CompareTo Statement - Null Pointer Exception

I am getting a NullPointerException at my compareTo statement in this section of my code. Why this is popping up?

public static int findPos(String theArray[], String playerName, int arrayCount)
{
int index;
int pos;
for(index = 0; index < arrayCount; index++) {
while ((index < arrayCount) && (playerName.compareTo(theArray[index]) > 0)) {
index++;
}
}
pos = index;
return pos;
}

Error is also creeping up on the line highlighted in a comment as "THIS LINE", and is linked to the compareTo error above.

while(yesOrNo == 'Y' || yesOrNo == 'y')
{
switch(option)
{
//Add a Player and their Stats to the Array

[Code] ....