Java 8 introduced several new features including lambda expressions, default methods, and the Stream API. It also replaced the PermGen memory space with Metaspace to avoid OutOfMemoryErrors. Some key language updates include support for functional interfaces, lambda expressions, default interface methods, and new collection methods like forEach and filter that work with lambda expressions. The Stream API allows functional-style operations on collections like map, reduce, and filter.

1. JAVA 8

2. OVERVIEW
James Gosling
The father of Java
works in Typesafe Inc. for Scala
Functional Programming

3. LANGUAGE DESIGN
Static and Strongly Typed
Lambda
Stream API
Optional
Method Reference
Default Method
Functional Interface
PermGen is replaced by MetaSpace

4. LIST + LAMBDA
forEach()
(int a, int b) -> {return a + b} (a, b) -> a + b
Iterable has a new default method
Lambda Expression

5. DEFAULT METHOD Interfaces can implement logics…

6. LAMBDA ->

7. BUT… NOT CLOSURE
It should not be a variable but a constant…

8. FUNCTIONAL<T, R>
is implemented by a lambda expression.
has only one method. (except default methods)
Consumer, Supplier, Function, UnaryOperator, Predicate

9. CONSUMER<T>/SUPPLIER<R>

10. PREDICATE<T>
used in filter() to filter a list

11. MAP/REDUCE/FILTER

12. STREAM API
Collection#stream( ).map().map()…

13. PARALLEL
List#parallelStream( )

14. OPTIONAL
Optional.of( your object )
o.ifPresent( do something)

15. METASPACE
PermGen in the heap, classes loaded, are moved into the
OS native memory, Metaspace
Just watch the memory size of the Java process with top
command
No more java.lang.OutOfMemoryError: Perm Gen space
-XX:MetaspaceSize