Since you're using Eclipse, all you have to do to format your source code is select-all (CTRL-a), then CTRL-i. Learn to use your tools.
Typically, to find the largest value, the largestValue variable is set to a very small number or the first element of the array. Then, each value in the array is compared to the largestValue:
for ( each element of the arrayItems )
if ( arrayItem[index] > largestValue )
largestValue = arrayItem[index];
What you've done with the arrays sum, highestValue, and lowestValue is either confusing (confused?) or just plain wrong. Those should be single values, not arrays of values.