How to Resolve 'Stream Closed' Exception in Java IO

What causes a 'Stream Closed' Exception in Java IO, and how can it be resolved?

try (BufferedReader reader = new BufferedReader(new FileReader("file.txt"))) {
    String line;
    while ((line = reader.readLine()) != null) {
        // Process the line
    }
} catch (IOException e) {
    e.printStackTrace();
} // Stream is automatically closed here

The 'Stream Closed' IOException in Java occurs when an attempt is made to use an Input or Output stream that has already been closed. Addressing this issue requires understanding stream lifecycle and proper resource management in Java.

try (InputStream stream = new FileInputStream("example.txt")) {
    // Operations with the stream
} // Automatically closes the stream after try block ends.

Causes

• The stream has been closed explicitly using close() method in the code.
• The stream was closed due to reaching the end of the stream.
• Using the stream after it has been closed during a try-with-resources statement.

Solutions

• Ensure you are not attempting to read or write from a closed stream. Check the flow of your application to prevent accessing closed streams.
• Utilize the try-with-resources statement to automatically manage the stream lifecycle: it closes streams once they are no longer needed.
• Break down your code logic to ensure that streams remain open while needed and only close them after usage.

Mistake: Calling `close()` multiple times on the same stream object which can lead to confusion about the state of the stream.

Solution: Always check if a stream is already closed before calling close() again. Use a boolean flag if necessary.

Mistake: Ignoring the scope of the stream when using try-catch blocks, which can lead to premature closing.

Solution: Use try-with-resources to ensure that streams are only closed after all operations are complete.