1. Major New Language
Features
Neil Brown 10/2014
@neiljbrown neiljbrown.com
2. Overview of Major New Features
● Lambda expressions
● Streams (aka bulk / aggregate data ops)
● Default methods
● Date/time API
● Optional type
3. Lambda Expressions
Anonymous function, with no class
Expression syntax like that of a method
(String s1, String s2) -> s1.length() - s2.length();
Assign to variables or pass as method param
Benefits
● Another means of code reuse
● Terser implementation of single abstract methods (SAMs)
4. Streams API
APIs support aggregating ‘streams’ on-the-fly,
concurrently, using functional methods eg filter
‘Stream’ - seq. of elements from a source
supporting aggregating (‘bulk’) data operations
Concept:
● Convert source to stream
● Process elements in parallel, concurrently
● Collect resulting elements
5. Streams API
Sources include Collections, Array, I/O classes
Benefits
● Better performance via lazy evaluation of
methods on stream and parallel processing
● Replace boilerplate external iteration code eg
List<Student> students = new ArrayList<>(100); ...
List<Student> filteredStudents = students.stream()
.filter(s -> s.getDob().getYear() > yearOfBirthFilter)
.collect(Collectors.toList());
6. Default Methods
Interfaces can include default implementations
interface Logger {
default void info(String message) {
Logger.log("[INFO]", message);
}
...
}
Compiler uses the ‘default method’ in classes
which don’t provide own implementation
7. Default Methods
Interfaces still not permitted to have state
Benefit
● Java APIs can evolve without breaking backwards
compatibility eg add functional methods to Collection
interfaces for Streams
8. Date & Time API
java.time.* -
Addresses issues with java.util.Date and Calendar
● Thread-safe. Immutable classes.
● Consistent design, inspired by Joda-Time
● Better time-zone support
Fluent API; Major classes:
● LocalDateTime and ZonedDateTime - Factory
methods, parsing, truncation
● Period and Duration - lengths of time
9. java.util.Optional
New type for value that may be null
Used as method return type rather than null eg
Optional<Soundcard> optionalSoundcard = computer.getSoundcard();
Forces client to deal with null at compile-time
Provides convenience methods ifPresent(), orElse() for
simpler handling of possible null
Provides null-safe functional methods filter(), map() etc
10. java.util.Optional
Benefits
● More expressive / explicit API methods
● Reduces no. of NullPointerException
● Provided null safe methods reduce need for nested
conditional statements to handle null refs
11. Code Examples
Code examples for each new feature
● https://bitbucket.org/neilbrown - ‘java8-
examples’ repository
Includes pre Java 8 equivalent code to help
identify eligible cases
