Files, I/O & Robust Error Handling

What you will be able to do

• Create, read, copy, move and delete files and folders with java.nio.file
• Read and write text and binary data with the right reader, writer or stream
• Close every resource safely with try-with-resources, including your own classes
• Process CSV and other text formats and handle bad lines without crashing
• Design exceptions and error messages that a real application can rely on

What it will cover

1. 9.1Exceptions in Depth

   Go past try and catch: the full exception hierarchy, chaining causes and reading complex stack traces.

   Show 5 topics
   • Throwable, Error and Exception: what to catch and what not to
   • Exception chaining with a cause
   • Reading stack traces with 'Caused by' sections
   • Rethrowing and wrapping checked exceptions
   • Cost of exceptions and why not to use them for normal flow

2. 9.2try-with-resources in Depth

   Close files and other resources correctly every time, even when things fail.

   Show 5 topics
   • AutoCloseable and Closeable
   • Several resources and the order they close
   • Suppressed exceptions and getSuppressed()
   • Writing your own AutoCloseable class
   • Replacing old finally-close code

3. 9.3Paths & Files

   Work with file paths and folders using Path and the Files class.

   Show 5 topics
   • Path.of, relative and absolute paths, resolve and normalize
   • Checking, creating and deleting files and folders
   • Copying and moving with options
   • Listing and walking folders
   • Paths that work on Windows, macOS and Linux

4. 9.4Reading & Writing Text Files

   Read and write text files, small and large, with the right method for each.

   Show 5 topics
   • Files.readString, readAllLines and writeString
   • Files.lines for large files
   • BufferedReader and BufferedWriter
   • Character sets and why to use UTF-8
   • Appending versus overwriting

5. 9.5Byte & Character Streams

   The classic java.io stream classes and how bytes and characters differ.

   Show 6 topics
   • InputStream and OutputStream for bytes
   • Reader and Writer for characters
   • Buffering and why it matters
   • Bridging with InputStreamReader and OutputStreamWriter
   • Copying binary files such as images
   • PrintWriter for formatted output

6. 9.6CSV & Structured Text

   Turn text files into objects and back, and deal with messy real data.

   Show 6 topics
   • Parsing CSV lines into records
   • Quoted fields and commas inside values
   • Skipping and reporting bad rows
   • Writing reports and CSV output
   • Properties files for settings
   • Writing simple JSON text by hand and why libraries are used later

7. 9.7Serialization Basics

   Save objects as bytes with Java serialization and learn why it is rarely the first choice today.

   Show 5 topics
   • Serializable, ObjectOutputStream and ObjectInputStream
   • transient fields
   • serialVersionUID and class changes
   • Security risks of reading untrusted data
   • Text formats as the usual alternative

8. 9.8Designing Error Handling

   Decide what to throw, where to catch and what to tell the user, so errors are clear and nothing is silently lost.

   Show 6 topics
   • Checked or unchecked for your own exceptions
   • Validating early and failing fast
   • Translating low-level exceptions at layer boundaries
   • Messages for users versus details for developers
   • Logging errors with java.util.logging
   • Retrying and recovering from file errors

9. 9.9Files & I/O Mini Projects

   Small programs that read, process and write real files with careful error handling.

   Show 4 topics
   • Expense tracker that saves to CSV
   • Log file analyzer with a summary report
   • Folder organiser that sorts files by type
   • Student records import with error reporting