Effective Java 3/E summary chanpter 3 (Shorter version)

Chanpter 6 : Lambda and Stream

You can find the longer version of this summary here.

• Java 8, Android API 24 or higher

Lambda

• Use Lambda instaed of an anonymous class
• Anonymous class < Lambda < Method reference
  • If the readability seems to be poor, use Lambda instaed of Method reference
• Standard functional interface (java.util.function)
  • 43 in total : 6 basic types can be extended
    • UnaryOperator : 1 argument, argument type = return type
    • BinaryOperator : 2 arguments, argument type = return type
    • Predicate : 1 argument, return booelan
    • Function : 1 argument, argument type != return type
    • Supplier : Returns a value without arguments
    • Consumer : 1 argument, return void
    • Transform 3 pieces each for int, long, and double
    • 9 transformations from Function to SrcToRes
    • transformation that takes 2 arguments (Predicate, Function, Consumer)
    • 2 arguments + return basic type Fuction
    • 1 argument + argument basic type Consumer
    • Supplier that returns Boolean

Stream

• Replace loop (for, while)
• Change the loop to Stream and consider readability
• Cannot be changed to Stream when
  • local variables need to be modified
  • return, break, continue, exception is implemented
• Use java.util.stream.Collectors methods for reducing side-effects
  • toList, toSet, toMap, groupingBy, joining
• Best return type is Collection!
  • Collection can be both (Iterable, Stream).
  • Tremendous sequence can be replaced to AbstractCollecion.
• For parallel(), consider whether (the number of elements * the number of implemented codes > Hundreds of thousands)