• Credentials

  • Plugged his book

  • Has a three hour version of the talk.

  • Lambdas

  • Streams

  • Optionals

  • Default methods in interfaces

  • try with resources

  • factory methods

  • Minimize mutability

  • Comparable(14)

  • Live coding

    • Minimize mutability. Value object class. Why? Easier to reason about. Reduces the chance that the system gets into an inconsistent state.

      • Make as many of things final as possible

      • No ctor, use factory method: of. Easier for refactoring. Allows you to change the cardinality, maybe re-use objects with an object pool. Flyweight class. BigDecimal.valueOf() implementation is an example.

      • COMMENT: what about making the zero arg ctor private?

      • He used Google Guava, but noted that they have violated backward compatibility in the past.

      • Advised to implement equals and hashCode. Use the Objects class in the JDK. I thas an equals method. Handles all that null checking. But beware of the performance penalty of autoboxing. For hashcode, there is Objects.hash. This is even worse for performance. If you use the generator for equals and hashcode make sure to keep the impls up to date as the class evolved.

        • for hashcode, because it is immutable, you can do it in the ctor. If you use an object as a key to a hashmap, it must be immutable. If you can’t do that, you can make a toHashKey() method.

      • toString(). It’s for developers. Guava MoreObjects.toStringHelper(). Not for “business strings”. For busness strings, use formatTo with Formatter and Formattable.

      • Comparable. Comparator interface.

    • Functional Interfaces. @FunctionalInterface. Constrains your code to conform to functional interfaces. Favor Strategy over Template Method.

      • You should not need to create a new functional interface. There are 41 already in the JDK. It’s likely it will be in there already. Learn these six well: UnaryOperator, BinaryOperator, Predicate, Function, Supplier, Consumer.

    • Method References. Five different types

      • static, ie Integer::parseInt()

      • bounded and unbounded method reference.

    • Enums

      • Can use lambdas or function references in enum initializer.