Develop Reference

Keep getting "IndexOutOfBoundsException: Index: 0, Size: 0" when trying to check array entry

I am offering products in the menuItemArrayList and as the user places products of their choice in the shopping cart, they will be added to the selectionItemArrayList. Here is my code that checks to see if the product already exists in the shopping cart. If so then only the quantity gets updated.
I have twiddling around with the code but I keep getting this error
IndexOutOfBoundsException: Index: 0, Size: 0
The code is just an extract from an onClickListener from the recyclerview's onBindHolder:
int position = getAdapterPosition();
for (int j = 0; j <= selectionItemArrayList.size(); j++) {
if (menuItemArrayList.get(position).getMenuItemName().equals(selectionItemArrayList.get(j).selectionName)) { // Loop through selection array to see if item exists in array
selectionItemArrayList.get(j).selectionQuantity += 1; // if it does exist then only update the quantity by 1
} else {
// Get the item name, price and add 1 to the quantity
String menuItemName = menuItemArrayList.get(position).getMenuItemName();
String menuItemPrice = menuItemArrayList.get(position).getMenuItemPrice();
SelectionItem selectionItems = new SelectionItem(menuItemName, menuItemPrice, 1);
selectionItemArrayList.add(selectionItems);
}
}
Any idea what I am doing wrong? The exception is thrown on the line where I compare the product name in the main array with the one in the cart array.

This is your loop:
for (int j = 0; j <= selectionItemArrayList.size(); j++)
When iterating over a list, you almost always want to use <, and not <=. This is because lists indices start from 0. So a list of size 2 has items at 0 and 1.
When you use <= on a list with zero elements, it will still try to access the element at index 0 (because 0 is <= 0). But your list is empty; it has no element at index 0. So you crash.
Try this instead:
for (int j = 0; j < selectionItemArrayList.size(); j++)

Adding a value to string array in android

i am trying enter link description here
as to add values to single as well as 2dim array dynamically,
but while adding values it shows null pointer ,
here is my code
Arr points1[];
points1 = new Arr[listItemList.size()];
for(int i=0;i<listItemList.size();i++)
{
ListItemReminderSummary listItem = listItemList.get(i);
Log.i("listItem.Car_Id", listItem.Car_Type);
points1[i].Car_Id = listItem.Car_Id;
points1[i].Car_Type = listItem.Car_Type;
}
for(int i=0;i<listItemList.size();i++)
{
System.out.println( points1[i].Car_Id + points1[i].Car_Type);
}
Null pointer at points1[i].Car_Id = listItem.Car_Id;
any suggestion,
thnx in advance.

initialize the items in Array...
for (int i = 0; i < listItemList.size(); i++) {
ListItemReminderSummary listItem = listItemList.get(i);
Log.i("listItem.Car_Id", listItem.Car_Type);
points[i] = new Arr();
points1[i].Car_Id = listItem.Car_Id;
points1[i].Car_Type = listItem.Car_Type;
}

You have to initialize cells of array.
for(int i=0;i<listItemList.size();i++){
points[i] = new Arr();
}

You have not Allocated memory to the Arr that is why you're trying to dereference an uninitialised pointer (i.e. writing to a random chunk of memory), which is undefined behaviour.
Change ur starting 2 lines
Arr points1[] = new Arr[listItemList.size()];
for (int i = 0; i < listItemList.size(); i++)
{
ListItemReminderSummary listItem = listItemList.get(i);
Log.i("listItem.Car_Id", listItem.Car_Type);
points1[i].Car_Id = listItem.Car_Id;
points1[i].Car_Type = listItem.Car_Type;
}

Did you make sure that listItemList.get(i) returns a value? Perhaps there is nothing returned from this.

