BAEL-1997 different example code

patterns/design-patterns/src/main/java/com/baeldung/state/DeliveredState.java

@@ -0,0 +1,19 @@
+package com.baeldung.state;
+
+public class DeliveredState implements PackageState {
+
+    @Override
+    public void next(Package pkg) {
+        pkg.setState(new ReceivedState());
+    }
+
+    @Override
+    public void prev(Package pkg) {
+        pkg.setState(new OrderedState());
+    }
+
+    @Override
+    public String toString() {
+        return "DeliveredState{}";
+    }
+}

patterns/design-patterns/src/main/java/com/baeldung/state/ExplicitStateDemo.java

@@ -1,21 +0,0 @@
-package com.baeldung.state;
-
-import com.baeldung.state.context.TradeContext;
-import com.baeldung.state.states.DayTradeBehavior;
-import com.baeldung.state.states.PositionTradeBehavior;
-import com.baeldung.state.states.SwingTradeBehavior;
-
-public class ExplicitStateDemo {
-
-    public static void main(String[] args) {
-
-        TradeContext tradeContext = new TradeContext(new SwingTradeBehavior());
-        tradeContext.trade();
-
-        tradeContext.setBehavior(new PositionTradeBehavior());
-        tradeContext.trade();
-
-        tradeContext.setBehavior(new DayTradeBehavior());
-        tradeContext.trade();
-    }
-}

patterns/design-patterns/src/main/java/com/baeldung/state/InternalStateDemo.java

@@ -1,15 +0,0 @@
-package com.baeldung.state;
-
-import com.baeldung.state.context.TradeContext;
-import com.baeldung.state.states.FallbackDayTradeBehavior;
-
-public class InternalStateDemo {
-
-    public static void main(String[] args) {
-
-        TradeContext tradeContext = new TradeContext(new FallbackDayTradeBehavior());
-        tradeContext.trade();
-        tradeContext.trade();
-        tradeContext.trade();
-    }
-}

patterns/design-patterns/src/main/java/com/baeldung/state/OrderedState.java

@@ -0,0 +1,19 @@
+package com.baeldung.state;
+
+public class OrderedState implements PackageState {
+
+    @Override
+    public void next(Package pkg) {
+        pkg.setState(new DeliveredState());
+    }
+
+    @Override
+    public void prev(Package pkg) {
+        System.out.println("The package is in it's root state.");
+    }
+
+    @Override
+    public String toString() {
+        return "OrderedState{}";
+    }
+}

patterns/design-patterns/src/main/java/com/baeldung/state/Package.java

@@ -0,0 +1,22 @@
+package com.baeldung.state;
+
+public class Package {
+
+    private PackageState state = new OrderedState();
+
+    public PackageState getState() {
+        return state;
+    }
+
+    public void setState(PackageState state) {
+        this.state = state;
+    }
+
+    public void previousState() {
+        state.prev(this);
+    }
+
+    public void nextState() {
+        state.next(this);
+    }
+}

patterns/design-patterns/src/main/java/com/baeldung/state/PackageState.java

@@ -0,0 +1,8 @@
+package com.baeldung.state;
+
+public interface PackageState {
+
+    void next(Package pkg);
+
+    void prev(Package pkg);
+}

patterns/design-patterns/src/main/java/com/baeldung/state/ReceivedState.java

@@ -0,0 +1,23 @@
+package com.baeldung.state;
+
+public class ReceivedState implements PackageState {
+
+    @Override
+    public void next(Package pkg) {
+        if (pkg.getState() instanceof ReceivedState) {
+            System.out.println("This package is already received by a client.");
+            return;
+        }
+        pkg.setState(this);
+    }
+
+    @Override
+    public void prev(Package pkg) {
+        pkg.setState(new DeliveredState());
+    }
+
+    @Override
+    public String toString() {
+        return "ReceivedState{}";
+    }
+}

patterns/design-patterns/src/main/java/com/baeldung/state/context/TradeContext.java

