策略模式

package strategy;

public class Example {
	public Double calRecharge(Double charge, RechargeTypeEnum type) {
		if (type.equals(RechargeTypeEnum.E_BANK)) {
			return charge * 0.85;
		} else if (type.equals(RechargeTypeEnum.BUSI_ACCOUNTS)) {
			return charge * 0.90;
		} else if (type.equals(RechargeTypeEnum.MOBILE)) {
			return charge;
		} else if (type.equals(RechargeTypeEnum.CARD_RECHARGE)) {
			return charge + charge * 0.01;
		} else {
			return null;
		}
	}
}

package strategy;

public enum RechargeTypeEnum {
E_BANK(1, '网银'),
BUSI_ACCOUNTS(2, '商户账号'),
MOBILE(3,'手机卡充值'),
CARD_RECHARGE(4,'充值卡')
;
private int value;
private String description;
private RechargeTypeEnum(int value, String description) {
this.value = value;
this.description = description;
}
public int value() {
return value;
}
public String description() {
return description;
}
public static RechargeTypeEnum valueOf(int value) {
for(RechargeTypeEnum type : RechargeTypeEnum.values()) {
if(type.value() == value) {
return type;
}
}
return null;
}
}可以看出上面四种不同的计算方式在一个方法内部，不利于扩展和维护，当然也不符合面向对象设计原则。对以上的代码利用策略模式进行修改，类图如下：http:// dl2.iteye.com/upload/attachment/0087/8886/3ca5e83f-f6ad-3c77-a320-e716f5c3b639.png
实例代码如下：Java代码 package strategy.strategy;

import strategy.RechargeTypeEnum;

public interface Strategy {
	public Double calRecharge(Double charge, RechargeTypeEnum type);
}

package strategy.strategy;
import strategy.RechargeTypeEnum;

public class EBankStrategy implements Strategy {
	@Override
	public Double calRecharge(Double charge, RechargeTypeEnum type) {
		return charge * 0.85;
	}
}

package strategy.strategy;
import strategy.RechargeTypeEnum;

public class BusiAcctStrategy implements Strategy {
	@Override
	public Double calRecharge(Double charge, RechargeTypeEnum type) {
		// TODO Auto-generated method stub
		return charge * 0.90;
	}
}

package strategy.strategy;
import strategy.RechargeTypeEnum;

public class MobileStrategy implements Strategy {
	@Override
	public Double calRecharge(Double charge, RechargeTypeEnum type) {
		// TODO Auto-generated method stub
		return charge;
	}
}

package strategy.strategy;
import strategy.RechargeTypeEnum;

public class CardStrategy implements Strategy {
	@Override
	public Double calRecharge(Double charge, RechargeTypeEnum type) {
		return charge + charge * 0.01;
	}
}

package strategy.strategy;
import strategy.RechargeTypeEnum;

public class Context {
	private Strategy strategy;

	public Double calRecharge(Double charge, Integer type) {
		strategy = StrategyFactory.getInstance().creator(type);
		return strategy.calRecharge(charge, RechargeTypeEnum.valueOf(type));
	}

	public Strategy getStrategy() {
		return strategy;
	}

	public void setStrategy(Strategy strategy) {
		this.strategy = strategy;
	}
}

package strategy.strategy;
import java.util.HashMap;
import java.util.Map;
import strategy.RechargeTypeEnum;

public class StrategyFactory {
	private static StrategyFactory factory = new StrategyFactory();

	private StrategyFactory() {
	}

	private static Map strategyMap = new HashMap<>();
	static {
		strategyMap.put(RechargeTypeEnum.E_BANK.value(), new EBankStrategy());
		strategyMap.put(RechargeTypeEnum.BUSI_ACCOUNTS.value(), new BusiAcctStrategy());
		strategyMap.put(RechargeTypeEnum.MOBILE.value(), new MobileStrategy());
		strategyMap.put(RechargeTypeEnum.CARD_RECHARGE.value(), new CardStrategy());
	}

	public Strategy creator(Integer type) {
		return strategyMap.get(type);
	}

	public static StrategyFactory getInstance() {
		return factory;
	}
}

package strategy.strategy;

import strategy.RechargeTypeEnum;

public class Client {
public static void main(String[] args) {
Context context = new Context();
// 网银充值100 需要付多少
Double money = context.calRecharge(100D,
RechargeTypeEnum.E_BANK.value());
System.out.println(money);
// 商户账户充值100 需要付多少
Double money2 = context.calRecharge(100D,
RechargeTypeEnum.BUSI_ACCOUNTS.value());
System.out.println(money2);
// 手机充值100 需要付多少
Double money3 = context.calRecharge(100D,
RechargeTypeEnum.MOBILE.value());
System.out.println(money3);
// 充值卡充值100 需要付多少
Double money4 = context.calRecharge(100D,
RechargeTypeEnum.CARD_RECHARGE.value());
System.out.println(money4);
}
}