import net.openhft.chronicle.map.*
.....

interface PostalCodeRange {
    int minCode();
    void minCode(int minCode);

    int maxCode();
    void maxCode(int maxCode);
}

ChronicleMapBuilder<CharSequence, PostalCodeRange> cityPostalCodesMapBuilder =
    ChronicleMapBuilder.of(CharSequence.class, PostalCodeRange.class)
        .averageKey("Amsterdam")
        .entries(50_000);
ChronicleMap<CharSequence, PostalCodeRange> cityPostalCodes =
    cityPostalCodesMapBuilder.create();

// Or shorter form, without builder variable extraction:

ChronicleMap<Integer, PostalCodeRange> cityPostalCodes = ChronicleMap
    .of(CharSequence.class, PostalCodeRange.class)
    .averageKey("Amsterdam")
    .entries(50_000)
    .create();

Map<Long, long[]> socialGraph = ChronicleMap
    .of(Long.class, long[].class)
    .entries(1_000_000_000L)
    .averageValue(new long[150])
    .create();

ChronicleSet<UUID> uuids =
    ChronicleSet.of(UUID.class)
        // All UUIDs take 16 bytes.
        .constantKeySizeBySample(UUID.randomUUID())
        .entries(1_000_000)
        .create();

PostalCodeRange amsterdamCodes = Values.newHeapInstance(PostalCodeRange.class);
amsterdamCodes.minCode(1011);
amsterdamCodes.maxCode(1183);
cityPostalCodes.put("Amsterdam", amsterdamCodes);

...

PostalCodeRange amsterdamCodes = cityPostalCodes.get("Amsterdam");

ChronicleMap<LongValue, Order> orders = ChronicleMap
    .of(LongValue.class, Order.class)
    .entries(1_000_000)
    .create();

LongValue key = Values.newHeapInstance(LongValue.class);
key.setValue(id);
orders.put(key, order);

...

long[] orderIds = ...
// Allocate a single heap instance for inserting all keys from the array.
// This could be a cached or ThreadLocal value as well, eliminating
// allocations altogether.
LongValue key = Values.newHeapInstance(LongValue.class);
for (long id : orderIds) {
    // Reuse the heap instance for each key
    key.setValue(id);
    Order order = orders.get(key);
    // process the order...
}

ChronicleMap<LongValue, CharSequence> names = ...
StringBuilder name = new StringBuilder();
for (long id : ids) {
   key.setValue(id);
   names.getUsing(key, name);
   // process the name...
}

name.setLength(0);
name.append(names.get(key));

ThreadLocal<PostalCodeRange> cachedPostalCodeRange =
   ThreadLocal.withInitial(() -> Values.newHeapInstance(PostalCodeRange.class));

...

PostalCodeRange range = cachedPostalCodeRange.get();
cityPostalCodes.getUsing(city, range);
// process the range...

// a field
PostalCodeRange cachedRange = null;

...

// in a method
cachedRange = cityPostalCodes.getUsing(city, cachedRange);
// process the range...

try (ExternalMapQueryContext<CharSequence, PostalCodeRange, ?> c =
        cityPostalCodes.queryContext("Amsterdam")) {
    MapEntry<CharSequence, PostalCodeRange> entry = c.entry();
    if (entry != null) {
        PostalCodeRange range = entry.value().get();
        // Access the off-heap memory directly, by calling range
        // object getters.
        // This is very rewarding, when the value has a lot of fields
        // and expensive to copy to heap all of them, when you need to access
        // just a few fields.
    } else {
        // city not found..
    }
}

public static boolean addEdge(
        ChronicleMap<Integer, Set<Integer>> graph, int source, int target) {
    if (source == target)
        throw new IllegalArgumentException("loops are forbidden");
    ExternalMapQueryContext<Integer, Set<Integer>, ?> sourceC = graph.queryContext(source);
    ExternalMapQueryContext<Integer, Set<Integer>, ?> targetC = graph.queryContext(target);
    // order for consistent lock acquisition => avoid dead lock
    if (sourceC.segmentIndex() <= targetC.segmentIndex()) {
        return innerAddEdge(source, sourceC, target, targetC);
    } else {
        return innerAddEdge(target, targetC, source, sourceC);
    }
}