@@ -1,29 +0,0 @@
-package com.baeldung.state.context;
-
-import com.baeldung.state.states.TradeBehavior;
-
-public class TradeContext {
-
-    private TradeBehavior behavior;
-
-    public TradeContext(TradeBehavior behavior) {
-        this.behavior = behavior;
-    }
-
-    public TradeBehavior getBehavior() {
-        return behavior;
-    }
-
-    public void setBehavior(TradeBehavior behavior) {
-        this.behavior = behavior;
-    }
-
-    public void trade() {
-        behavior.trade(this);
-    }
-
-    @Override
-    public String toString() {
-        return "TradeContext{" + "behavior=" + behavior + '}';
-    }
-}

patterns/design-patterns/src/main/java/com/baeldung/state/states/DayTradeBehavior.java

@@ -1,11 +0,0 @@
-package com.baeldung.state.states;
-
-import com.baeldung.state.context.TradeContext;
-
-public class DayTradeBehavior implements TradeBehavior {
-
-    @Override
-    public void trade(TradeContext ctx) {
-        System.out.println("Trading method: Day Trade");
-    }
-}

patterns/design-patterns/src/main/java/com/baeldung/state/states/FallbackDayTradeBehavior.java

@@ -1,16 +0,0 @@
-package com.baeldung.state.states;
-
-import com.baeldung.state.context.TradeContext;
-
-public class FallbackDayTradeBehavior implements TradeBehavior {
-
-    @Override
-    public void trade(TradeContext ctx) {
-        System.out.println("Trading method: Day Trade");
-
-        if (Math.random() > 0.4) {
-            ctx.setBehavior(new SwingTradeBehavior());
-            System.out.println("Day trading would not go well, falling back to Swing Trade");
-        }
-    }
-}

patterns/design-patterns/src/main/java/com/baeldung/state/states/PositionTradeBehavior.java

@@ -1,11 +0,0 @@
-package com.baeldung.state.states;
-
-import com.baeldung.state.context.TradeContext;
-
-public class PositionTradeBehavior implements TradeBehavior {
-
-    @Override
-    public void trade(TradeContext ctx) {
-        System.out.println("Trading method: Position Trade");
-    }
-}

patterns/design-patterns/src/main/java/com/baeldung/state/states/SwingTradeBehavior.java

@@ -1,11 +0,0 @@
-package com.baeldung.state.states;
-
-import com.baeldung.state.context.TradeContext;
-
-public class SwingTradeBehavior implements TradeBehavior {
-
-    @Override
-    public void trade(TradeContext ctx) {
-        System.out.println("Trading method: Swing Trade");
-    }
-}

patterns/design-patterns/src/main/java/com/baeldung/state/states/TradeBehavior.java

@@ -1,7 +0,0 @@
-package com.baeldung.state.states;
-
-import com.baeldung.state.context.TradeContext;
-
-public interface TradeBehavior {
-    void trade(TradeContext ctx);
-}

patterns/design-patterns/src/test/java/com/baeldung/state/StatePatternUnitTest.java

@@ -0,0 +1,33 @@
+package com.baeldung.state;
+
+import com.baeldung.state.Package;
+
+import static org.junit.Assert.assertThat;
+import static org.hamcrest.CoreMatchers.instanceOf;
+
+import org.junit.Test;
+
+public class StatePatternUnitTest {
+
+    @Test
+    public void givenNewPackage_whenPackageReceived_thenStateReceived() {
+        Package pkg = new Package();
+
+        assertThat(pkg.getState(), instanceOf(OrderedState.class));
+        pkg.nextState();
+
+        assertThat(pkg.getState(), instanceOf(DeliveredState.class));
+        pkg.nextState();
+
+        assertThat(pkg.getState(), instanceOf(ReceivedState.class));
+    }
+
+    @Test
+    public void givenDeliveredPackage_whenPrevState_thenStateOrdered() {
+        Package pkg = new Package();
+        pkg.setState(new DeliveredState());
+        pkg.previousState();
+
+        assertThat(pkg.getState(), instanceOf(OrderedState.class));
+    }
+}