Search:

public static void selection_sort(double []a, String[] str)
{
int i,j;
double max;
int max_index;

for (i=a.length-1;i>0;i--)
{
max = a[0];
max_index = 0;

I can think of a way, to find the largest donation.

double largestAmountDonated = 0;
for (int j = 0; j < amountDonated; j++)
{
if (amountDonated[j] > largestAmountDonated)
{...

Well, have two arrays, if you can.

One stores Strings, the company names.
The other stores values, the amount donated.

String[] companies = new String[5];
double[] amountDonated = new...