java mini talks at qcon

This is part of my live blogging from QCon 2015. See my QCon table of contents for other posts.

This session is four 10 minute talks.

Determininistic testing in a non-deterministic world

  • determinism – everything has a cause and effect
  • pseudorandom – algorihtm that generates approximately random #s

Should see LocalDateTime with Clock instance to reproduce results in a program. There is a fixed clock so all operations in program see the exam exact time. Similar to using a random seed for generating numbers.

Hash spreads and probe functions: a choice of performance and consistency
primitive collections faster/less memory than boxed implementations. Uses 56 bytes for each Integer.

  • hash spread – function that destroys simple patterns in input data while presuming maximal info abobut input. Goal is to avoid collisions without spending too much time hashing.
  • hash probe – function to determining order of slots that span array. For example a linear probe goes down one slot if collision. A quadratic probe goes down down further if collision

Typesafe config on steroids
Property files are hard to scale. Apache Commons adds typing, but still limits to property file format and limit composition. Spring helps with scaling property file.

Typesafe Config – library used by Play and Akaa Standalone project without depenencies so can use in Java. JSON like format called HOCON (human optimized config object notation)

Scopes – library built on top of typesafe config

Real time distributed event driven computing at Credit Suisse
Credit Suisse produced own language that they call “data algebra”. Looks like a DSL.

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