ensureOrderedBy()

Implementation Notes

This is suitable for streams whose elements do not implement Comparable. For a version that uses the natural order of elements that implement Comparable, see ensureOrdered(). This gatherer is all-or-nothing, meaning it will not emit any intermediate results to its downstream in the event that it detects a failure case.

Signature

ensureOrderedBy(Order order, Comparator<INPUT> coparator)

• order - A non-null Order which elements must be in. Values are Equal, Ascending, Descending, AscendingOrEqual, and DescendingOrEqual
• comparator - A non-null Comparator to compare stream elements

Examples

Ensure that all elements are descending as mapped by the given function - success path

As measured by the length of the input, not its lexicographical order.

Stream
    .of("AAA", "BB", "C")
    .gather(Gatherers4j.ensureOrderedBy(Order.Descending, String::length))
    .toList();

// ["AAA", "BB", "C"]

Ensure that all elements are descending as mapped by the given function - failure path

As measured by the length of the input, not its lexicographical order.

Stream
    .of("AAA", "AA", "AA")
    .gather(Gatherers4j.ensureOrderedBy(Order.Descending, String::length))
    .toList();

// java.lang.IllegalStateException: ensureDecreasingBy detected non-decreasing element