Functional Interfaces are interfaces with a single method only
Lambda expressions is used primarily to define inline impelementation of functional interfaces
Method references help to point to methods by their names. A method reference is described using ::(double column) symbol. A method reference can be used to point the following types of methods:
static methods
instance methods
constructor using new operator(TreeSet::new)
Functional interfaces has single functionality to exhibit. For example a Comparable interface with a single method compareTo is used for comparison purpose. Java 8 has defined a lot of functional interfaces to be used in lambda expressions in java.util.Function package.
With Java8 default methods can be added to interfaces. If implementing classes doesn’ have these methods, default methods is called.
Streams represents a sequence of objects from a source, which supports aggregate functions. Collection interface has two methods two generate streams:
stream() - returns a sequential stream considering collection as its source.
parallelStream() - returns a parallel stream considering collection as its souce.
