To get the stack traces back, you need to pass the option -XX:-OmitStackTraceInFastThrow to the JVM.
The optimization is that when an exception (typically a NullPointerException) occurs for the first time, the full stack trace is printed and the JVM remembers the stack trace (or maybe just the location of the code). When that exception occurs often enough, the stack trace is not printed anymore, both to achieve better performance and not to flood the log with identical stack traces.
Creating BufferedReader from Files.newBufferedReader
Files.newBufferedReader(Paths.get("a.txt"), StandardCharsets.UTF_8);
when running the application it may throw the following exception:
java.nio.charset.MalformedInputException: Input length = 1
But
new BufferedReader(new InputStreamReader(new FileInputStream("a.txt"),"utf-8"));
works well.
The different is that, the former uses CharsetDecoder default action.
The default action for malformed-input and unmappable-character errors is to report them.
while the latter uses the REPLACE action.
cs.newDecoder().onMalformedInput(CodingErrorAction.REPLACE).onUnmappableCharacter(CodingErrorAction.REPLACE)