PushStream

PushStream is an eagerly evaluated, re-usable stream. It continues to push its outputs from one stage to the next until it runs out.

PushStream pushStream = PushStream.fromRange(0, 10);
List<Integer> pushOutput = pushStream.flatMap(x -> PushStream.of(-x * x, x * x)).limit(10).toList();

//Output: [0, 0, -1, 1, -4, 4, -9, 9, -16, 16]

Supported Operations

• Initialization
  • fromList, of, concat, fromRange
• Debugging
  • peek
• Transformation
  • map, flatMap, filter, sorted
  • limit, skip
• Terminal
  • count, fold, sum
  • min, max
  • toList
• See tests file examples

PullStream

PullStream is a lazily evaluated, single-use stream. Each stage only requests for more information from upstream stages if absolutely necessary.

• This makes it possible to work with infinitely large sequences, as long as we use a stage that limits the size of the output (e.g. stream.limit(10)).
• Certain stages like sorted(), sum(), count(), etc. will run forever if you attempt to call it on an infinite stream, since it requires knowing all data before it can return an answer
  • TODO: pass some metadata between stages to hint to the user that they shouldn't try to call such methods, or throw an exception

PullStream counter = PullStream.generator(1, x -> x + 1);
int ans = counter.limit(5).fold(0, (a, b) -> a * 10 + b);
assertEquals(12345, ans);

Supported Operations

• Initialization
  • fromList, fromRange, generator
• Transformation
  • map, flatMap, filter, sorted
  • limit, takeWhile, skip
• Terminal
  • count, fold, reduce
  • min, max
  • toList
• See tests file examples