java 完全解耦

只要有一个方法操作的是类而非接口,那么你就只能使用这个类及其子类,如果你想要将这个方法应用于不在此继承结构中的某个类,

//像本例这样,创建一个能够根据所传递的参数对象的不同而具有不同行为的方法,被称为策略设计
//策略就是传递进去的参数对象,它包含要执行的代码
//: interfaces/classprocessor/Apply.java
package object;
import java.util.*;
import static net.mindview.util.Print.*;

class Processor {
  public String name() {
    return getClass().getSimpleName();
  }
  Object process(Object input) { return input; }
}    

class Upcase extends Processor {
  String process(Object input) { // Covariant return
    return ((String)input).toUpperCase();
  }
}

class Downcase extends Processor {
  String process(Object input) {
    return ((String)input).toLowerCase();
  }
}

class Splitter extends Processor {
  String process(Object input) {
    // The split() argument divides a String into pieces:
    return Arrays.toString(((String)input).split(" "));//split()返回String[]数组
  }
}    

public class Apply {
  public static void process(Processor p, Object s) {
    print("Using Processor " + p.name());
    print(p.process(s));
  }
  public static String s =
    "Disagreement with beliefs is by definition incorrect";
  public static void main(String[] args) {
    process(new Upcase(), s);
    process(new Downcase(), s);
    process(new Splitter(), s);
  }
} /* Output:
Using Processor Upcase
DISAGREEMENT WITH BELIEFS IS BY DEFINITION INCORRECT
Using Processor Downcase
disagreement with beliefs is by definition incorrect
Using Processor Splitter
[Disagreement, with, beliefs, is, by, definition, incorrect]
*///:~

那么你就会触霉头,接口可以在很大程度上放宽这种限制,因此,我们可以编写可服用性更好的代码