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fsm

fsm is a library to create finite state machines on the JVM.

A finite-state machine (FSM) or finite-state automaton (FSA, plural: automata), finite automaton, or simply a state machine, is a mathematical model of computation. It is an abstract machine that can be in exactly one of a finite number of states at any given time. The FSM can change from one state to another in response to some inputs; the change from one state to another is called a transition. An FSM is defined by a list of its states, its initial state, and the inputs that trigger each transition.

From Finite state machine on Wikipedia

Add Dependency

First make sure to register this Git repository as a Maven repository. Check the documentation for using a published package on GitHub if you are unsure how to do it.

Then include the dependency in your build.gradle(.kts) file.

implementation("io.nexure:fsm:3.0.0")

Usage

Here is a fictional example of what a state machine could look like that models the process of a payment. In summary, it has

  • Initial state CREATED
  • Intermediary states PENDING and AUTHORIZED
  • Terminal states SETTLED and REFUSED
stateDiagram-v2
    [*] --> CREATED
    CREATED --> PENDING: Submitted by consumer
    PENDING --> AUTHORIZED: Authorized by bank
    PENDING --> REFUSED: Refused by bank
    AUTHORIZED --> SETTLED: Funds moved
    SETTLED --> [*]
    REFUSED --> [*]
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See ExampleStateMachineTest.kt for an example of how a state machine with the above states and transitions is built, and how it can be invoked to execute certain actions on state transition.