Java finding highest in an ArrayList to append

Question

In this segment of code i am searching an Array list with the contents of:

[1,1,2,1,2,1,1,1,1,1,1,1,1,1,1]

I wrote the code to find the indices of the highest values in the ArrayList and then append those indices to a new Arraylist called

int high = findRelevance.get(0);
ArrayList<Integer> IndicesOfHighest = new ArrayList();
for (int iiii = 0; iiii < findRelevance.size(); iiii++)
{
    if (findRelevance.get(iiii) > high)
    {
        IndicesOfHighest.clear();
        IndicesOfHighest.add(iiii);

    }
    if (findRelevance.get(iiii) == high)
    {
        IndicesOfHighest.add(iiii);
    }
}

I would expect to get in return: [ 2, 4 ] but i instead get:

[4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14]

rzwitserloot · Accepted Answer · 2021-01-02 14:35:44Z

1

You are never updating high.
Because there is no else if clause, if you fix that, you'd end up getting [2, 2, 4].

More generally, learn to debug. Programmers don't, as a rule, turn into infallible machines. Use a debugger, or if you don't have the time or the patience to learn how to use one, add a ton of System.out.println statements: The idea is to follow along with the code and calculate, using pen and paper or in your head, what the code should be doing. The moment where you find a discrepancy between what you think should happen and what actually happens? You found a bug, and usually enough context to know what's going wrong.

answered Jan 2, 2021 at 14:35

rzwitserloot

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1 Comment

Bryce Wellman Over a year ago

it has been a long night of coding, thank you very much!!

anurag-dhamala · Accepted Answer · 2021-01-02 14:35:44Z

0

[1,1,2,1,2,1,1,1,1,1,1,1,1,1,1]

int high = findRelevance.get(0);

i.e high = 1. You never updated the value of high. So,

 if (findRelevance.get(iiii) == high)

Due to above line whenever findRelevance.get(iii) == 1 (high is always 1), this if block gets executed.

Thus, you want to update your value of high when its 2.

int high = findRelevance.get(0);
    ArrayList<Integer> IndicesOfHighest = new ArrayList();
    for (int iiii = 0; iiii < findRelevance.size(); iiii++)
    {
        if (findRelevance.get(iiii) > high)
        {
            IndicesOfHighest.clear();
            IndicesOfHighest.add(iiii);
            high = findRelevance.get(iii); //added line


        }
        if (findRelevance.get(iiii) == high)
        {
            IndicesOfHighest.add(iiii);
        }
    }

answered Jan 2, 2021 at 14:35

anurag-dhamala

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1 Comment

Bryce Wellman Over a year ago

it has been a long night of coding, thank you very much!!

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