Java 8
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This document discusses several new features introduced in Java 8 including lambda expressions, method references, and aggregate operations. Lambda expressions allow implementing functional interfaces using anonymous functions. Method references provide a shorthand way to refer to methods. Aggregate operations involve pipelines and streams that allow processing data in a declarative way by chaining intermediate and terminal operations.
Java 8
- 1. Lambda, Method References & Aggregate Operations Md. Fasihul Kabir Software Engineer, Platform Dhaka, Escenic Asia Ltd.
- 2. Some Cool Features of Java 8 Lambda expressions Method references Default Methods (Defender methods) A new Stream API Optional A new Date/Time API Nashorn, the new JavaScript engine Removal of the Permanent Generation and more…
- 3. Some Cool Features of Java 8 Lambda Expressions Method References Default Methods (Defender methods) A new Stream API Optional A new Date/Time API Nashorn, the new JavaScript engine Removal of the Permanent Generation and more…
- 5. Syntax (arguments) - {body}
- 6. Example button.addActionListener(new ActionListener(){ public void actionPerformed(ActionEvent event){ System.out.println(button clicked); } });
- 7. button.addActionListener(new ActionListener(){ public void actionPerformed(ActionEvent event){ System.out.println(button clicked); } });
- 8. button.addActionListener( event - System.out.println(button clicked) );
- 9. Structure of Lambda Expressions A lambda expression can have zero, one or more parameters The type of the parameters can be explicitly declared or it can be inferred from the context. e.g. (int a) is same as just (a) Parameters are enclosed in parentheses and separated by commas. e.g. (a, b) or (int a, int b) or (String a, int b, float c) Empty parentheses are used to represent an empty set of parameters. e.g. () - 42 When there is a single parameter, if its type is inferred, it is not mandatory to use parentheses e.g. a - return a*a The body of the lambda expressions can contain zero, one or more statements If body of lambda expression has single statement curly brackets are not mandatory and the return type of the anonymous function is the same as that of the body expression When there is more than one statement in body than these must be enclosed in curly brackets (a code block) and the return type of the anonymous function is the same as the type of the value returned within the code block, or void if nothing is returned
- 16. Kinds of Method References Kind Example Reference to a static method ContainingClass::staticMethodName Reference to an instance method of a particular object containingObject::instanceMethodName Reference to an instance method of an arbitrary object of a particular type ContainingType::methodName Reference to a constructor ClassName::new
- 17. Reference to a Static Method The method reference Person::compareByAge is a reference to a static method.
- 18. Reference to an Instance Method of a Particular Object
- 19. Reference to an Instance Method of an Arbitrary Object of a Particular Type
- 20. Reference to a Constructor
- 28. Components of Pipeline A source: This could be a collection, an array, a generator function, or an I/O channel. In this example, the source is the collection roster. Zero or more intermediate operations. An intermediate operation, such as filter, produces a new stream. A terminal operation. A terminal operation, such as forEach, produces a non-stream result, such as a primitive value (like a double value), a collection, or in the case of forEach, no value at all.