Android shuffle Questions and Answers (string arrays)

I am making an app in which there are list of questions and respective answers.
Questions are in one string array, while answers are in another string array.
I have implemented the following in a wish to shuffle the questions. (Of course the answers need to be linked to that question, else meaningless)
Code:
selected_Q = new String[totalnoofQ];
selected_A = new String[totalnoofQ];
int[] random_code = new int[totalnoofQ];
for (int i = 0; i < totalnoofQ; i++)
{
random_code[i] = i;
}
Collections.shuffle(Arrays.asList(random_code));
for (int j = 0; j < totalnoofQ; j++)
{
int k = random_code[j];
selected_Q [j] = databank_Q [k];
selected_A[j] = databank_A [k];
}
The code reports no fatal error, but the selected_Q is still in sequential order. Why?
Could you please show me how can I amend the codes? Thanks!!!

You shuffle a list created using random_code, but random_code is not modified.
You need to create a temporary list based on random_code. Shuffle this list and then use it to fill the selected_X arrays.
Something like this should work :
int[] random_code = new int[totalnoofQ];
for (int i = 0 ; i < totalnoofQ ; i++) {
random_code[i] = i;
}
List<Integer> random_code_list = new ArrayList<Integer>(); // Create an arraylist (arraylist is used here because it has indexes)
for (int idx = 0 ; idx < random_code.length ; idx++) {
random_code_list.add(random_code[idx]); // Fill it
}
Collections.shuffle(random_code_list); // Shuffle it
for (int j = 0 ; j < totalnoofQ ; j++) {
int k = random_code_list.get(j); // Get the value
selected_Q[j] = databank_Q[k];
selected_A[j] = databank_A[k];
}

Array integer Android

ok so i create an array that has integers. The array displays five number from the min and max. How can i display all five numbers in a textview or edittext ? I tried:
nameofile.setText(al.get(x).toString());
but it only displays one?
ArrayList<Integer> al = new ArrayList<Integer>();
for (int i = minint; i <= maxint; i++)
al.add(i);
Random ran = new Random();
for (int i = 0; i < 5; i++) {
int x = al.remove(ran.nextInt(al.size()));
String myString = TextUtils.join(", ", al);
lottonumbers.setText(myString);

ArrayList<Integer> al = new ArrayList<Integer>();
al.add(0);
al.add(1);
al.add(5);
al.add(4);
al.add(3);
java.util.Collections.sort(al);//for sorting Integer values
String listString = "";
for (int s : al)
{
listString += s + " ";
}
nameofile.setText(listString);

You're currently only printing out one element (the one at index x). If you want to print them all in order, you can just join them using TextUtils.join().
Update: After seeing your edit, I think there's a better way to go about what you're trying to do. Instead of trying to pull the values one at a time, and update the list, why not just shuffle them, then use the above method?
Update 2: Okay, I think I finally understand your problem. Just a simple change, then.
ArrayList<Integer> al = new ArrayList<Integer>();
for (int i = minint; i <= maxint; i++)
al.add(i);
Random ran = new Random();
StringBuilder text = new StringBuilder(); // Create a builder
for (int i = 0; i < 5; i++) {
int x = al.remove(ran.nextInt(al.size()));
if (i > 0)
text.append(", "); // Add a comma if we're not at the start
text.append(x);
}
lottonumbers.setText(text);

al.get(x).toString() will only get the value at index "x". If you want to display all values, you need to combine all of the values from the array into a single string then use setText on that string.

You are only showing one number of your array in the TextView, you must to concat the numbers to see the others results like:
for(Integer integer : al) {
nameofile.setText(nameofile.getText() + " " + al.get(x).toString());
}
Then i think you can show all number in one String.

splitting larger array in to smaller array

In my app I have array size 400 elements. My task is Those elements are send to webservice for inserting.But it is not supported.So split the array into pieces and send to webservice.How is it

Something like this, perhaps?
String[] stringArray = new String[400];
//lets assume that the array has objects in it.
int index = 0;
for(int i = 0; i < stringArray.length; i++) {
String[] temp = new String[20];
for(int x = 0; x < 20) {
if(stringArray[index] != null) temp[x] = stringArray[index];
index++;
}
//The temp array is filled with objects from the other array, so send it to the webservice.
sendArrayToWebService(temp);
}