Java Solutions: Writer

Tuesday, May 6, 2014

Read from and write to a file in Java (2): other commonly used methods

The most commonly handy methods for reading from and writing to a file are in the java.nio.file.Files class, which was introduced in Java 7. The following methods had been mostly used before the Files class was introduced.

A. Read from a file

File theFile = new File("<directory>/<file name>");

1. The Scanner
Scanner scanner = new Scanner(theFile);
while (scanner.hasNextLine()) {
System.out.println(scanner.nextLine());
}

2. The BufferedReader and FileReader
BufferedReader theReader = new BufferedReader(
new FileReader(theFile));
String line = "";
while ((line = theReader.readLine()) != null) {
System.out.println(line);
}

3. The InputStreamReader and FileInputStream
CharSet cs = CharSet.forName(System.getProperty("file.encoding"));
InputStreamReader theReaer = new InputStreamReader(
new FileInputStream(theFile), cs);
int char = -1;
while ((char = theReader.read()) != -1) {
System.out.println(char);
}

4. The BufferedInputStream and FileInputStream
BufferedInputStream bis = new BufferedInputStream(
new FileInputStream(theFile));
byte[] theBytes = new byte[theFile.length()];
bis.read(theBytes, 0, theBytes.length);

B. Write to a file

File theFile = new File("<directory>/<file name>");

1. The PrintWriter, BufferedWriter, and FileWriter
PrintWriter pw = new PrintWriter(
new BufferedReader(
new FileWriter(theFiel, true)));
pw.println("The word to write");

2. The OutputStreamWriter and the FileOutputStream
OutputStreamWriter osw = new OutputStreamWriter(
new FileOutputStream(theFile, true));
String theString = "The word to write";
osw.write(theString, 0, theString.length());

3. The BufferedOutputStream and the FileOutputStream
BufferedOutputStream bos = new BufferedOutputStream(
new FileOutputStream(theFile, true));
byte[] theBytes = (new String("The word to write")).getBytes();
bos.write(theBytes, 0, theBytes.length);

Previous <

References:

1. Read from and write to a file in Java (1): java.nio.file.Files
2. Read from and write to the command line in Java
3. Java communications over network
4. Reading, Writing, and Creating Files
5. Java IO Tutorial

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Monday, May 5, 2014

Read from and write to a file in java (1): java.nio.file.Files

The Files class was introduced in Java 7. It contains only static methods that are convenient to use for operations on a file.

A. Read from a file

Path theFile = FileSystems.getDefault().getPath("<dirctory>", "<file name>");

1. the readAllLines method
List<String> allLines = Files.readAllLines(theFile);

2. the newBufferedReader
BufferedReader reader = Files.newBufferedReader(theFile);
String line = "";
for ((line = reader.readLine()) != null) {
System.out.println(line);
}

3. the lines method
Stream<String> lineStream = Files.lines(theFile);
List<String> lineList = lineStream.collect(Collectors.toList());

4. the readAllBytes method
byte[] allByes = Files.readAllBytes(theFile);

5. the newInputStream method
InputStream is = Files.newInputStream(theFile);
byte[] isBytes = new byte[Files.size(theFile)];
is.read(isBytes); //read the file to the byte array

6. the newByteChannel method
//The advantage of using SeekableByteChannel is that it allows you
//to set an arbitrary position to start reading and writing
SeekableByteChannel sbc = Files.newByteChannel(theFile);
String encode = System.getProperty("file.encoding");
ByteBuffer theBuffer = ByteBuffer.allocate(theFile.toFile().length());
sbc.read(theBuffer);
theBuffer.reWind();
String theString = CharSet.forName(encode).decode(theBuffer).toString();

B. Write to a file

Path theFile = FileSystems.getDefault().getPath("<dirctory>", "<file name>");

1. the newBufferedWriter method
BufferedWriter writer = Files.newBufferedWriter(theFile);
PrintWriter pw = new PrintWriter(writer);

2. the newOutputStream method
OutputStream os = Files.newOutputStream(theFile);

3. the write method
byte[] theBytes = (new String("The words to write")).getBytes();
Files.write(theFile, theBytes);

4. the newByteChannel method
SeekableByteChannel sbc = Files.newByteChannel(theFile);
byte[] theBytes = (new String("The words to write")).getBytes();
ByteBuffer theBuffer = ByteBuffer.wrap(theBytes);
sbc.write(theBuffer);

> Next

References:

1. Read from and write to a file in Java (2): Other commonly used methods
2. Read from and write to the command line in Java
3. Java communications over network
4. Class Files

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