ATM on FSM

Simple example of Finite-State Machines on Automated Teller Machine of some Bank

Written on Java with Polymorphism form

Main idea

Inspired by course of Program Principles 2 by @Beisenbek

Return to the idea of FSM after two years :)

All states are singleton classes with access to database and machine data. Have .next() method for each state. Only some states are final.

FSM schema

States

Start

• s - request PIN

Finish

• h - session finished
• e - session finished with error

Intermediate

• q₀ - choose option in main menu
• q₁ - making transaction
• q₂ - enter sum to withdraw
• q₃ - output account cash
• q₄ - enter cash to replenish
• q₅ - enter sum and account to transfer
• q₆ - enter a pin to change

Actions

Pins

• p₀ - wrong PIN
• p₁ - correct PIN

Menu

• m₀ - returning to menu
• m₁ - choosing invalid option at menu

Finishing

• e₀ - finishing session
• e₁ - system error

Other

• z₀ - choosing to withdraw cash
• z₁ - asserting withdrawing
• z₂ - checking account
• z₃ - choosing to replenish cash
• z₄ - asserting replenish
• z₅ - enter sum again
• z₆ - choosing to transfer sum
• z₇ - asserting transfer
• z₈ - enter account again
• z₉ - choosing change pin
• z₁₀ - enter a pin again (wrong pin)

JSON schema

Schema can be opened via this link