英文:
Error when trying to use a custom exception in a static method
问题
我有一个名为Exercise08.java的Java类。在这个类中，我创建了一个内部类HexFormatException，它继承自NumberFormatException。
public class HexFormatException extends NumberFormatException {
public HexFormatException() {
super();
}
}
我还有一个静态方法hexToDecimal(String)，如果字符串不是十六进制，则应该抛出HexFormatException错误。
/**
* 将十六进制转换为十进制。
* @param hex 十六进制字符串
* @return 十六进制的十进制值
* @throws HexFormatException 如果hex不是十六进制
*/
public static int hexToDecimal(String hex) throws HexFormatException {
// 检查hex是否为十六进制，如果不是则抛出异常。
boolean patternMatch = Pattern.matches("[0-9A-F]+", hex);
if (!patternMatch)
throw new HexFormatException();
// 将hex转换为十进制
int decimalValue = 0;
for (int i = 0; i < hex.length(); i++) {
char hexChar = hex.charAt(i);
decimalValue = decimalValue * 16 + hexCharToDecimal(hexChar);
}
// 返回十进制值
return decimalValue;
}
但是，我得到了以下错误消息：
我对如何修复这个问题感到困惑。如果我抛出NumberFormatException，一切都能正常工作，但为什么对于我的自定义异常不起作用呢？
英文:
I have a java class called Exercise08.java. In this class I made the inner class HexFormatException which extends NumberFormatException.
public class HexFormatException extends NumberFormatException {
public HexFormatException() {
super();
}
}
I also have the static method hexToDecimal(String) which is supposed to throw a HexFormatException error if the String is not a hexadecimal.
/** Converts hexadecimal to decimal.
@param hex The hexadecimal
@return The decimal value of hex
@throws HexFormatException if hex is not a hexadecimal
*/
public static int hexToDecimal(String hex) throws HexFormatException {
// Check if hex is a hexadecimal. Throw Exception if not.
boolean patternMatch = Pattern.matches("[0-9A-F]+", hex);
if (!patternMatch)
throw new HexFormatException();
// Convert hex to a decimal
int decimalValue = 0;
for (int i = 0; i < hex.length(); i++) {
char hexChar = hex.charAt(i);
decimalValue = decimalValue * 16 + hexCharToDecimal(hexChar);
}
// Return the decimal
return decimalValue;
}
Instead I get this error message:
I'm really confused about how to fix this. Everything works fine if I throw a NumberFormatException, but why doesn't it work for my custom exception?
答案1
得分: 2
在静态方法中使用内部类，该内部类也必须是静态的。 <br>
public static class HexFormatException extends NumberFormatException {
public HexFormatException() {
super();
}
}
英文:
To use inner class in static method it must be static too. <br>
public static class HexFormatException extends NumberFormatException {
public HexFormatException() {
super();
}
}
答案2
得分: 1
你已将HexFormatException定义为内部类，这意味着它属于包含它的实例。在静态方法中，没有默认的包含实例，所以会出现这个错误。
一个简单的解决方法是使用static关键字声明该类：
public static class HexFormatException ...
英文:
You've made HexFormatException an inner class which means it belongs to an enclosing instance. In at static method there is no default enclosing instance so you get this error.
A simple fix is to declare the class with static:
public static class HexFormatException ...
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