max non negative subarray using arraylist

Question

i am trying to solve this question using arraylist in java but there is some error. can you tell me what is it that m doing wrong ? I'm using eclipse indigo and its showing the following error:

Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
  at java.util.ArrayList.rangeCheck(Unknown Source)
  at java.util.ArrayList.get(Unknown Source)
  at hackerrank.maxsub(hackerrank.java:32)
  at hackerrank.main(hackerrank.java:16)

private static ArrayList<Integer> maxsub(int[] input) {
    ArrayList<ArrayList<Integer>> temp=new ArrayList<ArrayList<Integer>>();
    int j=0;
    Integer[] sumarray=new Integer[temp.size()];
    for(int i=0;i<input.length;i++)
    {

        if(input[i]>=0)
        {
            temp.get(j).add(input[i]);
            sumarray[j]=sumarray[j]+input[i];
        }
        else
        {
            j++;
        }

    }
    int maxsum=Integer.MIN_VALUE;
    int indexofmaxsum=-1;
    for(int a=0;a<sumarray.length;a++)
    {
        if(sumarray[a]>maxsum)
        {
            maxsum=sumarray[a];
            a=indexofmaxsum;
        }
    }

    return temp.get(indexofmaxsum);
}

here temp is holding a arraylist type element and sadly it is empty — bananas
– bananas, Commented Jun 14, 2016 at 3:45
It looks like temp is never populated, which means any call to temp.get() will throw an error. — castletheperson
– castletheperson, Commented Jun 14, 2016 at 3:45
please read this (javatpoint.com/ArrayList-in-collection-framework) for some basics — bananas
– bananas, Commented Jun 14, 2016 at 3:47

user2150837 · Accepted Answer · 2016-06-14 03:57:19Z

2

Your problem lies in below statement:

temp.get(j).add(input[i]);

You have created an Arraylist of ArrayList(containing Integers),

ArrayList<ArrayList<Integer>> temp=new ArrayList<ArrayList<Integer>>();

and you haven't added any element(ArrayList of Integers in this case) and trying to get an element using temp.get(j).add(input[i]);

You'll also experience problem here

  Integer[] sumarray=new Integer[temp.size()];

as you have instantiated an array of size 0(as temp is empty). And

  sumarray[j]=sumarray[j]+input[i];

this will also cause same exception

answered Jun 14, 2016 at 3:57

user2150837

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2 Comments

Neha Over a year ago

then how do i add the value of input[i] to my arraylist of arraylist ?

user2150837 Over a year ago

Now you know, where the problem is. Try to figure out a way. But before that you need to get basics right. Follow a beginner's book and attempt standard algorithms first.

Zay Ya · Accepted Answer · 2016-06-14 03:57:00Z

0

You should be aware temp.size is zero before assign to sumarray

Integer[] sumarray=new Integer[temp.size()];

answered Jun 14, 2016 at 3:57

Zay Ya

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Comments

siko24s · Accepted Answer · 2016-06-14 05:55:05Z

0

Copy part of your code

ArrayList<ArrayList<Integer>> temp=new ArrayList<ArrayList<Integer>>();
    int j=0;
    Integer[] sumarray=new Integer[temp.size()];
    for(int i=0;i<input.length;i++)
    {

        if(input[i]>=0)
        {
            temp.get(j).add(input[i]);
            sumarray[j]=sumarray[j]+input[i];
        }
        else
        {
            j++;
        }

    }

temp seems not populated before used so calling get(0) must throws null exception.
Inner ArrayList instance did not initialized. Call add() function will also produce a null pointer exception alert.

Hope this helps you.

answered Jun 14, 2016 at 5:55

siko24s

1

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