diff --git a/03-behavioral/state/README.md b/03-behavioral/state/README.md
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+# State Design Pattern — Java Example
+
+**Pattern:** Behavioral → State
+**Article:** https://ankurm.com/state-design-pattern-java/
+
+## What this example shows
+
+A traffic light with zero if-else state machines. `TrafficLightState` declares what every state must do: handle entry (`onEnter`), handle the transition trigger (`next`), and report its own color. `TrafficLight` is the context — it holds a reference to the current state and delegates every call to it. `RedState`, `GreenState`, and `YellowState` each know only their own entry message and their own next state (Red→Green→Yellow→Red); none of them knows about the full cycle. `Main` creates the light, cycles through six transitions, and prints why this beats a single class full of if-else branches.
+
+## How to run
+
+```bash
+javac state/*.java -d out/state
+java -cp out/state state.Main
+```
+
+Requires Java 25.
+
+## Post Section ↔ File Mapping
+
+| Post Section | File(s) |
+|---|---|
+| With State: Traffic Light — the State interface | `TrafficLightState.java` |
+| With State: Traffic Light — the Context | `TrafficLight.java` |
+| With State: Traffic Light — RedState | `RedState.java` |
+| With State: Traffic Light — GreenState | `GreenState.java` |
+| With State: Traffic Light — YellowState | `YellowState.java` |
+| With State: Traffic Light — wiring it together | `Main.java` |
+
+Note: the "Without State: The if-else Machine" snippet (the fragile `TrafficLight` with a `String state` field) is illustrative only — it is not part of this repository's runnable example.
+
+Article: https://ankurm.com/state-design-pattern-java/
+All patterns: https://ankurm.com/design-patterns-java/
diff --git a/README.md b/README.md
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--- a/README.md
+++ b/README.md
@@ -407,6 +407,25 @@ javac 03-behavioral/observer/*.java -d out/observer
 java -cp out/observer observer.Main
 ```
 
+### State (`03-behavioral/state/`)
+
+| Post Section | File(s) |
+|---|---|
+| With State: Traffic Light — the State interface | `TrafficLightState.java` |
+| With State: Traffic Light — the Context | `TrafficLight.java` |
+| With State: Traffic Light — RedState | `RedState.java` |
+| With State: Traffic Light — GreenState | `GreenState.java` |
+| With State: Traffic Light — YellowState | `YellowState.java` |
+| With State: Traffic Light — wiring it together | `Main.java` |
+
+Note: the "Without State: The if-else Machine" snippet is illustrative only — it is not part of this repository's runnable example.
+
+Run it:
+```bash
+javac 03-behavioral/state/*.java -d out/state
+java -cp out/state state.Main
+```
+
 ## Reference
 
 - *Design Patterns: Elements of Reusable Object-Oriented Software* — Gamma, Helm, Johnson, Vlissides