Lambda Expression

Lambda

Functional Interface

• a hint for lambda expression
• ensure only one effectively abstract method

Target Typing

Context for target typing

• method call
• assignment
• constructor

rule for target typing

between the context and the lambda expression (method reference)

• method parameters type should same
• method parameters number should same
• method return type should be compatible
• exception throw by method should be compatible

Lexical scoping

• this refers to enclosing instance (unlike inner class refers to inner class itself)
• any method call refers to enclosing instance method

Method reference

method reference is a effectively lambda expression.

• static method reference
• instance method reference
• instance method reference of an object of particular type
• constructor method reference: Myclass::new
• array constructor method reference: Myclass[]::new

Stream

create stream

intermediate operation & terminal operation

• intermediate operations are always lazy: map, filter
• terminal operations are always eager: forEach sum, max, reduce, collect
• intermediate operations chained with terminal operations forms stream pipeline.