movingMax()

Create a Stream that represents the moving maximum of a Stream<T> looking back windowSize elements.

Implementation Notes

This implementation is suitable for streams whose elements implement Comparable, for a version that takes user-specified Comparator see movingMaxBy(). Nulls are ignored and play no part in calculations.

Signatures

movingMax(int windowSize)

windowSize - How many trailing elements to calculate the maximum value over

Additional Methods

Method	Purpose
`excludePartialValues()`	When calculating the moving maximum values, and the full size of the window has not yet been reached, the gatherer should suppress emitting values until the lookback window is full. See example.
`withOriginal()`	Emit both the original stream element and its calculated moving maximum value wrapped in a `WithOriginal` object. See example.

Examples

Moving maximum over a window size 3

Stream
    .of(3, 2, 1, 3, 4)
    .gather(Gatherers4j.movingMax(3))
    .toList();

// [ 3, 3, 3, 3, 4 ]

Excluding partial values

Showing that in-process moving maximum values are not emitted for each element until the lookback window has been filled.

Stream
    .of(3, 2, 1, 3, 4)
    .gather(Gatherers4j.movingMax(3).excludePartialValues())
    .toList();

// [ 3, 3, 4 ]

Showing nulls are ignored by default

Stream
    .of(null, 3, null, 2, 1, 3, 4)
    .gather(Gatherers4j.movingMax(3))
    .toList();

// [ 3, 3, 3, 3, 4 ]

Emit original value and calculated value

Note that this call may need a type witness due to generic type erasure in Java.

Stream
    .of(3, 2, 1, 3, 4)
    .gather(Gatherers4j.<Integer>movingMax(3).withOriginal())
    .toList();

// [
//   WithOriginal[original=3, calculated=3], 
//   WithOriginal[original=2, calculated=3], 
//   WithOriginal[original=1, calculated=3], 
//   WithOriginal[original=3, calculated=3], 
//   WithOriginal[original=4, calculated=4]
// ]