private static boolean innerAddEdge(
        int source, ExternalMapQueryContext<Integer, Set<Integer>, ?> sourceContext,
        int target, ExternalMapQueryContext<Integer, Set<Integer>, ?> targetContext) {
    try (ExternalMapQueryContext<Integer, Set<Integer>, ?> sc = sourceContext) {
        try (ExternalMapQueryContext<Integer, Set<Integer>, ?> tc = targetContext) {
            sc.updateLock().lock();
            tc.updateLock().lock();
            MapEntry<Integer, Set<Integer>> sEntry = sc.entry();
            if (sEntry != null) {
                MapEntry<Integer, Set<Integer>> tEntry = tc.entry();
                if (tEntry != null) {
                    return addEdgeBothPresent(sc, sEntry, source, tc, tEntry, target);
                } else {
                    addEdgePresentAbsent(sc, sEntry, source, tc, target);
                    return true;
                }
            } else {
                MapEntry<Integer, Set<Integer>> tEntry = tc.entry();
                if (tEntry != null) {
                    addEdgePresentAbsent(tc, tEntry, target, sc, source);
                } else {
                    addEdgeBothAbsent(sc, source, tc, target);
                }
                return true;
            }
        }
    }
}

private static boolean addEdgeBothPresent(
        MapQueryContext<Integer, Set<Integer>, ?> sc,
        @NotNull MapEntry<Integer, Set<Integer>> sEntry, int source,
        MapQueryContext<Integer, Set<Integer>, ?> tc,
        @NotNull MapEntry<Integer, Set<Integer>> tEntry, int target) {
    Set<Integer> sNeighbours = sEntry.value().get();
    if (sNeighbours.add(target)) {
        Set<Integer> tNeighbours = tEntry.value().get();
        boolean added = tNeighbours.add(source);
        assert added;
        sEntry.doReplaceValue(sc.wrapValueAsData(sNeighbours));
        tEntry.doReplaceValue(tc.wrapValueAsData(tNeighbours));
        return true;
    } else {
        return false;
    }
}

private static void addEdgePresentAbsent(
        MapQueryContext<Integer, Set<Integer>, ?> sc,
        @NotNull MapEntry<Integer, Set<Integer>> sEntry, int source,
        MapQueryContext<Integer, Set<Integer>, ?> tc, int target) {
    Set<Integer> sNeighbours = sEntry.value().get();
    boolean added = sNeighbours.add(target);
    assert added;
    sEntry.doReplaceValue(sc.wrapValueAsData(sNeighbours));

    addEdgeOneSide(tc, source);
}

private static void addEdgeBothAbsent(MapQueryContext<Integer, Set<Integer>, ?> sc, int source,
        MapQueryContext<Integer, Set<Integer>, ?> tc, int target) {
    addEdgeOneSide(sc, target);
    addEdgeOneSide(tc, source);
}

private static void addEdgeOneSide(MapQueryContext<Integer, Set<Integer>, ?> tc, int source) {
    Set<Integer> tNeighbours = new HashSet<>();
    tNeighbours.add(source);
    MapAbsentEntry<Integer, Set<Integer>> tAbsentEntry = tc.absentEntry();
    assert tAbsentEntry != null;
    tAbsentEntry.doInsert(tc.wrapValueAsData(tNeighbours));
}

public static boolean removeEdge(
        ChronicleMap<Integer, Set<Integer>> graph, int source, int target) {
    ExternalMapQueryContext<Integer, Set<Integer>, ?> sourceC = graph.queryContext(source);
    ExternalMapQueryContext<Integer, Set<Integer>, ?> targetC = graph.queryContext(target);
    // order for consistent lock acquisition => avoid dead lock
    if (sourceC.segmentIndex() <= targetC.segmentIndex()) {
        return innerRemoveEdge(source, sourceC, target, targetC);
    } else {
        return innerRemoveEdge(target, targetC, source, sourceC);
    }
}

private static boolean innerRemoveEdge(
        int source, ExternalMapQueryContext<Integer, Set<Integer>, ?> sourceContext,
        int target, ExternalMapQueryContext<Integer, Set<Integer>, ?> targetContext) {
    try (ExternalMapQueryContext<Integer, Set<Integer>, ?> sc = sourceContext) {
        try (ExternalMapQueryContext<Integer, Set<Integer>, ?> tc = targetContext) {
            sc.updateLock().lock();
            MapEntry<Integer, Set<Integer>> sEntry = sc.entry();
            if (sEntry == null)
                return false;
            Set<Integer> sNeighbours = sEntry.value().get();
            if (!sNeighbours.remove(target))
                return false;

            tc.updateLock().lock();
            MapEntry<Integer, Set<Integer>> tEntry = tc.entry();
            if (tEntry == null)
                throw new IllegalStateException("target node should be present in the graph");
            Set<Integer> tNeighbours = tEntry.value().get();
            if (!tNeighbours.remove(source))
                throw new IllegalStateException("the target node have an edge to the source");
            sEntry.doReplaceValue(sc.wrapValueAsData(sNeighbours));
            tEntry.doReplaceValue(tc.wrapValueAsData(tNeighbours));
            return true;
        }
    }
}

