Adding consecutive elements of ArrayList

Question

I am trying to achieve the following:

Given a list {146,7,-2,-1} write a new list such that its ith element consists of sums of "i" and i+1".

So this list: {146,153,151,150} would be transformed into 146 as 146+7=153, 153+(-2)=151 and so on. I wrote the following:

List<Integer> list = new ArrayList<Integer>();
List<Integer> list2 = new ArrayList<Integer>();

list2.add(0, list.get(0));

for(int i=0;i<list.size()-1;i++)
{
  list2.add(i+1, list.get(i+1)+list.get(i));
  System.out.println(list2);
}

However, this is returning {146,153,6,-3}. What I am doing wrong?

Denley Bihari · Accepted Answer · 2014-10-10 05:00:17Z

3

You should be adding to list2.get(i) instead of list.get(i)

List<Integer> list = new ArrayList<Integer>();
List<Integer> list2 = new ArrayList<Integer>();
list2.add(0, list.get(0));

for(int i=0;i<list.size()-1;i++)
{
    list2.add(i+1, list.get(i+1)+list2.get(i));
    System.out.println(list2);

}

answered Oct 10, 2014 at 5:00

Denley Bihari

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