你有一個(gè)類型碼,它會影響類的行為,但你無法通過繼承手法消除它. 以狀態(tài)對象取代類型碼.

如果你的宿主對象不能繼承或是類型碼的值在對象的生命周期中發(fā)生變化,那么可以使用本重構(gòu);

1. 新建一個(gè)類以類型碼命名 這是狀態(tài)對象,并創(chuàng)建他的子類,重寫狀態(tài)碼的方法;
2. 在宿主類,組合生成對象.并且用多態(tài)對象返回狀態(tài)碼,使用這個(gè)多態(tài)對象來調(diào)用子類的方法;

public class Employee {
    private int type;
//    public static final int ENGINEER = 0;
//    public static final int SALEMAN = 1;
//    public static final int MANAGER = 2;
    private EmployeeType mEmployeeType;

    public Employee(int type) {
//        setType(type);
        mEmployeeType= EmployeeType.newType(type);
    }

    public int getType() {
//        return type;
        return mEmployeeType.getTypeCode();
    }

//    }

    //    public void setType(int type) {
////        this.type = type;
//        switch (type) {
//            case ENGINEER:
//                mEmployeeType = new Engineer();
//                break;
//            case SALEMAN:
//                mEmployeeType = new SaleMan();
//                break;
//            case MANAGER:
//                mEmployeeType = new Manager();
//                break;
//            default:
//                throw new RuntimeException("Incorrect Employee code");
//        }
    int payAmount() {
        switch (getType()) {
            case ENGINEER:
                return 100;
            case SALEMAN:
                return 200;
            case MANAGER:
                return 1000;
            default:
                throw new RuntimeException("Incorrect Employee");
        }
    }





    public static void main(String[] args) {
        Employee engineerEmployee = new Employee(ENGINEER);
        engineerEmployee.payAmount();
        System.out.println(engineerEmployee.payAmount());
        Employee salemanEmployee = new Employee(SALEMAN);
        System.out.println(salemanEmployee.payAmount());
        Employee managerEmployee = new Employee(MANAGER);
        managerEmployee.payAmount();

    }
}



public abstract class EmployeeType {
    abstract int getTypeCode();

    static final int ENGINEER = 0;
    static final int SALEMAN = 1;
    static final int MANAGER = 2;

    public static EmployeeType newType(int code) {
        switch (code) {
            case ENGINEER:
                return new Engineer();
            case SALEMAN:
                return new SaleMan();
            case MANAGER:
                return new Manager();
            default:
                throw new IllegalArgumentException("Incorrect Employee code");
        }
    }
}


public class Engineer extends EmployeeType {
    @Override
    int getTypeCode() {
        return ENGINEER;
    }
}
public class Manager extends EmployeeType {
    @Override
    int getTypeCode() {
        return MANAGER;
    }
}
public class SaleMan extends EmployeeType {
    @Override
    int getTypeCode() {
        return SALEMAN;
    }
}