1. ( ) ;'.
Strategy
@daisuke_m
2011/04/25

2. • @daisuke_m
• @j5ik2o
•
• Java
• Jiemamy
• Apache Mahout

3. Strategy
•
•
•
• ( )
→

4. • …

5. http://ja.wikipedia.org/
wiki/Strategy_

6. " "
• java.io.File

7. " "
• java.io.File

8. " "
• java.io.File

9. " "
• java.io.File

10. " "
• java.io.File

11. File
•…
• …
•
• …
• file1, file2, file10 …

12. Strategy
• case1 :
•
• case2 : if elseif elseif…
•

13. /* case1 */
void sort(List<File> target) {
// sort by name
}
/* case2 */
void sort(List<File> target, String type) {
if ("name".equasls(type)) {
// sort by name
} else if ("size".equals(type)) {
// sort by size
} else {
// default ...
}
}

14. Strategy
• case 3 : ( )
•
• case 4 :
•

20. •" "

21. Strategy
•
•
•
•
• →
• SQL → RDBMS
•

22. public interface Strategy {
String process(int i);
}
public class Client {
Strategy strategy;
public Client(Strategy strategy) {
this.strategy = strategy;
}
public void run() {
for (int i = 1; i <= 100; i++) {
System.out.println(strategy.process(i);
}
}
}

23. /* FizzBuzz */
public class FizzBuzzStrategy implements Strategy {
public String process(int i) {
if (i % 3 == 0 && i % 5 == 0) return "FizzBuzz";
if (i % 3 == 0) return "Fizz";
if (i % 5 == 0) return "Buzz";
return String.valueOf(i);
}
}
/* Nabeatsu */
public class NabeatsuStrategy implements Strategy {
public String process(int i) {
if (i % 3 == 0 || String.valueOf(i).contains("3")) {
return i + " ( ´Д` ) ";;
}
return String.valueOf(i);
}
}

24. Client c = new Client( );
c.run();
new FizzBuzzStrategy() new NabeatsuStrategy()
FizzBuzz Nabeatsu
1 1
2 2
Fizz 3 ( ´Д` )
4 4
Buzz 5
Fizz 6 ( ´Д` )
7 7
8 8
9 ( ´Д` )
Fizz
Buzz 10
11 11
12 ( ´Д` )
Fizz
13 13 ( ´Д` )