Advanced Programming in Java
Java 8 New Features
Mehdi Einali
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agenda
Java versions
Default method
Functional interface
Double colon
Functional programing
Lambda expression
Optional
Streams
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Java versions
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Java versions-1
Version
Release Date
1.0
1996
The first stable version
1.1
1997
• an extensive retooling of the AWT event
model
• Inner classes added to language
• Reflection
• I18n and Unicode Support
1.2(j2se)
1998
• Swing Framework
• Collection Framework
1.3
2000
• Java performance engine Hotspot added
• RMI added
2002
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•
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1.4
Main Features
Regular Expression support
Exception Handling high-level api added
Non-Blocking IO(NIO 1) added
Java Web Start
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Java versions-2
Version
1.5(J2SE 5)
Release Date
2004-2009
22 update
2006-2013
1.6(J2SE 6)
More than 50
updates
Last one 113
2011-now
J2SE 7
Many update
Last one 101
Main Features
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•
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Generic Types
Annotation
Autoboxing
Enumorations
Varargs
Foreach
• Performance improvements
• Security Improvements
• JDBC 4
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String in switch
NIO 2
Diamond in generic types
Concurrency high level API
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Java versions-3
Version
Java SE 8
Java SE 9
Java SE 10
Release Date
2014-now
Last update 92
Main Features
• Lambda expression or closure
(Functional Programming)
• JavaScript embedded emulator
• Annotation on Java Type
• default method in interface
• Better support for multi-gigabyte heaps
• Java module system (OSGI like built-in
Scheduled
system)
for March 2017
• Reactive Streams support
• Better support for parallel systems
Scheduled
• Object without Identity
for March 2018 • Support 64-bit addressable arrays
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Default method in
interfaces
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Old interface
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Default keyword
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Default method
In ‘the strictest sense’, Default methods
are a step backwards because they allow
you to ‘pollute’ your interfaces with code
they provide the most elegant way to
allow backwards compatibility
The implementation will be used as default
if a concrete class does not provide
implementation for that method.
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Notes on default
default method can only access
its arguments as interfaces do not have any
state.
Remember interface don’t have object state and its
fields are implicitly public static final
You can write static method in interface and call
it from default method
Both on them don’t depend on method arguments and
class variables rather than object state
All method declarations in an interface, including
static methods, are implicitly public, so you can
omit the public modifier.
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Notes on default
When we extend an interface that contains
a default method, we can perform
following:
Not override the default method and will
inherit the default method.
Override the default method similar to other
methods we override in subclass.
Redeclare default method as abstract, which
force subclass to override it
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Conflicts multiple interface
Since classes in java can implement
multiple interfaces, there could be a
situation where 2 or more interfaces has
a default
method with the same signature hence
causing conflicts as java will not know
what methods to use at a time.
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Functional Programming
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Java programing paradigms
Prior to JavaSE 8, Java supported three
programming paradigms
procedural programming
object-oriented programming
generic programming.
Java SE 8 adds functional programming
programming that treats computation as the
evaluation of mathematical functions and
avoids changing-state and mutable data.
Stateless functions is building block of code
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Why functional programing?
Multi core and multi thread processor increase
every day
Functions can pass as building block of
computations.
Distributes on threads
Collections is every important data structure in
algorithms
In memory storage paradigms are increasing
Collection operations is more frequent process consuming
codes
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collection iteration
External iteration
Developer code do iterations
What you want to accomplish collection oriented task and how
Disadvantages:
Its error prone (keep all intermediate variables consistent)
Duplicate logic
In be optimized in library level
Internal iterations
Just say what you want to accomplish collection oriented task.
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compare
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Functional interface
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Functional interface
An interface that contains exactly one abstract
method (and may also contain default and static
methods).also known as single abstract method
(SAM) interfaces
Functional interfaces are used extensively in
functional programming, because they act as an
object oriented model for a function.
To ensure that your interface meet the
requirements, you should add the optional
@FunctionalInterface annotation.
java.util.function package for basic functional
interfaces
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sample
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Double colon
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Double colon static method
Java 8 enables you to pass references of
methods or constructors via
the :: keyword
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Double colon object method
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Double colon constructor
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Lambda expression
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Lambda expressions
Functional programming is accomplished
with lambda expressions.
A lambda expression represents an
anonymous method—a shorthand notation
for implementing a functional interface,
similar to an anonymous inner class
A lambda consists of a parameter list
followed by the arrow token (->) and a
body
(parameterList) -> {statements}
(int x, int y) -> {return x + y;}
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syntax
When the body contains only one expression, the
return keyword and curly braces may be omitted,
as in:
(x, y) -> x + y
in this case, the expression’s value is implicitly returned
When the parameter list contains
only one parameter, the parentheses may be
omitted, as in
value -> System.out.printf("%d ", value)
() -> System.out.println("Welcome to lambdas!")
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scoping
Accessing outer scope variables from
lambda expressions is very similar to
anonymous objects.
You can access effectively final variables
from the local outer scope as well as
instance fields and static variables.
effectively final means:
Explicitly final
Implicitly final: not explicit final keyword but
acts as final variable
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optional
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optional
Optionals are not functional interfaces, instead
it's a nifty utility to preventNullPointerException.
Optional is a simple container for a value which
may be null or non-null.
Think of a method which may return a non-null
result but sometimes return nothing.Instead of
returning null you return an Optional in Java 8.
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sample
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Streams
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streams
A java.util.Stream represents a sequence of
elements on which one or more operations
can be performed
Stream operations are either intermediate
or terminal.
terminal operations return a result of a certain
type
intermediate operations return the stream itself
so you can chain multiple method calls in a row
Stream operations can either be executed
sequential or parallel.
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sample
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Parallel stream
Streams can be either sequential or
parallel.
Operations on sequential streams are
performed on a single thread while
operations on parallel streams are
performed concurrent on multiple threads.
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sample
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end
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