在让这个项目正常工作方面我遇到了很多问题,但我目前一直致力于让这个类(class)正常工作。它应该做的就是从 radio 类中获取当前电台并将其传递给此类。问题是我试图在 AM 和 FM 之间进行选择,但每次运行它时,它只显示 AM 电台。我不明白为什么它会自动设置到该电台。
public class AutoRadioSystem
{
private Radio selectedRadio;
private AMRadio radioAM;
private FMRadio radioFM;
private XMRadio radioXM;
//is this the correct place to initialize these?
Radio amRadio = new AMRadio();
Radio fmRadio = new FMRadio();
public AutoRadioSystem()
{
//even making the selected radio FM still produces values for AM
selectedRadio = radioFM;
}
// this is where my problem currently lies and probably much more. Shouldn't it return 0.0 without any station being selected.
public double getCurrentStation()
{
if (selectedRadio == radioAM)
{
return amRadio.getCurrentStaion();
}
else if (selectedRadio == radioFM)
{
return fmRadio.getCurrentStaion();
}
return 0.0;
}
//I'm not sure if i'm setting this up correctly to switch the radio from am to fm
public void selectRadio()
{
if (selectedRadio == radioAM)
selectedRadio = radioFM;
}
public static void main (String [] args) {
AutoRadioSystem c = new AutoRadioSystem();
c.selectRadio();
double b = c.getCurrentStation();
System.out.println(b);
}
}
public class AMRadio extends Radio
{
private static final double Max_Station = 1605;
private static final double Min_Station = 535;
private static final double Increment = 10;
public AMRadio()
{
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 = ("AM " + this.currentStation);
return message;
}
}
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;
}
}
public abstract class Radio
{
double currentStation;
RadioSelectionBar radioSelectionBar;
public Radio()
{
}
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;
}
}
最佳答案
问题是,在 .getCurrentStation() 中,selectedRadio 和 radioAM 都不是 init 并且为 null。
错误开头为:
public void selectRadio()
{
if (selectedRadio == radioAM)
{
selectedRadio = radioFM;
}
}
这里,selectedRadio = null,所以它永远不会被赋值。
编辑:我相信您才刚刚开始,所以更多细节会有所帮助。
- 声明两个字段 amRadio 和 radioAM 然后初始化其中一个并使用另一个时会犯错误。
- 您没有为 selectedRadio 设置值并进行比较,这总是返回 false
- 实例初始化值的最佳位置是构造函数方法,这里是 AutoRadioSystem()
您可能想将代码更改为如下所示:
private Radio selectedRadio;
public AutoRadioSystem()
{
selectedRadio = new FMRadio();
}
// To compare, using instanceOf, but better design will use enum value instead, up to you
关于java - java赋值中可能存在逻辑错误的误解,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/18988984/