Module java.base
Package java.io

# Class BufferedWriter

java.lang.Object
java.io.Writer
java.io.BufferedWriter

All Implemented Interfaces:
  `Closeable`, `Flushable`, `Appendable`, `AutoCloseable`

public class BufferedWriter extends Writer
Writes text to a character-output stream, buffering characters so as to provide for the efficient writing of single characters, arrays, and strings.

The buffer size may be specified, or the default size may be accepted. The default is large enough for most purposes.

A newLine() method is provided, which uses the platform's own notion of line separator as defined by the system property `line.separator`. Not all platforms use the newline character ('\n') to terminate lines. Calling this method to terminate each output line is therefore preferred to writing a newline character directly.

In general, a Writer sends its output immediately to the underlying character or byte stream. Unless prompt output is required, it is advisable to wrap a BufferedWriter around any Writer whose write() operations may be costly, such as FileWriters and OutputStreamWriters. For example,

     PrintWriter out
       = new PrintWriter(new BufferedWriter(new FileWriter("foo.out")));

will buffer the PrintWriter's output to the file. Without buffering, each invocation of a print() method would cause characters to be converted into bytes that would then be written immediately to the file, which can be very inefficient.

Since:
  1.1
See Also:
  - `PrintWriter`
  - `FileWriter`
  - `OutputStreamWriter`
  - `Files.newBufferedWriter(java.nio.file.Path, java.nio.charset.Charset, java.nio.file.OpenOption...)`

- ## Field Summary

  ### Fields declared in class java.io.Writer

  `lock`

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `BufferedWriter(Writer out)`
  Creates a buffered character-output stream that uses a default-sized output buffer.
  `BufferedWriter(Writer out, int sz)`
  Creates a new buffered character-output stream that uses an output buffer of the given size.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `void`
  `close()`
  Closes the stream, flushing it first.
  `void`
  `flush()`
  Flushes the stream.
  `void`
  `newLine()`
  Writes a line separator.
  `void`
  `write(char[] cbuf, int off, int len)`
  Writes a portion of an array of characters.
  `void`
  `write(int c)`
  Writes a single character.
  `void`
  `write(String s, int off, int len)`
  Writes a portion of a String.

  ### Methods declared in class java.io.Writer

  `append, append, append, nullWriter, write, write`

  ### Methods declared in class java.lang.Object

  `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- ## Constructor Details

  - ### BufferedWriter

    public BufferedWriter(Writer out)
    Creates a buffered character-output stream that uses a default-sized output buffer.
    Parameters:
      `out` - A Writer

  - ### BufferedWriter

    public BufferedWriter(Writer out, int sz)
    Creates a new buffered character-output stream that uses an output buffer of the given size.
    Parameters:
      `out` - A Writer
      `sz` - Output-buffer size, a positive integer
    Throws:
      `IllegalArgumentException` - If `sz <= 0`

- ## Method Details

  - ### write

    public void write(int c) throws IOException
    Writes a single character.
    Overrides:
      `write` in class `Writer`
    Parameters:
      `c` - int specifying a character to be written
    Throws:
      `IOException` - If an I/O error occurs

  - ### write

    public void write(char[] cbuf, int off, int len) throws IOException
    Writes a portion of an array of characters.

    Ordinarily this method stores characters from the given array into this stream's buffer, flushing the buffer to the underlying stream as needed. If the requested length is at least as large as the buffer, however, then this method will flush the buffer and write the characters directly to the underlying stream. Thus redundant `BufferedWriter`s will not copy data unnecessarily.

    Specified by:
      `write` in class `Writer`
    Parameters:
      `cbuf` - A character array
      `off` - Offset from which to start reading characters
      `len` - Number of characters to write
    Throws:
      `IndexOutOfBoundsException` - If `off` is negative, or `len` is negative, or `off + len` is negative or greater than the length of the given array
      `IOException` - If an I/O error occurs

  - ### write

    public void write(String s, int off, int len) throws IOException
    Writes a portion of a String.
    Overrides:
      `write` in class `Writer`
    Implementation Requirements:
      While the specification of this method in the superclass recommends that an `IndexOutOfBoundsException` be thrown if `len` is negative or `off + len` is negative, the implementation in this class does not throw such an exception in these cases but instead simply writes no characters.
    Parameters:
      `s` - String to be written
      `off` - Offset from which to start reading characters
      `len` - Number of characters to be written
    Throws:
      `IndexOutOfBoundsException` - If `off` is negative, or `off + len` is greater than the length of the given string
      `IOException` - If an I/O error occurs

  - ### newLine

    public void newLine() throws IOException
    Writes a line separator. The line separator string is defined by the system property `line.separator`, and is not necessarily a single newline ('\n') character.
    Throws:
      `IOException` - If an I/O error occurs

  - ### flush

    public void flush() throws IOException
    Flushes the stream.
    Specified by:
      `flush` in interface `Flushable`
    Specified by:
      `flush` in class `Writer`
    Throws:
      `IOException` - If an I/O error occurs

  - ### close

    public void close() throws IOException
    Description copied from class: `Writer`
    Closes the stream, flushing it first. Once the stream has been closed, further write() or flush() invocations will cause an IOException to be thrown. Closing a previously closed stream has no effect.
    Specified by:
      `close` in interface `AutoCloseable`
    Specified by:
      `close` in interface `Closeable`
    Specified by:
      `close` in class `Writer`
    Throws:
      `IOException` - If an I/O error occurs