---

id: 57

slug: "reading-files"

title: "Reading files"

category: "io"

difficulty: "beginner"

jdkVersion: "11"

oldLabel: "Java 8"

modernLabel: "Java 11+"

oldApproach: "BufferedReader"

modernApproach: "Files.readString()"

oldCode: |-

StringBuilder sb = new StringBuilder();

try (BufferedReader br =

new BufferedReader(

new FileReader("data.txt"))) {

String line;

while ((line = br.readLine()) != null)

sb.append(line).append("\n");

}

String content = sb.toString();

modernCode: |-

String content =

Files.readString(Path.of("data.txt"));

summary: "Read an entire file into a String with one line."

explanation: "Files.readString() reads a file's entire content into a String. It handles\

\ encoding (UTF-8 by default) and resource cleanup. For large files, use Files.lines()\

\ for lazy streaming."

whyModernWins:

- icon: "📏"

title: "One line"

desc: "Replace 8 lines of BufferedReader boilerplate."

- icon: "🧹"

title: "Auto cleanup"

desc: "File handle is closed automatically."

- icon: "🌐"

title: "UTF-8 default"

desc: "Correct encoding by default — no charset confusion."

support:

state: "available"

description: "Widely available since JDK 11 (Sept 2018)"

prev: "io/io-class-console-io"

next: "io/writing-files"

related:

- "io/try-with-resources-effectively-final"

- "io/writing-files"

- "io/files-mismatch"

docs:

- title: "Files.readString()"

href: "https://docs.oracle.com/en/java/javase/25/docs/api/java.base/java/nio/file/Files.html#readString(java.nio.file.Path)"

- title: "Files.readAllLines()"

href: "https://docs.oracle.com/en/java/javase/25/docs/api/java.base/java/nio/file/Files.html#readAllLines(java.nio.file.Path)"