if/else问题解决（二）策略模式+工厂方法消除

一、案例

假设需求为，根据类型，处理相对应的操作，优化前有以下代码：

  public void operation(String type){
        if("add".equals(type)){
            //执行加法
        }else if("sub".equals(type)){
            //执行减法
        }
        //这里还有很多操作
    }

二、方案

1、定义接口

public interface OperationService {
    Integer operation(Integer num1, Integer num2);

    String getType();
}

2、实现各个逻辑策略实现类

public class AddOperationImpl implements OperationService {

    @Override
    public Integer operation(Integer num1, Integer num2) {
        return num1 + num2;
    }

    @Override
    public String getType() {
        return "add";
    }
}

public class SubOperationImpl implements OperationService {

    @Override
    public Integer operation(Integer num1, Integer num2) {
        return num1 - num2;
    }

    @Override
    public String getType() {
        return "sub";
    }
}

3、编写策略工厂类

public class OperationServicesFactory {

    private static final Map<String, OperationService> map = new HashMap<>();
    static {
        map.put("add", new AddOperationImpl());
        map.put("sub", new SubOperationImpl());
    }

    public static OperationService getOperationService(String type) {
        return map.get(type);
    }

}

4、最终测试

   public static void main(String[] args) {
        String type="add";
        OperationService operation = OperationServicesFactory.getOperationService("type");
        System.out.println(operation.operation(1, 2));
    }