Java-8

Java 8 New Features

There are several new features added in Java 8 version. Some of the important new features are:

1. Define methods inside the interface
2. For each method
3. Lambda Expression
4. Stream API
5. DateTime API

1) Define methods (default, static) inside the Interface

After you published your interface, you can't change it by adding some abstract methods. But if you want to add methods you can define those methods inside the interface. Therefore Java 8 support default and static methods inside the interface.

• In Java 7 version interface only have abstract methods (no method implementation) and an abstract class can have both abstract and non-abstract methods.

• In Java 8 version you can add method implementation in the interface, but you have to declare that method as default method.

ex: default void show(){............}

• To avoid diamond problem you have to override the method in implementation class if two interfaces have same default method

• If class (A) and interface (I) both have the same method an another class (B) use this method that extends A and implements I, B get the method of class A, because class is more powerful than interface

• Static methods are allowed inside the interface. 

2) For each method

If you want to loop collection, until Java 7 you can use for loop or enhanced for loop.

• For loop

• Enhanced for loop

But above two kinds of loops are called external loops. They are fetching the values from outside of the collection.But in Java 8 you can use foreach method to loop and it is considered as an internal loop.

• For each method

For each method implements the accept method in Consumer interface.

3) Lambda Expression

If you have an interface with abstract methods you can use that method implementation in another class without implementing that class with the defined interface. 

4) Stream API 

Stream API contains a lot of methods to handle big data. The methods defined in stream API can be divided into two types

• Intermediate method
• Once you used data you can't use it again
• Terminate method

5) Date/Time API

Date/Time API provides LocalDate, LocalTime and LocalDateTime methods that support to print date and times easily.