cd2a2e7711
* Moves saga to Java 11 * Moves semaphore to Java 11 * Moves servant to Java 11 * Moves serverless to Java 11 * Moves service-layer to Java 11 * Moves service-locator to Java 11 * Moves sharding to Java 11 * Moves singleton to Java 11 * Moves spatial-partition to Java 11 * Moves specification to Java 11 * Moves state to Java 11 * Moves step-builder to Java 11 * Moves strategy to Java 11 * Moves subclass-sandbox to Java 11 * Fixes checkstyle issues
layout, title, folder, permalink, categories, tags
| layout | title | folder | permalink | categories | tags | |
|---|---|---|---|---|---|---|
| pattern | State | state | /patterns/state/ | Behavioral |
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Also known as
Objects for States
Intent
Allow an object to alter its behavior when its internal state changes. The object will appear to change its class.
Class diagram
Applicability
Use the State pattern in either of the following cases
- An object's behavior depends on its state, and it must change its behavior at run-time depending on that state
- Operations have large, multipart conditional statements that depend on the object's state. This state is usually represented by one or more enumerated constants. Often, several operations will contain this same conditional structure. The State pattern puts each branch of the conditional in a separate class. This lets you treat the object's state as an object in its own right that can vary independently from other objects.
Real world examples
- javax.faces.lifecycle.Lifecycle#execute() controlled by FacesServlet, the behavior is dependent on current phase of lifecycle.
- JDiameter - Diameter State Machine