CODEWITHSUNDEEP
javagenericsarraylist
tom3322
tom3322

Reputation: 133

Adding generic type objects

I have an array list of generic types and i'm trying to create a method to calculate the average, but I cannot add the a generic without casting it first but I'm suppose to pass in integers or double how can i do this?

private ArrayList<T> grades;

public double computeAverage()
{
    double average = 0;
    double sum = 0;

    for (int i = 0; i < grades.size(); i++) {
        sum = sum + grades.get(i);  <<< ERROR
    }

    average = sum/grades.size();

    return average;

}

Error: The operator + is undefined for the argument type(s) double, T

Upvotes: 1

Views: 89

Answers (1)

qqilihq
qqilihq

Reputation: 11454

Still, after your edit, its unclear what T is. If you're able to narrow it down to a Number (which is the super class for Integer and Double as you mentioned), the following will work:

List<Number> numbers = new ArrayList<Number>();

for (Number number : numbers) {
    sum += number.doubleValue();
}

Upvotes: 8

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