add state DP

Liu Yuning · Liu Yuning · commit d7c37a15c806 · 2017-05-19T23:11:43.000+08:00
diff --git a/src/designpattern/state/Context.java b/src/designpattern/state/Context.java
@@ -0,0 +1,27 @@
+package designpattern.state;
+
+/**
+ * Context类，维护一个ConcreteState子类的实例，这个实例定义当前的状态
+ * 
+ * @author liu yuning
+ *
+ */
+public class Context {
+    private State state;
+
+    public Context(State state) {
+	this.state = state;
+    }
+
+    public State getState() {
+	return state;
+    }
+
+    public void setState(State state) {
+	this.state = state;
+    }
+
+    public void request() {
+	this.state.handle(this);
+    }
+}
diff --git a/src/designpattern/state/State.java b/src/designpattern/state/State.java
@@ -0,0 +1,44 @@
+package designpattern.state;
+
+/**
+ * 抽象状态类
+ * 
+ * @author liu yuning
+ *
+ */
+public abstract class State {
+    public abstract void handle(Context context);
+
+}
+
+class ConcreteStateA extends State {
+
+    @Override
+    public void handle(Context context) {
+	System.out.println("现在是在状态A");
+	context.setState(new ConcreteStateB());
+    }
+
+}
+
+class ConcreteStateB extends State {
+
+    @Override
+    public void handle(Context context) {
+	System.out.println("现在是在状态B");
+	context.setState(new ConcreteStateC());
+
+    }
+
+}
+
+class ConcreteStateC extends State {
+
+    @Override
+    public void handle(Context context) {
+	System.out.println("现在是在状态C");
+	context.setState(new ConcreteStateA());
+
+    }
+
+}
diff --git a/src/designpattern/state/StateClient.java b/src/designpattern/state/StateClient.java
@@ -0,0 +1,20 @@
+package designpattern.state;
+
+/**
+ * 客户端：不断请求，不断更改状态
+ * 
+ * @author liu yuning
+ *
+ */
+public class StateClient {
+    public static void main(String[] args) {
+
+	Context context = new Context(new ConcreteStateA());
+
+	context.request();
+	context.request();
+	context.request();
+	context.request();
+	context.request();
+    }
+}
