public List<Region> findRegionsByKeyRange(final byte[] startKey, final byte[] endKey) {
        final StampedLock stampedLock = this.stampedLock;
        final long stamp = stampedLock.readLock();
        try {
            final byte[] realStartKey = BytesUtil.nullToEmpty(startKey);
            final NavigableMap<byte[], Long> subRegionMap;
            if (endKey == null) {
                subRegionMap = this.rangeTable.tailMap(realStartKey, false);
            } else {
                subRegionMap = this.rangeTable.subMap(realStartKey, false, endKey, true);
            }
            final List<Region> regionList = Lists.newArrayListWithCapacity(subRegionMap.size() + 1);
            final Map.Entry<byte[], Long> headEntry = this.rangeTable.floorEntry(realStartKey);
            if (headEntry == null) {
                reportFail(startKey);
                throw reject(startKey, "fail to find region by startKey");
            }
            regionList.add(safeCopy(this.regionTable.get(headEntry.getValue())));
            for (final Long regionId : subRegionMap.values()) {
                regionList.add(safeCopy(this.regionTable.get(regionId)));
            }
            return regionList;
        } finally {
            stampedLock.unlockRead(stamp);
        }
    }
Returns the list of regions covered by startKey and endKey.
jraft-rheakv/rheakv-core/src/main/java/com/alipay/sofa/jraft/rhea/client/RegionRouteTable.java