Java 8 primer

JAVA 8

Went digging around in Java8 and found a few interesting features which I have tried to explain below:

• Default Methods for Interfaces: Enables us to add non abstract method implementations to interfaces by utilizing default keyword. If a class implements two interfaces which define the same default method, then a compilation error will be thrown.

interface Formula {
	double calculate(int a);

	default double sqrt(int a) {
		return Math.sqrt(a);
	}
}	

• LAMBDAS: Anonymous methods which do not need creation of anonymous classes. - Separation between how to and what to . - returns nothing - Lambdas are not converted to a new function types but to “functional interface” types. - Local variables are accessible but implicitly final. - Fields of class accessible but not implicitly final. - Lambda body(fields etc) scoped by enclosing method as opposed to inner classes.

(Type element) -> { body of function }
e.g: 
	Collections.sort(names, (a, b) -> {
		return b.compareTo(a);
	});

• Method References: Concise method of invoking existing methods.

  • Static references
  • Constructor
  • non-static method
  • non-static method for a specific object

Account::addInterest

• Streams: The name suggests something akin to Input or OutputStream which have existed in Java forever, but Streams are different. They are monads, and bring functional programming in Java

In functional programming, a monad is a structure that represents computations defined as sequence of steps. A type with a monad structure defines what it means
to chain operations, or nest functions of that type together.

- collect is a terminal function to create a collection from stream
- collect(Collector)
- boxed: function to perform autoboxing
- Collector.joining : for concatenating characters