feat(chap07): Make example code as proxy pattern

spring5/sp5-chap07/pom.xml

+<?xml version="1.0" encoding="UTF-8" ?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0
+http://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+  <groupId>sp5</groupId>
+  <artifactId>sp5-chap07</artifactId>
+  <version>0.0.1-SNAPSHOT</version>
+
+  <dependencies>
+    <dependency>
+      <groupId>org.springframework</groupId>
+      <artifactId>spring-context</artifactId>
+      <version>5.0.2.RELEASE</version>
+    </dependency>
+    <dependency>
+      <groupId>org.aspectj</groupId>
+      <artifactId>aspectjweaver</artifactId>
+      <version>1.8.13</version>
+    </dependency>
+  </dependencies>
+
+  <build>
+    <plugins>
+      <plugin>
+
+        <artifactId>maven-compiler-plugin</artifactId>
+        <version>3.7.0</version>
+        <configuration>
+          <source>1.8</source>
+          <target>1.8</target>
+          <encoding>UTF-8</encoding>
+        </configuration>
+      </plugin>
+    </plugins>
+  </build>
+</project>
+

spring5/sp5-chap07/src/main/java/chap07/Calculator.java

+package main.java.chap07;
+
+public interface Calculator {
+    public long factorial(long num);
+}

spring5/sp5-chap07/src/main/java/chap07/ExecutiveTimeCalculator.java

+package main.java.chap07;
+
+public class ExecutiveTimeCalculator implements Calculator {
+
+    private Calculator delegate;
+
+    public ExecutiveTimeCalculator(Calculator delegate) {
+        this.delegate = delegate;
+    }
+
+    @Override
+    public long factorial(long num) {
+        long start = System.nanoTime();
+        long result = delegate.factorial(num);
+        long end = System.nanoTime();
+        System.out.printf("%s.factorial(%d) runtime = %d\n",
+            delegate.getClass().getSimpleName(),
+            num,
+            (end - start));
+        return result;
+    }
+
+}

spring5/sp5-chap07/src/main/java/chap07/ImplementCalculator.java

+package main.java.chap07;
+
+public class ImplementCalculator implements Calculator {
+
+    @Override
+    public long factorial(long num) {
+        long result = 1;
+        for (long i = 1; i <= num; i++) {
+            result *= i;
+        }
+        return result;
+    }
+}

spring5/sp5-chap07/src/main/java/chap07/MainProxy.java

+package main.java.chap07;
+
+public class MainProxy {
+
+    public static void main(String[] args) {
+        ExecutiveTimeCalculator timeToCalculator1 =
+            new ExecutiveTimeCalculator(new ImplementCalculator());
+        System.out.println(timeToCalculator1.factorial(20));
+
+        ExecutiveTimeCalculator timeToCalculator2 =
+            new ExecutiveTimeCalculator(new ImplementCalculator());
+        System.out.println(timeToCalculator2.factorial(3));
+    }
+
+}

spring5/sp5-chap07/src/main/java/chap07/ReCalculator.java

+package main.java.chap07;
+
+public class ReCalculator implements Calculator {
+    
+    @Override
+    public long factorial(long num) {
+        if (num == 0) {
+            return 1;
+        } else {
+            return num * factorial(num - 1);
+        }
+    }
+}