策略与适配器设计模式

1、策略设计模式

import java.util.Arrays;

public class Apply {
	public static void process(Processor p, Object s) {
		System.out.println("Using processor " + p.name());
		System.out.println(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);
	}
}

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

	Object process(Object input) {
		return input;
	}
}

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

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

class Splitter extends Processor {
	String process(Object input) {
		return (Arrays.toString(((String) input).split(" ")));
	}
}

　　输出：

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]

分析：对于不同的processor对象（即策略），应用于字符串s会产生不同的行为。

2、适配器设计模式

import java.util.Arrays;

public class Adapter {
	public static void process(Processor p, Object s) {
		System.out.println("Using processor " + p.name());
		System.out.println(p.process(s));
	}

	public static void main(String[] args) {
		String s = "abcdefg";
		process(new ExerAdapter(new Exer()), s);
	}
}

interface Processor {
	String name();

	Object process(Object input);
}

class Exer {
	String func(String s) {
		if (s != null && s != "") {
			char[] split = s.toCharArray();
			for (int i = 0; i < split.length - 1; i += 2) {
				char temp = split[i];
				split[i] = split[i + 1];
				split[i + 1] = temp;
			}
			s = Arrays.toString(split);
		}
		return s;
	}
}

/**
 * 适配器转换类
 */
class ExerAdapter implements Processor {

	Exer e;

	public ExerAdapter(Exer e) {
		this.e = e;
	}

	@Override
	public String name() {
		return e.getClass().getSimpleName();
	}

	@Override
	public Object process(Object input) {
		return e.func((String) input);
	}

}

　　输出：

Using processor Exer
[b, a, d, c, f, e, g]

分析：由于Exer与Process接口不一致，所以新增一个ExerAdapter适配器类来对Exer适配，应用于Adapter的process方法。