Sorted iteration

Among others, the ObjectUtils provides functions for iterating over sorted collections. There are many use-cases when two collections need to be iterated over, presuming that they are ordered the same way. You can not do this in a simple way, as that requires multiple for loops and temporary collections.

The iterateOrdered and iterateSorted functions can help iterating over two collections/maps:

SortedMap<String, Integer> first;
SortedMap<String, Integer> second;
ObjectUtils.iterateSortedMapEntries(first, second, (key, left, right) -> {
	if (left == null) {
		// first map doesn't contain entry for the key
	} else if (right == null) {
		// second map doesn't contain entry for the key
	} else {
		// both map contain entry for the key
	}
});

The function will iterate both maps the same time, and use their comparators to iterate them in ascending order of their keys. The iteration is O(n + m), where n is the size of the first map, and m is the size of the second. The specified lambda will be called for each present key in both maps.

Using these iteration functions may be significantly faster than performing lookups in a loop. An important use-case that we've found for this is when calculating the deltas for the build tasks in the saker.build system. When large number of files may be present, the sorted iteration is much faster than doing lookups for each file we want to check the changes for.