Why is My Java BufferedWriter Truncating Output to My SQL File?

BufferedWriter Text Truncation in Output File

This Java program transforms CSV data into SQL commands for data insertion into a table. However, it encounters an issue where not all the transformed text appears in the output SQL file.

The source file contains over 10,000 lines of data, and the program seemingly functions correctly, but it abruptly stops midway through generating an SQL statement. This truncation typically occurs after processing approximately 10,000 lines, leaving several hundred lines unread.

To resolve this issue, it is necessary to close the OutputStream to ensure that any remaining data is written to the file:

out.close();

Understanding Output Buffers in Java

A BufferedWriter internally maintains a buffer that stores written data temporarily. The default buffer size is 8192 characters, which can accommodate hundreds of lines of text. When the buffer reaches capacity or when the stream is closed, the data is flushed to the underlying file.

In this case, the buffer size is sufficient to hold all the lines of data being processed. However, until the buffer is flushed, the data is not actually written to the file. Closing the OutputStream explicitly triggers the flushing process, ensuring that all the transformed text is written to the SQL file.

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