Working with an ArrayList of Functions in Java-8

Question

Problem Description: I want to be able to use an ArrayList of Functions passed in from another class (where the Functions have been defined in that other c

Answer 1

The method of a java.util.function.Function object is apply. You need to call it like this:

operations.get(i).apply(initialValue)

However you use raw Function and therefore the result could be Object and you'd need to convert it to the appropriate type. Also you can't use the + (or the +=) operator with it. I'd suggest restricting the parameter types with Number:

List> operations = Arrays.asList(
        num ->  num.intValue() + 1,
        num -> num.intValue() - 1,
        num -> num.doubleValue() * 3.14
        ); // just an example list here 

public double getResult() {
    double result = 0.0;

    for (int i = 0; i < operations.size(); i++) {
        if (i == 0) {
            result = operations.get(i).apply(initialValue).doubleValue();
        } else {
            result += operations.get(i).apply(result).doubleValue();
        }
    }
    return result;
}