当我尝试运行此代码时,它会一直返回错误的值,我无法弄清楚出错的地方。在我向catUp添加10之后它会正确打印出来,但是当我检查同一个值是否大于199时,由于某种原因,它会通过if语句。此外,当我在upCategory方法的末尾打印出来时,它给出了值1,但是当我在主要打印它时,它给我的值为3.
public void upCategory()
{
double catUp = radioXM.getCurrentStaion();
catUp += 10;
System.out.println(catUp);
if (catUp > 199.0);
{
catUp = 1;
radioXM.setCurrentStation(catUp);
System.out.println(catUp);
}
radioXM.setCurrentStation(catUp);
System.out.println(catUp);
}
public static void main (String [] args) {
AutoRadioSystem c = new AutoRadioSystem();
c.selectRadio();
double b = c.getCurrentStation();
System.out.println(b);
// this changes the radio to XM
c.selectRadio();
double d = c.getCurrentStation();
System.out.println(d);
//this is suppose to change the station up by 10 but gives incorrect value
c.upCategory();
double f = c.getCurrentStation();
System.out.println(f);
}
附带的附加代码......
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)
{
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 class XMRadio extends Radio
{
private static final double Max_Station = 199;
private static final double Min_Station = 1;
private static final double Increment = 1;
public XMRadio()
{
}
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 = ("XM "+ currentStation );
return message;
}
}
答案 0 :(得分:4)
这一行是问题所在:
if (catUp > 199.0);
Java将分号视为if
语句的主体,if
下面的括号中的块变为普通块,并且始终执行。
要将大括号中的块附加到if
语句,请删除分号:
if (catUp > 199.0)