Napaka pri sortirni metodi?

Lep pozdrav

Imam nalogo predelat sortirno metodo(mergesort), katera je prej delala na tabeli objektov tako da bo zdaj delala na vektorju objektov.
Javlja mi napako

java.lang.ArrayIndexOutOfBoundsException: Array index out of range: 0

pa nevem kaj bi lahko blo narobe...

//NAVADEN MERGE SORT KI DELA S TABELO
public static void mergesort(Element[] a)
{
msort(a,0,a.length);
}

public static void msort(Element[] a, int k, int n)
{

System.out.println("MSort("+k+","+n+")");

if (n>1)
{
msort(a,k,n/2);
msort(a,k+n/2,n-n/2);
merge(a,k,n);

a[0].izpisiTabelo(a);
}
}

public static void merge(Element[] a, int k, int n)
{
System.out.println("Merge("+k+","+n+")");

Element[] temp = new Element[n];
int i=0, lo=k, hi=k+n/2;

while(loMANJSEk+n/2 && hiMANJSEk+n)
temp[i++] = (a[lo].manjsi(a[hi]) ? a[lo++] : a[hi++]);

while(loMANJSEk+n/2)
temp[i++] = a[lo++];

while(hiMANJSEk+n)
temp[i++] = a[hi++];

for(i=0; iMANJSEn; i++)
a[k+i]=temp[i];
}




//MERGE SORT --- SORTIRANJE Z ZLIVANJEM (VEKTOR)
public static void mergesort(Vector|NepOglas| a)
{
msort(a,0,a.size());
}

public static void msort(Vector|NepOglas| a, int k, int n)
{

if (n>1)
{
msort(a,k,n/2);
msort(a,k+n/2,n-n/2);
merge(a,k,n);
}
}

public static void merge(Vector|NepOglas| a, int k, int n)
{

Vector|NepOglas| temp = new Vector|NepOglas|(n);
int i=0, lo=k, hi=k+n/2;

while(loMANJSEk+n/2 && hiMANJSEk+n)
temp.set(i++, (a.get(lo).compareTo(a.get(hi))MANJSE0 ? a.get(lo++) : a.get(hi++)));

while(loMANJSEk+n/2)
temp.set(i++, a.get(lo++));

while(hiMANJSEk+n)
temp.set(i++, a.get(hi++));

for(i=0; iMANJSEn; i++)
a.set(k+i, temp.get(i));
}
}

ve kdo kaj bi blo narobe??

ma ne ni prazen vektor...sam so pa kr neki napake....

sploh mi ni več nč jasno