我在尝试弄清楚如何在AM FM和XM之间比较selectedRadio时遇到问题,以便我可以确定它当前在哪一个然后返回特定无线电的电台。我知道我需要equals方法我只是不确定正确的方法来使用它来获得我正在寻找的结果。
public class AutoRadioSystem
{
private Radio selectedRadio;
private AMRadio radioAM;
private FMRadio radioFM;
private XMRadio radioXM;
//I'm not sure if this is the correct way to do this so that selectedRadio equals the object of radioAM
public AutoRadioSystem()
{
selectedRadio = radioAM;
}
//trying to figure out how to compare if selectedRadio is one of these.
public double getCurrentStation()
{
if (selectedRadio == radioAM)
{
return radioAM.getCurrentStaion();
}
else if (selectedRadio == radioFM)
{
return radioFM.getCurrentStaion();
}
return 0.0;
}
// its supposed to switch the radio from AM to FM when this method is called
public void selectRadio()
{
if (selectedRadio.equals(radioAM))
selectedRadio = radioFM;
}
public boolean equals (Object o)
{
if (o == null)
return false;
if (! (o instanceof AutoRadioSystem))
return false;
AutoRadioSystem other = (AutoRadioSystem) o;
return this.selectedRadio == other.selectedRadio;
}
public static void main (String [] args) {
AutoRadioSystem c = new AutoRadioSystem();
c.selectRadio();
double b = c.getCurrentStation();
System.out.println(b);
}
}
public abstract class Radio
{
double currentStation;
RadioSelectionBar radioSelectionBar;
public Radio()
{
this.currentStation = getMin_Station();
}
public abstract double getMax_Station();
public abstract double getMin_Station();
public abstract double getIncrement();
public void up()
{
}
public void down()
{
}
public double getCurrentStaion()
{
return this.currentStation;
}
public void setCurrentStation(double freq)
{
this.currentStation = freq;
}
public void setStation(int buttonNumber, double station)
{
}
public double getStation(int buttonNumber)
{
return 0.0;
}
public String toString()
{
String message = ("" + currentStation);
return message;
}
public boolean equals (Object o)
{
if (o == null)
return false;
if (! (o instanceof Radio))
return false;
Radio other = (Radio) o;
return this.currentStation == other.currentStation;
}
public static void main(String[] args)
{
Radio amRadio = new AMRadio();
System.out.println(amRadio);
Radio fmRadio = new FMRadio();
System.out.println(fmRadio);
Radio xmRadio = new XMRadio();
System.out.println(xmRadio);
}
}
public class FMRadio extends Radio
{
private static final double Max_Station = 108.0;
private static final double Min_Station = 88.0;
private static final double Increment = .01;
public FMRadio()
{
currentStation = Min_Station;
}
public double getMax_Station()
{
return this.Max_Station;
}
public double getMin_Station()
{
return this.Min_Station;
}
public double getIncrement()
{
return this.Increment;
}
public String toString()
{
String message = ("FM " + this.currentStation);
return message;
}
}
答案 0 :(得分:2)
要点:(从帖子底部移动)
您需要了解测试ObjA == ObjB
,ObjA.equals(ObjB)
和ObjA instanceof ClassB
之间的区别。
此方法
public double getCurrentStation()
{
if (selectedRadio == radioAM)
{
return radioAM.getCurrentStaion();
}
else if (selectedRadio == radioFM)
{
return radioFM.getCurrentStaion();
}
return 0.0;
}
可能无法按预期工作。如果在Radio基类(你做过)中实现double getCurrentStation()
方法,你可以这样做:
public double getCurrentStation()
{
return selectedRadio.getCurrentStation();
}
但这可能有点过分,所以你应该用getCurrentStation()
替换AutoRadioSystem
中的selectedRadio.getCurrentStation()
来电。
同样,
public void selectRadio()
{
if (selectedRadio.equals(radioAM))
selectedRadio = radioFM;
}
无法按预期工作。你可能想要像
这样的东西public void selectRadio()
{
if (selectedRadio. instanceOf AMRadio))
selectedRadio = new FMRadio();
}
此外,
if (o == null)
return false;
if (! (o instanceof AutoRadioSystem))
return false;
可以简化为
if (! (o instanceof AutoRadioSystem))
return false;
如果o instanceof SomeClass
false
为o
,则null
会返回{{1}}。
还有其他问题。
答案 1 :(得分:1)
在equals
,AMRadio
等所有子类中定义FMRadio
方法。您可以使用Apache commons的EqualsBuilder
来实现此目的。 http://commons.apache.org/proper/commons-lang/apidocs/org/apache/commons/lang3/builder/EqualsBuilder.html
使用equals
的典型EqualsBuilder
方法如下所示。它使用反射来比较平等。
public boolean equals(Object obj) {
return EqualsBuilder.reflectionEquals(this, obj);
}
在比较时,不要使用==
,因为它会检查引用相等性,而不是逻辑相等性。使用{/ 1}}方法,如
equals