BufferedWriter和newLine

BufferedWriter類的newLine方法

源碼:
 /**
     * Writes a line separator.  The line separator string is defined by the
     * system property <tt>line.separator</tt>, and is not necessarily a single
     * newline ('/n') character.
     *
     * @exception  IOException  If an I/O error occurs
     */
    public void newLine() throws IOException {
 write(lineSeparator);
    }
 
  BufferedWriter類的概述
 /**
 * Writes text to a character-output stream, buffering characters so as to
 * provide for the efficient writing of single characters, arrays, and strings.
 *
 * <p> The buffer size may be specified, or the default size may be accepted.
 * The default is large enough for most purposes.
 *
 * <p> A newLine() method is provided, which uses the platform's own notion of
 * line separator as defined by the system property <tt>line.separator</tt>.
 * 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.
 *
 * <p> 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,
 *
 * <pre>
 * PrintWriter out
 *   = new PrintWriter(new BufferedWriter(new FileWriter("foo.out")));
 * </pre>
 *
 * 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.
 *
 * @see PrintWriter
 * @see FileWriter
 * @see OutputStreamWriter
 *
 * @version  1.29, 05/11/30
 * @author Mark Reinhold
 * @since JDK1.1
 */
 
public class BufferedWriterextends Writer將文本寫入字元輸出資料流，緩衝各個字元，從而提供單個字元、數組和字串的高效寫入。

可以指定緩衝區的大小，或者接受預設的大小。在大多數情況下，預設值就足夠大了。

該類提供了 newLine() 方法，它使用平台自己的行分隔字元概念，此概念由系統屬性 line.separator 定義。並非所有平台都使用新行符 ('/n') 來終止各行。因此調用此方法來終止每個輸出行要優於直接寫入新行符。

通常 Writer 將其輸出立即發送到底層字元或位元組流。除非要求提示輸出，否則建議用 BufferedWriter 封裝所有其 write() 操作可能開銷很高的 Writer（如 FileWriters 和 OutputStreamWriters）。例如，

 PrintWriter out  = new PrintWriter(new BufferedWriter(new FileWriter("foo.out")));
 將緩衝 PrintWriter 對檔案的輸出。如果沒有緩衝，則每次調用 print() 方法會導致將字元轉換為位元組，然後立即寫入到檔案，而這是極其低效的。