Databases
StackOverflow2013
Postsdbo
PO(Unknown Source) in Exception stack trace
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO(Unknown Source) in Exception stack trace
    primarykey
    data
    text
    <h3>Background</h3> <blockquote> <p><em>This question is related to</em> <a href="https://stackoverflow.com/questions/3131865/why-does-string-valueofnull-throw-a-nullpointerexception">Why does String.valueOf(null) throw a NullPointerException?</a></p> </blockquote> <p>Consider the following snippet:</p> <pre><code>public class StringValueOfNull { public static void main(String[] args) { String.valueOf(null); // programmer intention is to invoke valueOf(Object), but instead // code invokes valueOf(char[]) and throws NullPointerException } } </code></pre> <p>As explained in the answer to the linked question, Java's method overloading resolves the above invokation to <a href="http://java.sun.com/javase/6/docs/api/java/lang/String.html#valueOf%28char%5B%5D%29" rel="noreferrer"><code>String.valueOf(char[])</code></a>, which rightfully results in a <code>NullPointerException</code> at run-time.</p> <p>Compiled in Eclipse and <code>javac 1.6.0_17</code>, this is the stack trace:</p> <pre><code>Exception in thread "main" java.lang.NullPointerException at java.lang.String.&lt;init&gt;(Unknown Source) at java.lang.String.valueOf(Unknown Source) at StringValueOfNull.main(StringValueOfNull.java:3) </code></pre> <p>Note that the stack trace above is missing the <em>KEY</em> information: it does <em>NOT</em> have the full signature of the <code>valueOf</code> method! It just says <code>String.valueOf(Unknown Source)</code>!</p> <p>In most situations I've encountered, exception stack traces always have the complete signature of the methods that are actually in the stack trace, which of course is <em>very helpful</em> in identifying the problem immediately and a major reason why the stack trace (which needless to say is rather expensive to construct) is provided in the first place.</p> <p>And yet, in this case, the stack trace <em>does not help at all</em>. It has failed miserably in helping the programmer identify the problem.</p> <p>As is, I can see 3 ways that a programmer can identify the problem with the above snippet:</p> <ul> <li>Programmer realizes on his/her own that the method is overloaded, and by resolution rule, the "wrong" overload gets invoked in this case</li> <li>Programmer uses a good IDE that allows him/her to quickly see which method is selected <ul> <li>In Eclipse, for example, mouse-hovering on the above expression quickly tells programmer that the <code>String valueOf(char[] data)</code> is indeed the one selected</li> </ul></li> <li>Programmer examines the bytecode (ugh!)</li> </ul> <p>The last option is probably the least accessible, but of course is the Ultimate Answer (a programmer may misunderstood the overloading rule, IDE may be buggy, but bytecodes always(?) tell the truth on what's being done).</p> <hr> <h3>The questions</h3> <ul> <li>Why is the stack trace so uninformative in this case with regards to the signatures of the methods that are actually in the stack trace? <ul> <li>Is this due to the compiler? The runtime? Something else?</li> </ul></li> <li>In what other (rare?) scenarios can the stack trace fail to capture essential information like these?</li> </ul>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USCommunity
    1. USpolygenelubricants
    plurals
    1. PL
      singulars
      1. LTLinked
    1. PL
      singulars
      1. LTLinked
    2. PL
      singulars
      1. LTLinked
    3. PL
      singulars
      1. LTDuplicate
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    3. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. PO(Unknown Source) in Exception stack trace
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO(Unknown Source) in Exception stack trace
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. PO(Unknown Source) in Exception stack trace
      1. This table or related slice is empty.
      1. VTUpMod
    1. CONote that the exact content of a stack trace is not specified in the JVM spec or the JLS, so implementors are pretty free on what they provide. Also: my installation provides the source file and line numbers in the stacktrace (it's the OpenJDK, however), so I think it depends on what you use to run your code (JRE vs. JDK).
      singulars
      1. PO(Unknown Source) in Exception stack trace
      1. USJoachim Sauer
    2. COWhoa I just realized that I may have made a fool out of myself here; exception stack traces NEVER includes the signature of the method, apparently(?). It includes only filename and line number at best. I swear I've seen signatures too before, but maybe I was mistaken somehow. Would've been nice, though (and should be easy to implement too, since information about signature is more available than source file name and line number).
      singulars
      1. PO(Unknown Source) in Exception stack trace
      1. USpolygenelubricants
    3. COincluding full method signatures would make stack traces really hard to read.
      singulars
      1. PO(Unknown Source) in Exception stack trace
      1. USunbeli
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload