We Keep Coding

Displaying the string values of 2 dimensional Object array

I am trying to display the contents of an array after iterating through rows and columns of a JTable. I tried Arrays.toString(myTwoDimensionalArrayVariable) but it won't display the string values.
My goal is to check duplicates for every column per row of a destination JTable when user tries to add row values from a source JTable that's why I want to display the contents of the array.
The values on columns are combination of double, String, and int.
int myRowCount = aJTableParameter.getRowCount();
int myColumnCount = aJTableParameter.getColumnCount();
Object[][] myRowValues = new Object[myRowCount][myColumnCount];
for (int j = 0; j < myRowCount; j++) {
for(int i = 0; i< myColumnCount; i++){
myRowValues[j][i] = aDestinationTable.getValueAt(j, i);
}
}
System.out.println(Arrays.toString(myRowValues));
if (Arrays.asList(myRowValues).contains(column1Value)
&& Arrays.asList(myRowValues).contains(column2Value)
&& Arrays.asList(myRowValues).contains(column3Value)
&& Arrays.asList(myRowValues).contains(column4Value)) {
JOptionPane.showMessageDialog(null, "Duplicate, try again.");
}else{
//do something else
}
I only get this output:
run:
Successfully recorded login timestamp
[]
[[Ljava.lang.Object;#35fa3ff2]
[[Ljava.lang.Object;#407c448d, [Ljava.lang.Object;#1e78a60e]
Is there any other alternative than using 2 Dimensional Arrays?
I'd appreciate any help.
Thanks.

IFF your JTable cells contain only Strings, you can define your array as String[][] instead of Object[][] and fill it with your JTable contents using aDestinationTable.getValueAt(j, i).toString().
EDIT: since that's not the case (as per your comment), it's probably better to use a List, like this:
List<List<Object>> objectList = new ArrayList<>();
for (int j = 0; j < 2; j++) {
objectList.add(j, new ArrayList<>());
for (int i = 0; i < 2; i++) {
if (i==0) objectList.get(j).add("string" + j + i);
if (i==1) objectList.get(j).add((double) 37.8346 * j * i);
}
}
System.out.println("OBJECT LIST: "+objectList);
Output:
OBJECT LIST: [[string00, 0.0], [string10, 37.8346]]
Your code should look like this, then:
List<List<Object>> myRowValues = new ArrayList<>();
for (int j = 0; j < myRowCount; j++) {
myRowValues.add(j, new ArrayList<>());
for (int i = 0; i < myColumnCount; i++) {
myRowValues.get(j).add(aDestinationTable.getValueAt(j, i));
}
}
System.out.println(myRowValues);

How to copy elements from `2d array` to `Arraylist`?

folks, what is the technique of copying elements from array to Arraylist?
public DenseBoard(T[][] x, T fillElem){
ArrayList<ArrayList<T>> myBoard = new ArrayList<ArrayList<T>>();
for(int i = 0; i < x.length; i++){
for(int j = 0; j < x[0].length; j++){
myBoard.get(i).add(j); //<<------ getting error!
}
}
}

You'll need to initialize each member of myBoard in the outer loop:
Untested Code Ahead
public DenseBoard(T[][] x, T fillElem){
ArrayList<ArrayList<T>> myBoard = new ArrayList<ArrayList<T>>();
for(int i = 0; i < x.length; i++){
myBoard.add(new ArrayList<T>); //Gotta add something to stick stuff in
for(int j = 0; j < x[0].length; j++){
myBoard.get(i).add(j); //<<------ no more error?
}
}
}
Since myBoard is an ArrayList of ArrayLists of Ts, we need to give it somewhere to put the T's. Initially, myBoard looks like this:
[] <-- empty ArrayList
So we give it somewhere to put data for each row, like this
myBoard.add(new ArrayList<T>);
Now it looks like
[ [] ] <--- ArrayList with an empty ArrayList in it, ready to accept T's
We add some T's, and end up with this
[ [T1, T2, T3] ].
And on the next iteration, we'll end up with something like this
[ [T1, T2, T3], [T4, T5, T6] ]
Hope that cleared things up.

