Method separatorStart

guava/src/com/google/common/base/Splitter.java:144–147

(int start)

        (splitter, toSplit) ->
            new SplittingIterator(splitter, toSplit) {
              @Override
              int separatorStart(int start) {
                return separatorMatcher.indexIn(toSplit, start);
              }

              @Override
              int separatorEnd(int separatorPosition) {