Java 8 Features
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Default methods and static methods allow interfaces to define new methods without breaking existing implementations. The lambda expressions feature introduces functional programming to Java through functional interfaces like Consumer and Function. The streams API provides a functional-style way to process and analyze collections through parallelization, optional return values, and collectors.
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Java 8 Features
- 1. Java 8 Features Lenin Kumar Koppoju
- 2. Agenda • Default Methods • Static Methods • Method Reference Operator • Lambda Expressions (Streams API)
- 3. Default Method • This is a new feature, which allows developer to add new methods to the interface using default keyword without breaking existing implementation. • Object class methods are not allowed as default methods.
- 4. Extending Interfaces that contain default methods • Not mention the default method at all, which lets your extended interface inherit the default method. • Re-declare the default method, which makes it abstract. • Re-define the default method, which overrides it.
- 5. Scenario 1: Implementing multiple Interfaces those contain same name default method • Use the super keyword to invoke a default method in both classes and interfaces.
- 6. Scenario 2: Implementing Interfaces and class, those contain same method • Instance methods are preferred over interface default methods.
- 7. Static Method • This is an extension, which allows developer to add new methods to the interface using static keyword without breaking existing implementation. • Object class methods are not allowed as static methods.
- 8. Static Method • Static Methods are belongs to class. • These methods never override. • Default or general methods never override with Static Methods in sub classes.
- 9. Method Reference Operator • A new powerful operator, added with Java 8. • This operator calls in following ways • Class :: Static_Method • Class :: Method • Instance :: Method
- 10. Method Reference Operator • Keywords super and this can be used with method references.
- 11. Lambda Expressions • A new feature, which allows to write functional programming.
- 12. Lambda Expressions • Functional Interface • This is an Interface with a single abstract method, called the functional method for that functional interface, to which the lambda expression's parameter and return types are matched or adapted. • It provides target types for lambda expressions and method references. • Use @FunctionalInterface annotation to identify/confirm functional interface.
- 13. Lambda Expressions • Functional Interface • These interfaces can provide a target type in multiple contexts, such as assignment context, method invocation, or cast context.
- 14. Lambda Expressions • Base functional interfaces, which are used frequently in lambda’s. • Consumer – consumes one argument, returns nothing • Function – takes one argument, returns one value. • Predicate – checks one argument, returns Boolean (true or false). • Supplier – accepts no argument, returns one value.
- 15. Lambda Expressions • Base functional interfaces, for our notes. • Consumer – process and returns nothing. • Function – used for mapping, process and returns something. • Predicate – used for condition, process and returns true or false. • Supplier – used as a factory, process and returns instance.
- 16. Lambda Expressions • Stream API • This is newly added API in java.util.stream. • This introduces real world functional-style programming into java. • ThisAPI has simplified the collections processing. • You can create streams from collections, arrays, generators, or iterators.
- 17. Lambda Expressions • Stream API • Stream class will create Streams with the help of static methods : contact, empty, generate, iterate, of.
- 18. Lambda Expressions • Streams in parallel • Parallel Stream can be created using Stream.parallel or Collection.parallerStream methods. • This will partition the stream into multiple substreams. • Aggregate operations iterate over and process these substreams in parallel and then combine the results.
- 19. Lambda Expressions • Optional • This a new class added in java.util package to avoid NullPointerException. • A container object which may or may not contain a non-null value. If a value is present, isPresent() will return true and get() will return the value. • Frequently,This class used to be created to return value on safe operations and we can create using static methods : empty, ofNullable, of.
- 20. Lambda Expressions • Comparator • This Provides comparison functionality,Which imposes ordering on collection of objects. • This is a functional interface with compare abstract method. • New static methods are added for convenience to create comparators, multiple value comparing, null values ordering and reverse order.
- 21. Lambda Expressions • Optional • Getting Optional as return on Stream operations : max, min, reduce, findAny, findFirst.
- 22. Lambda Expressions • We can convert the streams to other type using map, mapToXXX (Double, Int, Long) methods. • These conversion streams will be used get statistics like sum, average, max, min, count.
- 23. Lambda Expressions • Stream’s Review
- 24. Lambda Expressions • Optional’s Review
- 25. Lambda Expressions • Collectors – to create collects like list, set and map.
- 29. Thank you… Lenin Kumar Koppoju