Streams - Java 8 Lambdas - page 40

Chapter 2 , even though local variables don't need the final keyword in order to be used in
lambda expressions, they still need to be effectively final .
Whenever you pass lambda expressions into the higher-order functions on the Stream inter-
face, you should seek to avoid side effects. The only exception to this is the forEach meth-
od, which is a terminal operation.
Key Points
▪ Internal iteration is a way of iterating over a collection that delegates more control over
the iteration to the collection.
▪ A Stream is the internal iteration analogue of an Iterator .
▪ Many common operations on collections can be performed by combining methods on
Stream with lambda expressions.
Exercises
NOTE
You can find the answers to these exercises on GitHub .
1. Common Stream operations . Implement the following:
a. A function that adds up numbers, i.e., int addUp(Stream<Integer> num-
bers)
b. A function that takes in artists and returns a list of strings with their names and
places of origin
c. A function that takes in albums and returns a list of albums with at most three
tracks
2. Iteration . Convert this code sample from using external iteration to internal iteration: