Java 8 new features

This article provides a summary of some of the important Java 8 new features.

Java 8 is the newest release of Java and the developer kit is JDK 8.

This is a significant upgrade to Java language.

1.      Introduction of Lambda Expression

Lambda expression is a major change in java as it changes how code is written in java and how solutions are conceptualized.

A lambda expression is a method without a name, access-specifier or return value declaration.

Lambda expression add functional programming features to java. This simplifies and greatly reduces the amount of code written to achieve tasks.

A functional interface is an interface that contains only one abstract method. Then main advantage of it is that it can be used to refer to a lambda expression.

2.      New Stream API

Stream represents a flow of objects on which operations can be performed. Primary aim of streams is to make the operations easy on collections.

The newly added Stream api is available in java.util.Stream package for creating and working with Streams.

It supports pipeline operations on data and is optimized for Lambda expressions.

3.      New java.util.function package

This new package defines number of functional interfaces that provide additional support for lambda expressions.

Predicates and Functions

A predicate is a function with a single argument that returns a boolean value.

Functions are similar to Predicates, but functions return an object as a result.

Both predicates and functions are useful to evaluate lambda expressions.

4.      Interface default methods

Traditionally, interfaces contain only constants and method signatures. They cannot contain method implementations.

Beginning JDK 8, it is possible to define default implementation for a method in an interface. These methods are called default methods.

A default method is declared using a keyword “default” and it contains a method body.

A default method is available to all implementing classes of the interface. If the implementation class wants to use it, it can use it or it can ignore the default implementation and create its own implementation.

5.      New Date Time api

A new Joda Time api was introduced in JDK 8 with the package java.time.

MetaSpace:

With JDK8, the permGen Space has been removed. So where will the metadata information be stored now? This metadata is now stored in a native memory are called as "MetaSpace". This memory is not a contiguous Java Heap memory. It allows for improvements over PermGen space in Garbage collection, auto tuning, concurrent de-allocation of metadata.

Difference between PermGen space and MetaSpace.

PermGen Space	MetaSpace
PermGen always has a fixed maximum size.	Metaspace by default auto increases its size depending on the underlying OS.
Contiguous Java Heap Memory	Native Memory(provided by underlying OS)
Max size can be set using XX:MaxPermSize	Max size can be set using XX:MetaspaceSize
Comparatively ineffiecient Garbage collection. Frequent GC pauses and no concurrent deallocation.	Comparatively effiecient Garbage collection. Deallocate class data concurrently and not during GC pause.