $FOO in your memory, post a snippet of the relevant part.