Java 8 Handy Notes

Lambda Expression - it helps in implementation of functional interface, lambda expression is treated as a function, so compiler does not create .class file

Java Method References – Method reference is used to refer method of functional interface or class. It is compact and easy form of lambda expression.

There are 3-types of method references in java

1.       Reference to a static method

2.       Reference to a instance method

3.       Reference to a constructor

Syntax for above each type of method references.

1.       Syntax of static Method Reference

<Class name> :: <static method name>

2.       Syntax of instance Method Reference

<Class name> :: <instance method name>

3.       Syntax of Constructor Method Reference

<Class name> :: <new> (it is new keyword)

Functional Interface - any interface that has only one abstract method is called functional interface, @FunctionalInterface annotation can be used to declare an interface as functional interface (optional).

-          It can have any number of static and default methods

-          It should have only one abstract method

-          It is also known as Single Abstract Method Interface (SAM), it is a new feature to achieve functional programming approach

-          A functional interface can extends another interface only when it does not have any abstract method

-          Some of the java pre-defined functional interfaces are

Consumer<T>, Function<T, R>, Predicate<T> ….. Etc.

Streams – Java provides a new additional package in java 8 called java.util.stream, to play or perform any operation on lists, we will convert list into stream and perform operations.

Operations performed on stream are divided into 2-categories

1.       Intermediate operations (e.g., filter, map, sorted ….)

2.       Terminal operations (eg.,  collect, forEach, reduce, …)