java 为什么这个 NumberFormatException？
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Why this NumberFormatException?
提问by Xavier Combelle
I have this stack trace (part of)
我有这个堆栈跟踪（部分）
Servlet.service() for servlet action threw exception
java.lang.NumberFormatException: For input string: "37648"
at java.lang.NumberFormatException.forInputString(NumberFormatException.java:48)
at java.lang.Long.parseLong(Long.java:403)
at java.lang.Long.valueOf(Long.java:482)
at java.lang.Long.decode(Long.java:593)
in one of my logfile I don't know what was real input string. But the user had made happen the same stack trace.
在我的一个日志文件中，我不知道什么是真正的输入字符串。但是用户已经发生了相同的堆栈跟踪。
How such a stacktrace can happen?
这样的堆栈跟踪是如何发生的？
回答by T.J. Crowder
Probably because they have a leading zero in their input.
可能是因为他们的输入中有一个前导零。
This runs fine:
这运行良好：
public class DecodeLong
{
public static final void main(String[] params)
{
long l;
l = Long.decode("37648");
System.out.println("l = " + l);
}
}
But if you change this:
但是如果你改变这个：
l = Long.decode("37648");
to this:
对此：
l = Long.decode("037648");
...it becomes invalid octal, and the exception from Long.parseLongdoesn't include the leading zero:
...它变成无效的八进制，并且 from 的异常Long.parseLong不包括前导零：
Exception in thread "main" java.lang.NumberFormatException: For input string: "37648"
at java.lang.NumberFormatException.forInputString(Unknown Source)
at java.lang.Long.parseLong(Unknown Source)
at java.lang.Long.valueOf(Unknown Source)
at java.lang.Long.decode(Unknown Source)
at DecodeLong.main(DecodeLong.java:24)
It doesn't include it because decodecalls parseLongwithout the zero, but with the base set to 8.
它不包括它，因为decode调用parseLong没有零，但基数设置为 8。
Talk about obscure. :-) So if you update your program to handle the exception by showing the actualinput, you'll probably find it's something along those lines.
谈论晦涩。:-) 因此，如果您通过显示实际输入来更新程序以处理异常，您可能会发现它与这些类似。
