Assignment 6

The indexOf method determines the given element’s location within a collection.

val testVector = Vector("first", "second", "third", "fourth")res11: Vector[String] = Vector(first, second, third, fourth)
testVector.indexOf("second")res12: Int = 1
testVector.indexOf("first")res13: Int = 0

Question 1 1 point

Experiment with indexOf. Which of the following claims correctly describe how the method behaves in case the given element occurs multiple times in the collection?

The method returns a collection containing the index of each occurrence.

The first time you call the method, it returns the first occurrence, then the second, and so forth.

The method always returns the first occurrence (smallest index).

The method always returns the last occurrence (largest index).

The method returns an arbitrary occurrence among the ones found.

The method fails with a run-time error.

Question 2 1 point

And what does indexOf return if there are no occurences of the given element at all?

-1

the length of the collection

an empty collection

nothing; the method fails with a run-time error instead

none of the above

Question 3 4 points

You can also use the parameterless method isEmpty to examine a collection, as well as the contains method, which you can call just like indexOf. Try these methods on some vector or buffer.

Which of the following claims are correct? Select all that apply. Assume that the variable collection refers to some vector or buffer object.

Both isEmpty and contains return a value of type Boolean.

The method call collection.isEmpty produces the same result as the comparison collection.size == 0

The method call collection.contains(someElement) produces the same result as the comparison collection.indexOf(someElement) >= 0

The contains method accepts only parameter values that have the same type as the collection’s elements. For instance, collection.contains(100) fails with an error in case the collection’s elements are strings.

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