You are getting error because your are trying to get() a value from ArrayList but not had inserted any value first. To do it your way, here is the correct code :
ArrayList<ArrayList<T>> myBoard = new ArrayList<>();
for(int i = 0; i < x.length; i++){
ArrayList<T> values = new ArrayList<>();
for(int j = 0; j < x[0].length; j++){
values.add(x[i][j]);
}
myBoard.add(values);
}
Just use the following function :
Arrays.asList(T...a)
In your case it will be done as :
ArrayList<T> myBoard = new ArrayList<>();
for(T[] arr : x){
myBoard.add(Arrays.asList(arr));
}
Try to use diamond operator <> to make code more readable
Don't reinvent the wheel, use utilities provided at least by core libraries
Make use of for-each statement where you could

Inspired from this post.
new ArrayList<Item>(Arrays.asList(array))
creates a new ArrayList of Item elements from an input array. For two-dimensionals. In this case, you tried this:
public DenseBoard(T[][] x, T fillElem){
ArrayList<ArrayList<T>> myBoard = new ArrayList<ArrayList<T>>();
for(int i = 0; i < x.length; i++){
for(int j = 0; j < x[0].length; j++){
myBoard.get(i).add(j); //<<------ getting error!
}
}
}
The problem is that the line throwing the error assumes you have an ArrayList of ArrayList, but the inner element you try to refer to is not initialized. This should be a fix:
public DenseBoard(T[][] x, T fillElem){
ArrayList<ArrayList<T>> myBoard = new ArrayList<ArrayList<T>>();
for(int i = 0; i < x.length; i++){
myBoard.add(new ArrayList<T>(Arrays.asList(x[i])));
}
//Do something with myBoard
}

Java - Filling multidimensional (2d) ArrayList like a 2d array

A while ago before I got used to object object oriented programming I created a basic TicTacToe game and to create the board I used an array.
The code is a complete mess because I didn't properly understand how to use objects, but I did initialize the board correctly:
char[][] board = new char[3][3];
for (int i = 0; i < board.length; i++){
for (int j = 0; j < board[i].length; j++){
board[i][j] = '[]' //or something like that...don't remember exactly
}
}
My question is how would you this with an ArrayList?
ArrayList <ArrayList<Character>> board = new ArrayList(); // this initialization is not
// wrong using Java 8 but for earlier versions you would need to state the type on both
//sides of the equal sign not just the left
for (int i = 0; i < board.size(); i++){
for (int j = 0; j < board.get(i).size(); j++){
board.get(i).get(j).add('[]');
}
}
but that does not work.
It does not have to be exactly like this, I just generally want to understand how to handle multidimensional ArrayLists.
-thanks

Unlike arrays, you can't initialize an entire ArrayList directly. You can specify the expected size beforehand (this helps performance when you are using very large lists, so it is a good practice to do it always).
int boardSize = 3;
ArrayList<ArrayList<Character>> board = new ArrayList<ArrayList<Character>>(boardSize);
for (int i = 0; i < boardSize; i++) {
board.add(new ArrayList<Character>(boardSize));
for (int j = 0; j < boardSize; j++){
board.get(i).add('0');
}
}

The main difference is that in your original code you had a multi-dimensional array of primitives (in this case, char) and all you had to do was assign a new primitive value to each slot in the array.
However what you want now is an ArrayList of (ArrayList of Character). When you create the ArrayList it is empty. In order to procede you are going to need to fill it with several (ArrayList of Character) before you can begin to start adding Characters themselves.
So for example,
ArrayList <ArrayList<Character>> board = new ArrayList<>();
for (int i=0; i<3; i++) {
board.add(new ArrayList<Character>());
}
Now you can start adding Characters to your lists:
for (int i=0; i<3; i++) {
for (int j=0; j<3; j++) {
board.get(i).add('A');
}
}
Hope this helps.

