I'm reviewing for an exam. A question on an old test was to: Using an interface, write a method that applies an arbitrary method to every element of an ArrayList. Both the arraylist and method are the parameters to the method.
Would a workable solution be:
public <object> someMethod() {
scanner GLaDOS = new (someArray);
someArray.useDelimiter(",");
for (i = 0; i < someArray.length; i++) {
someOtherMethod(someArray[i]);
}
}
I would've expected something like this:
// define the interface to represent an arbitrary function
interface Function<T> {
void Func(T el);
}
// now the method to apply an arbitrary function to the list
<T> void applyFunctionToArrayList(ArrayList<T> list, Function<T> func){
// iterate over the list
for(T item : list){
// invoke the "arbitrary" function
func.Func(item);
}
}
It's ambiguous in the question, but this might mean returning a new ArrayList, so this might be another acceptable answer
// define the interface to represent an arbitrary function
interface Function<T> {
T Func(T el);
}
// now the method to apply an arbitrary function to the list
<T> ArrayList<T> applyFunctionToArrayList(ArrayList<T> list, Function<T> func){
ArrayList<T> newList = new ArrayList<T>();
// iterate over the list
for(T item : list){
// invoke the "arbitrary" function
newList.add(func.Func(item));
}
}
On a side note, you would then, say, invoke the application like (for example, doubling every number in the list):
ArrayList<Double> list = Arrays.asList(1.0, 2.0, 3.0);
ArrayList<Double> doubledList = applyFunctionToArrayList(list,
new Function<Double>{
Double Func(Double x){
return x * 2;
}
});
