BufferedReader Pipeline

Reading a file line by line: the file on disk, the reader that opens it, the buffer that makes it efficient, and your readLine() loop.

FileReader

Opens the file and reads one character at a time. Works, but each character trip to the disk is slow.

BufferedReader

Wraps a FileReader. Pulls a block of characters into memory at once, then hands them to you line by line with readLine().

Your Loop

Keep calling readLine() until it returns null. That means end-of-file — stop reading and close().

Why the buffer? One big read from disk is much faster than many small ones. The BufferedReader fills its internal buffer in a single trip, then serves lines to your code from memory.

Pipeline

📄 poem.txt5 lines, ready

Disk

poem.txt

→

FileReader

char-by-char

BufferedReader

holds a buffer

→

Your code

readLine() loop

BufferedReader's buffer0 chars

Java code

Console output

$ java PoemReader
(click Run to start)

Status: idle

Tip: use Next step to walk through each readLine(), or press Auto-play to watch the loop run. Notice how readLine() returns null at end-of-file — that's what stops the loop.

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