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FatherOfFiveChildren
Asked:2020-10-25 11:46:53 +0000 UTC2020-10-25 11:46:53 +0000 UTC

如何覆盖内部类方法？

  • 772

有一个带有内部类的类：

public class ParentClass  {

    //состояние объекта
    public class State  {
        public void action(){}
    }  
    public State currentState;
    public void setState(int stateID)  {
        if(stateID==0) currentState = new Born();
        if(stateID==1) currentState = new Life();
        if(stateID==2) currentState = new Dead();
    }  

    //виды состояний
    public class Born extends State    {
        @Overide
        public void action(){}
    }
    public class Life extends State  {
        @Overide
        public void action(){}
    }
    public class Dead extends State  {}
        @Overide
        public void action(){}
    }

    ///уделяем объекту внимание
    public void Action  (){
        currentState.action();
    } 
}

如何在不继承类本身的情况下覆盖继承人内部类 Born Life 和 Dead 的方法？

Задумка была простой  
1. Обеспечить каждого наследника своей реализацией методов action(). 
2. Оставить метод переключений состояния объекта setState() в родителе.
java

3 个回答

  1. public class ChildClass extends ParentClass {
    class ChildInner extends ParentClass.ClassBorn {
        public void action() {}
    }
}

    在您的示例中，不是本地课程，而是内部课程。

    • 3
  2. Best Answer

    如果我理解正确，它是这样的：

    public class ParentClass {

    public State currentState;

    public void setState(int stateID) {
        if (stateID == 0) currentState = new Born() {
            @Override
            public void action() {
                // action for Born state
            }
        };

        if (stateID == 1) currentState = new Life() {
            @Override
            public void action() {
                // action for Life state
            }
        };

        if (stateID == 2) currentState = new Dead() {
            @Override
            public void action() {
                // action for Dead state
            }
        };
    }

    //состояние объекта
    public class State {
        public void action() {
        }
    }

    //виды состояний
    public class Born extends State {
    }

    public class Life extends State {
    }

    public class Dead extends State {

        ///уделяем объекту внимание
        public void Action() {
            currentState.action();
        }
    }
}

    或者一般是这样的：

    public class ParentClass {

    public State currentState;

    public void setState(int stateID) {
        if (stateID == 0) currentState = new State() {
            @Override
            public void action() {
                // action for Born state
            }
        };

        if (stateID == 1) currentState = new State() {
            @Override
            public void action() {
                // action for Life state
            }
        };

        if (stateID == 2) currentState = new State() {
            @Override
            public void action() {
                // action for Dead state
            }
        };
    }

    ///уделяем объекту внимание
    public void Action() {
        currentState.action();
    }

    //состояние объекта
    public class State {
        public void action() {
        }
    }
}

    但总的来说，该模式State最好以稍微不同的方式实现。

    • 1

  3. 我将如何实现该模式State

    public interface MotorState {
    void on(Motor motor);
    void off(Motor motor);
}

    2种状态，如开和关：

    public class MotorOn implements MotorState {

    @Override
    public void on(Motor motor) {
        System.out.println("Motor is already on");
    }

    @Override
    public void off(Motor motor) {
        motor.setState(new MotorOff());
        System.out.println("Motor is off");
    }

    @Override
    public String toString() {
        return "Motor is on";
    }
}

public class MotorOff implements MotorState {

    @Override
    public void on(Motor motor) {
        motor.setState(new MotorOn());
        System.out.println("Motor is on");
    }

    @Override
    public void off(Motor motor) {
        System.out.println("Motor is already off");
    }

    @Override
    public String toString() {
        return "Motor is off";
    }
}

    电机本身：

    public class Motor {
    private MotorState state;

    public Motor() {
        this.state = new MotorOff();
    }

    public MotorState getState() {
        return state;
    }

    public void setState(MotorState newState) {
        this.state = newState;
    }

    public void turnOn() {
        state.on(this);
    }

    public void turnOff() {
        state.off(this);
    }

    public boolean isOn() {
        return state instanceof MotorOn;
    }
}
    • 1

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