Java 11: use `Files.readString` to read a file to a String

[yeikel]

There are many patterns to read all the contents of a File to a String

All the methods below will throw OOM if the file is larger than the available memory

// Java 7

String content = new String(Files.readAllBytes(Paths.get("file.txt")), StandardCharsets.UTF_8)`

// Using Guava 
import com.google.common.base.Charsets;
import com.google.common.io.Files;

String text = Files.toString(new File(path), Charsets.UTF_8);

// Using Files.readAllBytes

Path filePath = Path.of("file.txt");
String fileContent = "";

try
{
    byte[] bytes = Files.readAllBytes(Paths.get(filePath));
    fileContent = new String (bytes);
} 
catch (IOException e) 
{
    e.printStackTrace();
}

// Using BufferedReader (Java 6)

Path filePath = Path.of("file.txt");
String fileContent = "";

StringBuilder contentBuilder = new StringBuilder();
try (BufferedReader br = new BufferedReader(new FileReader(filePath))) 
{

    String sCurrentLine;
    while ((sCurrentLine = br.readLine()) != null) 
    {
        contentBuilder.append(sCurrentLine).append("\n");
    }
} 
catch (IOException e) 
{
    e.printStackTrace();
}

fileContent = contentBuilder.toString();

// Using Commons IO

File file = new File("file.txt");

String content = FileUtils.readFileToString(file, "UTF-8");

// Using the Scanner class

  File file = new File("file.txt");
  StringBuilder fileContents = new StringBuilder();        

    try (Scanner scanner = new Scanner(file)) {
        while(scanner.hasNextLine()) {
            fileContents.append(scanner.nextLine() + System.lineSeparator());
        }

    }

// Using the Scanner class with String concatenation

  File file = new File("file.txt");
  String fileContents = ""  

    try (Scanner scanner = new Scanner(file)) {
        while(scanner.hasNextLine()) {
            fileContents = fileContents  + System.lineSeparator());
        }
     
    }

Starting with Java 11, all the patterns above could be replaced with

Path filePath = Path.of("file.txt");
String content = Files.readString(fileName);