State Pattern

State is useful when the question is not “which algorithm did the caller choose?” but “what does this operation mean in the object’s current state?”

This is a good fit for Java domains such as:

• order lifecycles
• workflow stages
• connection states
• UI modes

The pattern becomes valuable when conditional logic based on state starts to spread across methods and classes. It is weaker when the lifecycle is trivial and a few well-named conditionals remain clearer.

In this section

• Implementing State in Java
  Implement State in Java by moving state-specific behavior out of sprawling conditionals and into explicit state objects or state models.
• Context and State Classes in the State Pattern
  Design Java State contexts and state types so responsibilities stay explicit and transitions remain understandable.
• State vs. Strategy Pattern
  Compare State and Strategy in Java so caller-selected algorithms and lifecycle-driven behavior changes do not get confused.
• State Pattern Use Cases and Examples in Java
  See where State genuinely helps in Java systems, especially around lifecycle-rich domains such as orders, workflows, connections, and UI modes.