CODEWITHSUNDEEP
javaarraysloops
Ned
Ned

Reputation: 23

ArrayList element Counting

I ArrayLists, the data includes months of the year 2015, 2016 and 2017.

Data is grouped as - For Year 2015, months are from 05 to 12 - For 2016, months are from 01 to 12 and - For 2017, month 01 to 06 - Months are in sequence as:

 [05, 05, 05, 06, 06, 06, 06, 06, 06, 06, 06, 06, 06, 06, 06, 06, 06, 06, 06, 06, 06, 06, 06, 06, 06, 06, 06, 06, 07, 07, 08, 08, 08, 08, 08, 08, 08, 08, 08, 08, 08, 08, 08, 08, 08, 09, 09, 09, 09, 09, 09, 09, 09, 09, 09, 09, 09, 09, 09, 09, 09, 09, 09, 09, 09, 09, 09, 09, 09, 09, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 01, 01, 01, 01, 01, 01, 01, 01, 01, 01, 01, 01, 01, 01, 01, 01, 01, 01, 01, 01, 01, 02, 02, 02, 02, 02, 02, 02, 02, 02, 02, 02, 02, 02, 02, 02, 02, 02, 02, 02, 02, 02, 03, 03, 03, 03, 03, 03, 03, 03, 03, 03, 03, 03, 03, 03, 03, 03, 03, 03, 03, 03, 03, 03, 03, 03, 03, 04, 04, 04, 04, 04, 04, 04, 04, 04, 04, 04, 04, 04, 04, 04, 04, 04, 04, 04, 04, 04, 04, 04, 04, 04, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 06, 06, 06, 06, 06, 06, 06, 06, 06, 06, 06, 06, 06, 06, 06, 07, 08, 08, 08, 08, 08, 08, 08, 08, 08, 08, 08, 08, 08, 08, 08, 08, 08, 08, 08, 08, 08, 08, 08, 08, 08, 09, 09, 09, 09, 09, 09, 09, 09, 09, 09, 09, 09, 09, 09, 09, 09, 09, 09, 09, 09, 09, 09, 09, 09, 09, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 01, 01, 01, 01, 01, 01, 01, 01, 01, 01, 01, 01, 01, 01, 01, 01, 01, 01, 01, 01, 01, 02, 02, 02, 02, 02, 02, 02, 02, 02, 02, 02, 02, 02, 02, 02, 02, 02, 02, 02, 02, 02, 03, 03, 03, 03, 03, 03, 03, 03, 03, 03, 03, 03, 03, 03, 03, 03, 03, 03, 03, 03, 03, 03, 03, 03, 03, 04, 04, 04, 04, 04, 04, 04, 04, 04, 04, 04, 04, 04, 04, 04, 04, 04, 04, 04, 04, 04, 04, 04, 04, 04, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05, 05]

What I am trying to do is: counting the number of months is repeated in the consecutive cell in the array. For example 05 month is repeated 3 times and month 6 is repeated 25 times and so on. But it gives me the following error:

java.lang.IndexOutOfBoundsException: Index: 534, Size: 534
Execution Completed
    at java.util.ArrayList.rangeCheck(Unknown Source)
    at java.util.ArrayList.get(Unknown Source)
    at yearandmonth.task(yearandmonth.java:84)

And here is my Approach

int counter = 1;
                    ArrayList<Integer> monthCounterArray = new ArrayList<Integer>();
                    for(int mn = 0; mn <= monitoringMonthArray.size(); mn++){
                        if(monitoringMonthArray.get(mn).equals(monitoringMonthArray.get(mn + 1))){
                            counter++;
                        }
                        else {
                            System.out.println("Month " + monitoringMonthArray.get(mn)+ " Repeated " + counter);
                            monthCounterArray.add(counter);
                            counter = 1;
                        }
                    }

BTW monitoningMonthArray size is 534 in my case

Hope I have provided enough information

Thanks in advance

Upvotes: 0

Views: 91

Answers (4)

anvita surapaneni
anvita surapaneni

Reputation: 369

(int mn = 0; mn <= monitoringMonthArray.size(); mn++) this will iterate size + 1 times.

