{"record":{"id":"641281d40f422898","repo":"apache/hadoop","slug":"can-t-find-class","errorCode":null,"errorMessage":"can't find class ","messagePattern":"can't find class ","errorType":"exception","errorClass":"IOException","httpStatus":null,"severity":"error","filePath":"hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapred/MapTask.java","lineNumber":738,"sourceCode":"            return partitions - 1;\n          }\n        };\n      }\n    }\n\n    @Override\n    public void write(K key, V value) throws IOException, InterruptedException {\n      collector.collect(key, value,\n                        partitioner.getPartition(key, value, partitions));\n    }\n\n    @Override\n    public void close(TaskAttemptContext context\n                      ) throws IOException,InterruptedException {\n      try {\n        collector.flush();\n      } catch (ClassNotFoundException cnf) {\n        throw new IOException(\"can't find class \", cnf);\n      }\n      collector.close();\n    }\n  }\n\n  @SuppressWarnings(\"unchecked\")\n  private <INKEY,INVALUE,OUTKEY,OUTVALUE>\n  void runNewMapper(final JobConf job,\n                    final TaskSplitIndex splitIndex,\n                    final TaskUmbilicalProtocol umbilical,\n                    TaskReporter reporter\n                    ) throws IOException, ClassNotFoundException,\n                             InterruptedException {\n    // make a task context so we can get the classes\n    org.apache.hadoop.mapreduce.TaskAttemptContext taskContext =\n      new org.apache.hadoop.mapreduce.task.TaskAttemptContextImpl(job, \n                                                                  getTaskID(),\n                                                                  reporter);","sourceCodeStart":720,"sourceCodeEnd":756,"githubUrl":"https://github.com/apache/hadoop/blob/2add9630210752f88ceb1bb74eb65e37bf41da8e/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapred/MapTask.java#L720-L756","documentation":"Error \"can't find class \" thrown in apache/hadoop.","triggerScenarios":"Thrown at hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapred/MapTask.java:738 when the library encounters an invalid state.","commonSituations":"See trigger scenarios.","solutions":["Ensure the class being deserialized is on the task classpath; ship required jars via distributed cache or libjars."],"exampleFix":null,"handlingStrategy":null,"validationCode":null,"typeGuard":null,"tryCatchPattern":null,"preventionTips":[],"tags":[],"backgroundTag":null,"analyzedSha":"2add9630210752f88ceb1bb74eb65e37bf41da8e","analyzedAt":"2026-08-22T19:55:07.957Z","schemaVersion":2},"datasetVersion":"2026-08-22T20:17:22.307Z"}