Lambda Expression

• Since first java version(1.0) many new features were added but later in JDK5 added fundamentally changing the way that code is written.
• In these JDK8 lambda expression is introduced due to 2 reasons.
• First is add the new syntax that increase the expressive power of the language where constructs are followed in certain order.
• Second, the new capabilities were introduced into the API library.
• In final analysis the generics reshaped java several years ago and now lambda expressions reshaped the java today.
• And over few years the lambda expressions are developed in C# and C++.

Introducing Lambda Expressions:

• It is used to implement a method defined by a functional interface.It is form of anonymous class .

• lambda expressions is also referred as closures.

• Functional interface contains one and only abstract method.It represent a single action.

• A functional interface refers to SAM type(Single Abstract Method)

Lambda expressions fundamentals:

• The new syntax element is used in java language is introduced.
• The left side specifies the any parameter required by lambda expressions.

• The right side specifies the lambda body which shows the actions of lambda expressions.

• It define two types of lambda bodies;

• First as single expressions and second as block of code

• And these first types as single expression as,

                                              () -> 123.45
  

• This lambda expression takes no parameters, thus the parameter list is empty.

• It returns the constant value 123.45.

• Therefore the method,

                                     double myMeth() { return 123.45; }
  

• When a lambda expression requires a parameter, it is specified in the parameter list on
  the left side of the lambda operator,

                                             (n) -> (n % 2)==0
  

• These lambda expressions returns true only if the parameter of n is even.