Summary - I/O and NIO basics

Combine Path, Files and readString to write a file scanner.

Summary - I/O and NIO basics

In this group you saw the core NIO.2 tools: paths with Path, file operations with Files, easy text with readString/writeString, buffered reading with BufferedReader, and NIO channels with FileChannel. These tools are the foundation of file handling in Java.

Now you will combine these into a mini task: building a small notebook structure.

Exercise Notebook: write and read

Write main in a Notebook class; create a temp file with Files.createTempFile("n", ".txt"). Write with Files.writeString(p, "Note 1"). Read with String s = Files.readString(p). Print with System.out.println(s).

Show example solution

import java.nio.file.*;

class Notebook {
    public static void main(String[] args) throws Exception {
        Path p = Files.createTempFile("n", ".txt");
        Files.writeString(p, "Note 1");
        String s = Files.readString(p);
        System.out.println(s);
    }
}

Exercise Read a line with BufferedReader

Write main in a new LineDemo class; create a temp file with Files.createTempFile("l", ".txt"), write Files.writeString(p, "Line 1"). In a try (BufferedReader r = Files.newBufferedReader(p)) block, call r.readLine() and print it.

Show example solution

import java.nio.file.*;
import java.io.*;

class LineDemo {
    public static void main(String[] args) throws Exception {
        Path p = Files.createTempFile("l", ".txt");
        Files.writeString(p, "Line 1");
        try (BufferedReader r = Files.newBufferedReader(p)) {
            System.out.println(r.readLine());
        }
    }
}

Test yourself

What is the best method to read a small text in one go?
- FileChannel
- Files.readString
- InputStream.read
- BufferedReader.readLine
Show answer

Files.readString — Files.readString is ideal for small texts.
Match the I/O summary

Path

Represents a path
Files

File operations
readString

Reads text
FileChannel

NIO channel

Next lesson: Project design

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