Files IO

REading

For small files use

byte[] bytes = Files.readAllBytes(Path.of(fileName));
String text = Files.readString(Path.of(fileName));
List<String> lines = Files.readAllLines(Path.of(fileName));
Stream<String> lines = Files.lines(Path.of(fileName));

LArge files

use nio
FileInputStream
we read a binary file byte by byte and then process these bytes

try (FileInputStream is = new FileInputStream(fileName)) {
  int b;
  while ((b = is.read()) != -1) { // -1 is EoF
    System.out.println("Byte: " + b);
  }
}

access is relatively expensive
large binary files with the NIO.2 InputStream

try (InputStream is = Files.newInputStream(Path.of(fileName))) {
  int b;
  while ((b = is.read()) != -1) {
    System.out.println("Byte: " + b);
  }
}

Reading faster with BufferedInputStream
- loads data from the operating system not byte by byte, but in blocks of 8 KB and stores them in memory. The bytes can then be read out again bit by bit – and from the main memory, which is much faster.
```
try (FileInputStream is = new FileInputStream(fileName);
   BufferedInputStream bis = new BufferedInputStream(is)) {
  int b;
  while ((b = bis.read()) != -1) {
    System.out.println("Byte: " + b);
  }
}
```
- The only exception is if you do not read data byte by byte, but in larger blocks whose size is adjusted to the block size of the file system.

Reading large text files with FileReader

When being loaded, an InputStreamReader can be used to convert their bytes into characters. Place it around a FileInputStream, and you can read characters instead of bytes

try (FileInputStream is = new FileInputStream(fileName);
   InputStreamReader reader = new InputStreamReader(is)) {
  int c;
  while ((c = reader.read()) != -1) {
    System.out.println("Char: " + (char) c);
  }
}

with FileReader: It combines FileInputStream and InputStreamReader,

try (FileReader reader = new FileReader(fileName)) {
  int c;
  while ((c = reader.read()) != -1) {
    System.out.println("Char: " + (char) c);
  }
}

Read text files faster with BufferedReader

improves upon InputStreamReader

try (FileReader reader = new FileReader(fileName);
   BufferedReader bufferedReader = new BufferedReader((reader))) {
  int c;
  while ((c = bufferedReader.read()) != -1) {
    System.out.println("Char: " + (char) c);
  }
}

try (FileReader reader = new FileReader(fileName);
   BufferedReader bufferedReader = new BufferedReader((reader))) {
  String line;
  while ((line = bufferedReader.readLine()) != null) {
    System.out.println("Line: " + line);
  }
}

BufferedReader achieves higher speeds by extending the InputStreamReader's 8 KB buffer with another buffer for 8,192 decoded characters.
it offers the additional method readLine(), which allows you to read and process the text file not only character by character but also line by line

Reading text files faster with the NIO.2 BufferedReader

try (BufferedReader reader = Files.newBufferedReader(Path.of(fileName))) {
  int c;
  while ((c = reader.read()) != -1) {
    System.out.println("Char: " + (char) c);
  }
}

JAva 8

https://reflectoring.io/processing-files-using-java-8-streams/

Streams and Buffers

Creating files

https://www.callicoder.com/how-to-create-new-file-java/

Paths

Locking

https://dzone.com/articles/locking-files-in-java
https://www.java67.com/2018/01/how-to-lock-file-before-writing-in-java.html

PDF

https://dzone.com/articles/pdf-creation-with-java

CSV

https://examples.javacodegeeks.com/core-java/java-convert-csv-excel-file-example/

REading

For small files use

LArge files

JAva 8

Streams and Buffers

Creating files

Paths

Locking

PDF

CSV

Links