继承类中的Java重写

我面临的问题是，每当有人想要.switchOff（）一个SmartDevice时，如果它是SmartFridge对象，它应该重写SmartDevice类中的switchOff（）方法

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问题是java给了我以下错误：操作符！=未为参数类型double定义，null

我不知道如何解决这个问题

@Override
public void switchOff() {
    if(this.getCurrentTemperature()!= null) {
            this.setSwitchedOn(true);
            //if the object is  SmartFridge leave switchedOn value to true

        }
    }

继承的类：

package SmartHomeApp;

public class SmartFridge extends SmartDevice{

    private double currentTemperature;


    public SmartFridge(String name, double location, boolean switchedOn, double currentTemperature)
    {

        super(name, location, switchedOn);
        setLocation(location);
        setName(name);
        setSwitchedOn(true);
        setCurrentTemperature(currentTemperature);
    }

    public double getCurrentTemperature(){ return currentTemperature;}
    public void setCurrentTemperature(double value){ currentTemperature = value;}

智能设备类别：

public class SmartDevice {
    private String name;
    private double location;
    private boolean switchedOn;

    public SmartDevice(String name, double location, boolean switchedOn) {
        setName(name);
        setLocation(location);
        setSwitchedOn(switchedOn);
    }

    //YOU CANT ACCESS the 'private classes' so you need to GET them
    public void setName(String value) {name = value;}
    public void setLocation(double value) {location = value;}
    public void setSwitchedOn(boolean value) {switchedOn = value;}

    public String getName() {return name;}
    public double getLocation() {return location;}
    public boolean getSwitchedOn() {return switchedOn;}

    public void switchOn() {this.switchedOn=true;}
    public void switchOff() {this.switchedOn=false;}

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检查“null”的类型不是对象。这种类型是原语，Java为它们设置默认值

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您应该查看本文以了解更多信息：

“运算符！=对于参数类型double，null未定义”-函数

getCurrentTemperature

返回

double

，该函数不能为null。所以不能将其与null进行比较。double是原语，而不是对象。你可以用Double来代替。那么我如何检查这个对象是否为空呢？（上面没有currentTemp变量）什么是“空”？如果0为“空”，如果温度实际上为0怎么办？“没有温度”吗？@luk2302我有一个智能家居，可以容纳智能设备和智能冰箱。假设我执行switchOff（）方法。该方法如何检查其智能设备还是智能冰箱？