You have a variable there that keeps track of the sum of the numbers. Using the same pattern, make another variable that keeps track of the largest number seen so far. Initialize it with the value Integer.MIN_VALUE.
@Doleh: where's your explanation? writing copy-me code won't help any one to learn anything. @rayda: either you keep track of the largest number, as Ezzaral suggested, or you store all the given (inputted) numbers into an array. iterate over tjat array and:
if ( arrayNumbers[position] > maxNumber)
maxNumber = arrayNumbers[position];