A small toolkit of classes that support lock-free thread-safe programming on single records. In essence, the classes here provide provide an atomic conditional update operation of the form:

 boolean compareAndSet(expectedValue, updateValue); 

This method (which varies in argument types across different classes) atomically sets a record to the updateValue if it currently holds the expectedValue, reporting true on success. Classes jere also contain methods to get and unconditionally set values.

The specifications of these methods enable to employ more efficient internal DB locking. CompareAndSwap operation is typically faster than using transactions, global lock or other concurrent protection.

Instances of classes Atomic.Boolean, Atomic.Integer, Atomic.Long, Atomic.String and Atomic.Var each provide access and updates to a single record of the corresponding type. Each class also provides appropriate utility methods for that type. For example, classes Atomic.Long and Atomic.Integer provide atomic increment methods. One application is to generate unique keys for Maps:

 Atomic.Long id = Atomic.getLong("mapId"); map.put(id.getAndIncrement(), "something"); 

Atomic classes are designed primarily as building blocks for implementing non-blocking data structures and related infrastructure classes. The compareAndSet method is not a general replacement for locking. It applies only when critical updates for an object are confined to a single record.

Atomic classes are not general purpose replacements for java.lang.Integer and related classes. They do not define methods such as hashCode and compareTo. (Because atomic records are expected to be mutated, they are poor choices for hash table keys.) Additionally, classes are provided only for those types that are commonly useful in intended applications. Other types has to be wrapped into general Atomic.Var

You can also hold floats using java.lang.Float#floatToIntBits and java.lang.Float#intBitsToFloat conversions, and doubles using java.lang.Double#doubleToLongBits and java.lang.Double#longBitsToDouble conversions.

A scalable concurrent {@link ConcurrentNavigableMap} implementation. The map is sorted according to the {@linkplain Comparable natural ordering} of its keys, or by a {@link Comparator} provided at map creation time.

Java code for BTreeMap. Mostly performance sensitive code.

Compilation Configuration. Uses dead code elimination to remove `if(CONSTANT){code}` blocks

Concurrency aware, can verify that its configuration is thread safe

A database with easy access to named maps and other collections.

Various IO classes and utilities..

Used for serialization

Output of serialization

Concurrent HashMap which uses IndexTree for hash table

ArrayList like structure backed by tree

Primitive Sorted Map<Long,Long.

Extra methods for Map interface

Callback interface for MapExtra modification notifications.

Data streaming

FIFO Queue with option to remove element from middle

Callback interface for QueueLong

This interface specifies how Java Objects are serialized and de-serialized and also how objects are compared, hashed and tested for equality for use with MapDB.

Implementing classes do not have to be thread safe.

Read only Sorted Table Map. It stores data in table and uses binary search to find records

Stores records, mutable version

Binary operations performed on StoreBinary which retuns long

Store which uses binary storage (file, memory buffer...) and updates records on place. It has memory allocator, so it reuses space freed by deletes and updates.

Common utils for StoreDirect, StoreWAL and StoreCached

Stores records

Store which does not use serialization, but puts everything into on-heap Map.

Wraps Store and throws UnsupportedOperationException("Read-only") on operations which would modify it

Store which serializes its content into primitive Map<Long,byte[]>. It optionally persist its content into file, in this case it supports rollback and durability.

Stores records, transactional version

StoreDirect with write ahead log

Class can verify its status and data integrity: collections, Stores...

WAL shared between StoreWAL

Exception hierarchy for MapDB