add facade DP

Liu Yuning · Liu Yuning · commit 8bb1706af551 · 2017-05-18T23:00:24.000+08:00
diff --git a/src/designpattern/facade/Facade.java b/src/designpattern/facade/Facade.java
@@ -0,0 +1,36 @@
+package designpattern.facade;
+
+/**
+ * 外观类，它需要了解所有的子系统的方法或属性，进行组合，以备外界调用
+ * 
+ * @author liu yuning
+ *
+ */
+public class Facade {
+    SubSystemOne subSystemOne;
+    SubSystemTwo subSystemTwo;
+    SubSystemThree subSystemThree;
+    SubSystemFour subSystemFour;
+
+    public Facade() {
+	subSystemOne = new SubSystemOne();
+	subSystemTwo = new SubSystemTwo();
+	subSystemThree = new SubSystemThree();
+	subSystemFour = new SubSystemFour();
+    }
+
+    public void methodA() {
+	System.out.println("方法组A:");
+
+	subSystemOne.methodOne();
+	subSystemTwo.methodTwo();
+	subSystemFour.methodFour();
+    }
+
+    public void methodB() {
+	System.out.println("方法组B:");
+
+	subSystemThree.methodThree();
+	subSystemFour.methodFour();
+    }
+}
diff --git a/src/designpattern/facade/FacadeClient.java b/src/designpattern/facade/FacadeClient.java
@@ -0,0 +1,20 @@
+package designpattern.facade;
+
+/**
+ * 外观类客户端
+ * 
+ * @author liu yuning
+ *
+ */
+public class FacadeClient {
+    public static void main(String[] args) {
+	// 由于Facade的作用，客户端可以根本不知道四个子系统的存在
+	// 启发：维护一个遗留的大型系统时，可能这个系统已经非常难以维护和扩展了，此时可以
+	// 为新系统开发一个外观Facade类，来提供设计粗糙或高度复杂的遗留代码的比较清晰简单
+	// 的接口，让新系统与Facade对象交互，Facade与遗留代码交互所有复杂的工作
+	Facade facade = new Facade();
+
+	facade.methodA();
+	facade.methodB();
+    }
+}
diff --git a/src/designpattern/facade/SystemInterface.java b/src/designpattern/facade/SystemInterface.java
@@ -0,0 +1,35 @@
+package designpattern.facade;
+
+/**
+ * “系统”接口，只是标记接口，暂无任何意义
+ * 
+ * @author liu yuning
+ *
+ */
+public interface SystemInterface {
+
+}
+
+class SubSystemOne implements SystemInterface {
+    public void methodOne() {
+	System.out.println("子系统方法一");
+    }
+}
+
+class SubSystemTwo implements SystemInterface {
+    public void methodTwo() {
+	System.out.println("子系统方法二");
+    }
+}
+
+class SubSystemThree implements SystemInterface {
+    public void methodThree() {
+	System.out.println("子系统方法三");
+    }
+}
+
+class SubSystemFour implements SystemInterface {
+    public void methodFour() {
+	System.out.println("子系统方法四");
+    }
+}