HashSet<Integer> averageValue = new HashSet<>();
for (int i = 0; i < AVERAGE_CONNECTIVITY; i++) {
    averageValue.add(i);
}
ChronicleMap<Integer, Set<Integer>> graph = ChronicleMapBuilder
        .of(Integer.class, (Class<Set<Integer>>) (Class) Set.class)
        .entries(100)
        .averageValue(averageValue)
        .create();

addEdge(graph, 1, 2);
removeEdge(graph, 1, 2);

map.close()

class SimpleLoggingMapEntryOperations<K, V> implements MapEntryOperations<K, V, Void> {

    private static final SimpleLoggingMapEntryOperations INSTANCE =
            new SimpleLoggingMapEntryOperations();

    public static <K, V> MapEntryOperations<K, V, Void> simpleLoggingMapEntryOperations() {
        return SimpleLoggingMapEntryOperations.INSTANCE;
    }

    private SimpleLoggingMapEntryOperations() {}

    @Override
    public Void remove(@NotNull MapEntry<K, V> entry) {
        System.out.println("remove " + entry.key() + ": " + entry.value());
        entry.doRemove();
        return null;
    }

    @Override
    public Void replaceValue(@NotNull MapEntry<K, V> entry, Data<V, ?> newValue) {
        System.out.println("replace " + entry.key() + ": " + entry.value() + " -> " + newValue);
        entry.doReplaceValue(newValue);
        return null;
    }

    @Override
    public Void insert(@NotNull MapAbsentEntry<K, V> absentEntry, Data<V, ?> value) {
        System.out.println("insert " + absentEntry.absentKey() + " -> " + value);
        absentEntry.doInsert(value);
        return null;
    }
}

ChronicleMap<IntValue, IntValue> map = ChronicleMap
        .of(Integer.class, IntValue.class)
        .entries(100)
        .entryOperations(simpleLoggingMapEntryOperations())
        .create();

// do anything with the map

enum DualLockSuccess {SUCCESS, FAIL}

class BiMapMethods<K, V> implements MapMethods<K, V, DualLockSuccess> {
    @Override
    public void remove(MapQueryContext<K, V, DualLockSuccess> q, ReturnValue<V> returnValue) {
        while (true) {
            q.updateLock().lock();
            try {
                MapEntry<K, V> entry = q.entry();
                if (entry != null) {
                    returnValue.returnValue(entry.value());
                    if (q.remove(entry) == SUCCESS)
                        return;
                }
            } finally {
                q.readLock().unlock();
            }
        }
    }

    @Override
    public void put(MapQueryContext<K, V, DualLockSuccess> q, Data<V, ?> value,
                    ReturnValue<V> returnValue) {
        while (true) {
            q.updateLock().lock();
            try {
                MapEntry<K, V> entry = q.entry();
                if (entry != null) {
                    throw new IllegalStateException();
                } else {
                    if (q.insert(q.absentEntry(), value) == SUCCESS)
                        return;
                }
            } finally {
                q.readLock().unlock();
            }
        }
    }

    @Override
    public void putIfAbsent(MapQueryContext<K, V, DualLockSuccess> q, Data<V, ?> value,
                            ReturnValue<V> returnValue) {
        while (true) {
            try {
                if (q.readLock().tryLock()) {
                    MapEntry<?, V> entry = q.entry();
                    if (entry != null) {
                        returnValue.returnValue(entry.value());
                        return;
                    }
                    // Key is absent
                    q.readLock().unlock();
                }
                q.updateLock().lock();
                MapEntry<?, V> entry = q.entry();
                if (entry != null) {
                    returnValue.returnValue(entry.value());
                    return;
                }
                // Key is absent
                if (q.insert(q.absentEntry(), value) == SUCCESS)
                    return;
            } finally {
                q.readLock().unlock();
            }
        }
    }

    @Override
    public boolean remove(MapQueryContext<K, V, DualLockSuccess> q, Data<V, ?> value) {
        while (true) {
            q.updateLock().lock();
            MapEntry<K, V> entry = q.entry();
            try {
                if (entry != null && bytesEquivalent(entry.value(), value)) {
                    if (q.remove(entry) == SUCCESS) {
                        return true;
                    } else {
                        //noinspection UnnecessaryContinue
                        continue;
                    }
                } else {
                    return false;
                }
            } finally {
                q.readLock().unlock();
            }
        }
    }

    @Override
    public void acquireUsing(MapQueryContext<K, V, DualLockSuccess> q,
                             ReturnValue<V> returnValue) {
        throw new UnsupportedOperationException();
    }