First you have to initialize the ArrayList in your first line correctly and than you have to initialize an new ArrayList in each run of your first loop:
ArrayList <ArrayList<Character>> board = new ArrayList<ArrayList<Character>>();
for (int i = 0; i < 3; i++){
ArrayList<Character> innerList = new ArrayList<Character>();
board.add(innerList);
for (int j = 0; j < 3; j++){
innerList.add('[');
}
}

Converting from Object[][] to ImageIcon

I am trying to convert my object[][] to an ImageIcon. I current have a public Object[][] images; where I store my images. How do I convert this to an ImageIcon so that I can use it to put it into my JTable? I have tried this:
for(int i = 0; i < 100; i++)
{
...
ImageIcon icon = new ImageIcon(images[i].toString());
// add to table
}
Nothing shows in my table and if I print the value out from the cell this shows: [Ljava.lang.String;#72787a6f
Thanks for any answer.

You have a 2D array so you need to use another index to reference the element at row i column j
for (int i = 0; i < images.length; i++) {
for (int j = 0; j < images[i].length; j++) {
ImageIcon icon = new ImageIcon(images[i][j].toString());
...
}
}
It would make more sense to use a String[][] array

ArrayList of ArrayLists - clear function confusion

Here is a particular method I have written:
class A {
private static ArrayList<ArrayList<Integer>> inputTerms = new ArrayList<ArrayList<Integer>();
public static void method1(ArrayList<Integer> terms) {
ArrayList<Integer> clauses = new ArrayList<Integer>();
int N = terms.size();
for (int i = 0; i < N - 1; i++) {
for (int j = i + 1; j < N; j++) {
clauses.add(-terms.get(i));
clauses.add(-terms.get(j));
inputTerms.add(clauses);
clauses.clear();
}
}
}
}
This method is called multiple times from the main function.
In the end, i try to write the contents of the class variable into a file. However, when I do this, i get 0 as the contents of inputTerms. However, if i remove the clauses.clear() line, i am able to get approppriate values.
My program is such that it is vital for me to clear the clauses after adding to inputTerms. Is there any alternative to this?
**Hmmm.. I have done what you've suggested. However, I haven't quite overcome the problem. To give more background, in my main function, I have the following code:
for (int i=0; i<N-1; i++){
ArrayList<Integer> firstdiagonalTerms = new ArrayList<Integer>();
for (int j=0; j<N-i; j++){
firstdiagonalTerms.add(variable[j][i+j]);
}
method1(firstdiagonalTerms);
}
I have to call the method1 function 4 times for different combinations of 'i' and 'j'. However, I still get 0 when I use the above mentioned suggestions**

You are adding the same list and clearing it repeatedly. When you add an object to a list it copies a reference to it, not a copy of the object.
int N = terms.size();
for (int i = 0; i < N - 1; i++) {
for (int j = i + 1; j < N; j++) {
List<Integer> clauses = new ArrayList<Integer>();
clauses.add(-terms.get(i));
clauses.add(-terms.get(j));
inputTerms.add(clauses);
}
}
or
for (int i = 0, N = terms.size(); i < N - 1; i++)
for (int j = i + 1; j < N; j++)
inputTerms.add(Arrays.asList(-terms.get(i), -terms.get(j)));

Not sure i understand what you are trying to achieve, but you keep reusing the same list, which is probably not what you meant to do.
You should probably move the ArrayList<Integer> clauses = new ArrayList<Integer>(); inside the inner loop, and not call clauses.clear() at all.

When you are adding "clauses" you are adding the actual object to the arrayList, not a copy. So when you clear them all the values in the list will be removed. To get arround this, add a clone of the list:
inputTerms.add((ArrayList<Integer>) clauses.clone());

When you call clear() on list, you are updating/removing same objects (because list contains reference to objects, not copy of object). That is what causing the issue.
I think you need to do something like below. Instead of using clear(), create a new list everytime.
public static void method1 (ArrayList<Integer> terms)
{
int N = terms.size();
for (int i = 0; i<N-1; i++) {
for (int j=i+1; j<N; j++) {
ArrayList<Integer> clauses = new ArrayList<Integer>();
clauses.add(-terms.get(i));
clauses.add(-terms.get(j));
inputTerms.add(clauses);
}
}