(int mn = 0; mn < monitoringMonthArray.size(); mn++)

iterates size times,

but since you are accessing mn +1 th item , you should loop for size -1 times.

(int mn = 0; mn < monitoringMonthArray.size()-1; mn++)

this should work.

Upvotes: 0

Sergei Sirik
Sergei Sirik

Reputation: 1289

Here is the solution if I get your question right:

public static void main(String[] args) {
    List<String> monthCounterArray = Arrays.asList(new String[] { "05", "05", "05", "06", "06", "06", "06", "06", "06", "06", "06", 
        ... <your array> 
    "05", "05" });

    List<String> monthCounterArray_1 = Arrays.asList(new String[]{ "05", "05", "05", "06", "06", "06", "07", "07", "08", "09", "09", "10", "10",
            "11", "12", "12", "12", "01", "01", "01", "01", "01", "02", "03", "04", "04", "04", "04", "04", "05",
            "05", "05", "05", "06", "07", "08", "09", "10", "11", "12", "01", "01", "01", "01", "01"});

    List<String> monthCounterArray_2 = Arrays.asList(new String[] {});

    List<Integer> output = countOccurences(monthCounterArray);
    List<Integer> output_1 = countOccurences(monthCounterArray_1);
    List<Integer> output_2 = countOccurences(monthCounterArray_2);

    System.out.println(Arrays.toString(output.toArray()));
    System.out.println(Arrays.toString(output_1.toArray()));
    System.out.println(Arrays.toString(output_2.toArray()));
}

private static List<Integer> countOccurences(List<String> input) {
    List<Integer> output = new ArrayList<>();
    String previousValue = "-1";
    int k = 0;

    for (String fromInput : input) {
        if (previousValue.equals("-1")) {
            output.add(k, 1);
            previousValue = fromInput;
        } else if (previousValue.equalsIgnoreCase(fromInput)) {
            output.set(k, output.get(k) + 1);
        } else {
            if (k != 0) {
                output.set(k, output.get(k) + 1);
            }
            previousValue = "-1";
            k++;
        }
    }
    return output;
}

And output:

[3, 25, 2, 15, 25, 25, 25, 25, 21, 21, 25, 25, 25, 15, 26, 25, 25, 25, 25, 21, 21, 25, 25, 24]
[3, 3, 2, 3, 2, 4, 5, 2, 5, 4, 2, 2, 2, 5]
[]

Upvotes: 0

ByeBye
ByeBye

Reputation: 6946

In your for loop check mn <= monitoringMonthArray.size() you are have situation where mn is equal to size of your list. List (and arrays) in java are indexed from 0 to size - 1.

So, if you have list with size==1, calling get(1) is trying to get second element.

Another thing is that monitoringMonthArray.get(mn + 1) can exceed your size either.

You condition should be:

for(int mn = 0; mn < monitoringMonthArray.size() - 1; mn++)

Upvotes: 2

davidxxx
davidxxx

Reputation: 131356

This condition makes no sense :

 for(int mn = 0; mn <= monitoringMonthArray.size(); mn++){

as monitoringMonthArray is an ArrayList and get(int) with as parameter the size of the List is out of the bound of the ArrayList.

So as in the loop you write :

monitoringMonthArray.get(mn)

you will necessarily finish with a IndexOutOfBoundsException that is thrown.

Besides, this condition in the loop body:

if(monitoringMonthArray.get(mn).equals(monitoringMonthArray.get(mn + 1))){

requires you iterate at most until the last-1 element for the same reason :

So the loop condition should be :

 for(int mn = 0; mn < monitoringMonthArray.size()-1; mn++){

Upvotes: 0

Related Questions