我们的JUnit测试有时会因此堆栈跟踪而失败：
Caused by: java.lang.NullPointerException
at org.languagetool.rules.patterns.PatternRuleMatcher.formatMatches(PatternRuleMatcher.java:300)
at org.languagetool.rules.patterns.PatternRuleMatcher.createRuleMatch(PatternRuleMatcher.java:158)
[...]
第300行是：
if (j >= positions.size()) {
j是int，positions是List<Integer>，都是局部变量。这怎么会导致NullPointerException？我在代码中看不到任何地方
positions始终设置为null。它使用new ArrayList<>(tokens.length + 1)进行初始化。实际上，如果我在发生异常之前添加if (positions == null) { ... }一行，IntelliJ甚至会将positions == null标记为警告并告诉我将始终为假。
该软件使用线程，但由于这两个变量都是本地的，因此无关紧要。问题很少发生，我必须运行测试30-40次才能解决问题。
这里发生了什么，Java提供的线路可以关闭吗？ （我确定我正在查找正确的文件和正确的版本，文件也不会经常更改。）
这是Java 1.8.0_51。完整代码可以在https://github.com/languagetool-org/languagetool/blob/master/languagetool-core/src/main/java/org/languagetool/rules/patterns/PatternRuleMatcher.java#L300
看到更新：按要求完成堆栈跟踪：
testRules(org.languagetool.rules.ca.CatalanPatternRuleTest) Time elapsed: 29.978 sec <<< ERROR!
java.lang.RuntimeException: Error analyzing sentence: '<S> Va[anar/VAIP3S00,Va/_GV_] haver[haver/VAN00000,heure/VMN00000,haver/_GV_] una[un/DI0FS0,una/_GN_FS] reunió[reunió/NCFS000,reunió/_GN_FS].[</S>./_PUNCT]'
at org.languagetool.rules.patterns.PatternRule.match(PatternRule.java:191)
at org.languagetool.rules.patterns.PatternRuleTest.getMatches(PatternRuleTest.java:462)
at org.languagetool.rules.patterns.PatternRuleTest.testBadSentences(PatternRuleTest.java:294)
at org.languagetool.rules.patterns.PatternRuleTest.testGrammarRulesFromXML(PatternRuleTest.java:252)
at org.languagetool.rules.patterns.PatternRuleTest.runTestForLanguage(PatternRuleTest.java:187)
at org.languagetool.rules.patterns.PatternRuleTest.runGrammarRuleForLanguage(PatternRuleTest.java:103)
at org.languagetool.rules.patterns.PatternRuleTest.runGrammarRulesFromXmlTest(PatternRuleTest.java:91)
at org.languagetool.rules.ca.CatalanPatternRuleTest.testRules(CatalanPatternRuleTest.java:28)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at junit.framework.TestCase.runTest(TestCase.java:176)
at junit.framework.TestCase.runBare(TestCase.java:141)
at junit.framework.TestResult$1.protect(TestResult.java:122)
at junit.framework.TestResult.runProtected(TestResult.java:142)
at junit.framework.TestResult.run(TestResult.java:125)
at junit.framework.TestCase.run(TestCase.java:129)
at junit.framework.TestSuite.runTest(TestSuite.java:252)
at junit.framework.TestSuite.run(TestSuite.java:247)
at org.junit.internal.runners.JUnit38ClassRunner.run(JUnit38ClassRunner.java:86)
at org.apache.maven.surefire.junit4.JUnit4Provider.execute(JUnit4Provider.java:283)
at org.apache.maven.surefire.junit4.JUnit4Provider.executeWithRerun(JUnit4Provider.java:173)
at org.apache.maven.surefire.junit4.JUnit4Provider.executeTestSet(JUnit4Provider.java:153)
at org.apache.maven.surefire.junit4.JUnit4Provider.invoke(JUnit4Provider.java:128)
at org.apache.maven.surefire.booter.ForkedBooter.invokeProviderInSameClassLoader(ForkedBooter.java:203)
at org.apache.maven.surefire.booter.ForkedBooter.runSuitesInProcess(ForkedBooter.java:155)
at org.apache.maven.surefire.booter.ForkedBooter.main(ForkedBooter.java:103)
Caused by: java.lang.NullPointerException
at org.languagetool.rules.patterns.PatternRuleMatcher.formatMatches(PatternRuleMatcher.java:300)
at org.languagetool.rules.patterns.PatternRuleMatcher.createRuleMatch(PatternRuleMatcher.java:158)
at org.languagetool.rules.patterns.PatternRuleMatcher.match(PatternRuleMatcher.java:136)
at org.languagetool.rules.patterns.PatternRule.match(PatternRule.java:187)
... 27 more
答案 0 :(得分：4)
如果您完全确定用于构建库的源文件，则只能依赖堆栈跟踪中的行号。
在您的情况下，相关文件最近已更改。事实上，第300行的内容已经改变as seen by the diff：
故事的道德 - 除非您拥有原始来源，否则不要信任堆栈跟踪行号。
答案 1 :(得分：0)
Java 7没有出现这个问题，Java 1.8.0_60不再发生这种情况。所以这实际上是一个JVM错误，也许这个错误：http://bugs.java.com/view_bug.do?bug_id=8080156