    @Override
    public void replace(MapQueryContext<K, V, DualLockSuccess> q, Data<V, ?> value,
                        ReturnValue<V> returnValue) {
        throw new UnsupportedOperationException();
    }

    @Override
    public boolean replace(MapQueryContext<K, V, DualLockSuccess> q, Data<V, ?> oldValue,
                           Data<V, ?> newValue) {
        throw new UnsupportedOperationException();
    }

    @Override
    public void compute(MapQueryContext<K, V, DualLockSuccess> q,
                        BiFunction<? super K, ? super V, ? extends V> remappingFunction,
                        ReturnValue<V> returnValue) {
        throw new UnsupportedOperationException();
    }

    @Override
    public void merge(MapQueryContext<K, V, DualLockSuccess> q, Data<V, ?> value,
                      BiFunction<? super V, ? super V, ? extends V> remappingFunction,
                      ReturnValue<V> returnValue) {
        throw new UnsupportedOperationException();
    }
}

class BiMapEntryOperations<K, V> implements MapEntryOperations<K, V, DualLockSuccess> {
    ChronicleMap<V, K> reverse;

    public void setReverse(ChronicleMap<V, K> reverse) {
        this.reverse = reverse;
    }

    @Override
    public DualLockSuccess remove(@NotNull MapEntry<K, V> entry) {
        try (ExternalMapQueryContext<V, K, ?> rq = reverse.queryContext(entry.value())) {
            if (!rq.updateLock().tryLock()) {
                if (entry.context() instanceof MapQueryContext)
                    return FAIL;
                throw new IllegalStateException("Concurrent modifications to reverse map " +
                        "during remove during iteration");
            }
            MapEntry<V, K> reverseEntry = rq.entry();
            if (reverseEntry != null) {
                entry.doRemove();
                reverseEntry.doRemove();
                return SUCCESS;
            } else {
                throw new IllegalStateException(entry.key() + " maps to " + entry.value() +
                        ", but in the reverse map this value is absent");
            }
        }
    }

    @Override
    public DualLockSuccess replaceValue(@NotNull MapEntry<K, V> entry, Data<V, ?> newValue) {
        throw new UnsupportedOperationException();
    }

    @Override
    public DualLockSuccess insert(@NotNull MapAbsentEntry<K, V> absentEntry,
                                  Data<V, ?> value) {
        try (ExternalMapQueryContext<V, K, ?> rq = reverse.queryContext(value)) {
            if (!rq.updateLock().tryLock())
                return FAIL;
            MapAbsentEntry<V, K> reverseAbsentEntry = rq.absentEntry();
            if (reverseAbsentEntry != null) {
                absentEntry.doInsert(value);
                reverseAbsentEntry.doInsert(absentEntry.absentKey());
                return SUCCESS;
            } else {
                Data<K, ?> reverseKey = rq.entry().value();
                if (reverseKey.equals(absentEntry.absentKey())) {
                    // recover
                    absentEntry.doInsert(value);
                    return SUCCESS;
                }
                throw new IllegalArgumentException("Try to associate " +
                        absentEntry.absentKey() + " with " + value + ", but in the reverse " +
                        "map this value already maps to " + reverseKey);
            }
        }
    }
}

BiMapEntryOperations<Integer, CharSequence> biMapOps1 = new BiMapEntryOperations<>();
ChronicleMap<Integer, CharSequence> map1 = ChronicleMapBuilder
        .of(Integer.class, CharSequence.class)
        .entries(100)
        .actualSegments(1)
        .averageValueSize(10)
        .entryOperations(biMapOps1)
        .mapMethods(new BiMapMethods<>())
        .create();

BiMapEntryOperations<CharSequence, Integer> biMapOps2 = new BiMapEntryOperations<>();
ChronicleMap<CharSequence, Integer> map2 = ChronicleMapBuilder
        .of(CharSequence.class, Integer.class)
        .entries(100)
        .actualSegments(1)
        .averageKeySize(10)
        .entryOperations(biMapOps2)
        .mapMethods(new BiMapMethods<>())
        .create();

biMapOps1.setReverse(map2);
biMapOps2.setReverse(map1);

map1.put(1, "1");
System.out.println(map2.get("1"));

    public static <K, V> void printMapStats(ChronicleMap<K, V> map) {
        for (int i = 0; i < map.segments(); i++) {
            try (MapSegmentContext<K, V, ?> c = map.segmentContext(i)) {
                System.out.printf("segment %d contains %d entries\n", i, c.size());
                c.forEachSegmentEntry(e -> System.out.printf("%s, %d bytes -> %s, %d bytes\n",
                        e.key(), e.key().size(), e.value(), e.value().size()));
            }
        }
    }