runningMaxBy()

Calculate the running maximum value of a Stream<T>, as calculated by the given Comparator.

Implementation Notes

This implementation is suitable for calculating the running maximum value of a Stream<INPUT> via a given Comparator; for a version that operates directly on a Stream<Comparable<INPUT>>, see runningMax(). Nulls are ignored and play no part in calculations.

Signatures

runningMaxBy(Comparator<INPUT> comparator)

comparator - A non-null Comparator<INPUT> to use for comparing elements

Additional Methods

Method	Purpose
`withOriginal()`	Emit both the original stream element and its calculated running maximum value wrapped in a `WithOriginal` object. See example.

Examples

Running maximum value

Stream
    .of("1", "2", "3", "2", "3")
    .gather(Gatherers4j.runningMaxBy(comparing(Integer::valueOf)))
    .toList();

// [ "1", "2", "3", "3", "3" ]

Showing nulls are ignored by default

Stream
    .of(null, "1", null, "2", "3", "2", "3")
    .gather(Gatherers4j.runningMaxBy(comparing(Integer::valueOf)))
    .toList();

// [ "1", "2", "3", "3", "3" ]

Emit original value and calculated value

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

Stream
    .of("1", "2", "3", "2", "3")
    .gather(Gatherers4j.<String>runningMaxBy(comparing(Integer::valueOf)).withOriginal())
    .toList();

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