c_4_7_summary

🧠 4.7 Summary

• Lambdas can references static and instance variables from wihtin. They can also access local variables which are effectively final - meaning the variable has not been reassigned or is literally labeled final!

• I must know the following functional interfaces!:

1. Supplier<T>: get() returns T
2. Consumer<T>: `accept(T t) returns void
3. BiConsumer<T, U>: `accept(T t, U u) returns void
4. Predicate<T>: test(T t) returns booolean
5. BiPredicate<T, U>: test(T t, U u) returns boolean
6. Function<T, R>: apply(T t) returns R
7. BiFunction<T, U, R>: apply(T t, U u) returns R
8. UnaryOperator<T>: apply(T t) returns T
9. BinaryOperator<T>: apply(T t1, T t2) returns T

• An Optional can be used to store a value or its empty. We can can use ifPresent() and get() to get its value.

• We have 3 methods for Optionals which accept functional interfaces:

1. ifPresent(Consumer c)
2. elseGet(Supplier s)
3. orElseThrow(Supplier c)

• Stream pipelines have 3 parts:

1. Source of data

2. Intermediate Operations - optional and can be multiple. E.g. filter(), flatMap(), sorted()

3. Terminal Operation - e.g. allMatch(), count(), forEach()

• We can create streams for primitive data types, for these we must use DoubleStream, IntStream and LongStream!

• We can quickly generate a stream of INTEGERS within a range using range(i,j) and rangeClosed(i,j). These methods are only available on DoubleStream and IntStream!

• We have access to average(), min(), max() for these primitive streams. We can also generate a SummaryStatistic by calling summaryStatistics()

• We have functional interfaces specifically for boolean, e.g. BooleanSupplier can be use to generate a primitive boolean value!