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...)

  • 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 BufferedWriters 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