Moving elements in an array

Question

I have an array of objects and i want to add elements in this array and simultaneously sort them in ascending order.Although I tried many compinations , I always take a java.lang.ArrayIndexOutOfBoundsException. Here is a part of my code :

public boolean insert(Person p)
{
    for(int i=0;i<=size();i++)
    {   
        if (c==0)
        {   
            array[0] = p;
            c++;
            return true;
        }
        else
        {   
            if (p.compareTo(array[i])==-1)
            {
                array[i]=p;
                c++;
                for(int j = size(); j>i; j--)
                {
                    array[j]=array[j-1];
                }
            }
            else if((p.compareTo(array[i])==1))
            {
                array[i+1]=p;
                c++;
                for (int j=(size()-1);j>= i+1; j--)
                {
                    array[j+1]=array[j];
                }
            }
            else
            {
                return false;
            }
            return true;
        }
    }
    return false;
}

private int c;
private Person array[];
public SortedPersonList()
{   
    this.array = new Person[c];
}
public int size()
    {
        return c;
    }

Use a TreeSet<Person>. It will do that for you, and do it much faster. — JB Nizet
– JB Nizet, Commented Apr 13, 2014 at 13:05
if size() == array.length, than you are accessing array[array.length], which is illegal. — Eyal Schneider
– Eyal Schneider, Commented Apr 13, 2014 at 13:08
Library solutions - best solutions! Specially for more or less common things. Though using a TreeSet is slightly misguided, since the data structure at hand is an array and allows multiple equal objects — Ordous
– Ordous, Commented Apr 13, 2014 at 13:09
@DiVeRsi0n: And how do you initialize the array? It probably needs to be resized, otherwise the capacity is bounded. — Eyal Schneider
– Eyal Schneider, Commented Apr 13, 2014 at 13:11

HelloWorld123456789 · Accepted Answer · 2014-04-13 13:05:49Z

1

Remove the equal sign in for(int i=0;i<=size();i++). That is, change to

for(int i=0;i<size();i++)

Array indices go from 0 to size-1. So array[size()] is outside the array. Hence the error.

answered Apr 13, 2014 at 13:05

HelloWorld123456789

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Eyal Schneider · Accepted Answer · 2014-04-13 13:48:26Z

0

1) You are initializing your array to a size 0, and you never resize it. An array has a fixed size, so in order to populate it with items beyond its range, you should first create a larger array and copy the contents to it (This is how ArrayList works).

2) When you find the insertion point, you shouldn't override this position before keeping its value in a temp variable. (Also, I don't understand the third case in your code. Why do you insert if p is greater than array[i]? you should rethink your logic.)

3) you may want to use binary search to find the insertion point. It has a better performance than linear search.

edited Apr 13, 2014 at 13:48

answered Apr 13, 2014 at 13:33

Eyal Schneider

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1 Comment

DiVeRsi0n Over a year ago

I must insert every time the main method calls the insert(), apart from the case that already a same object already exists in the array.

Benjamin · Accepted Answer · 2014-04-13 13:08:16Z

0

Your code :

    for(int i=0;i<=size();i++)

Write like

    for(int i=0;i<size();i++)  or  for(int i=0;i<=size()-1;i++)

answered Apr 13, 2014 at 13:08

Benjamin

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