Why Are Java NullPointerExceptions Missing StackTraces?

Failure to Capture StackTraces in Java NullPointerExceptions without Visible Errors

In some instances, Java code catches a NullPointerException but fails to log a StackTrace, leaving developers bewildered as only "java.lang.NullPointerException" is displayed.

This perplexing issue has left developers searching for solutions online to no avail. However, upon further investigation, it was discovered that the root cause lies in the HotSpot JVM's optimization strategies.

To counteract this optimization and restore StackTrace retrieval, developers must pass the following argument to the JVM:

-XX:-OmitStackTraceInFastThrow

This optimization stems from the JVM's handling of repetitive exceptions, such as NullPointerExceptions. On initial occurrence, the JVM logs the complete StackTrace. However, with frequent occurrences, the JVM suppresses StackTrace logging for both performance reasons and to avoid excessive log entries.

A detailed explanation of this implementation can be found in the HotSpot JVM source code, specifically within the "graphKit.cpp" file. By adjusting the OmitStackTraceInFastThrow variable, developers can regain stack trace visibility and facilitate debugging processes.

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