BufferedWriterpublic class BufferedWriter extends Writer | Write 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. |
| Fields Summary |
|---|
| private Writer | out | | private char[] | cb | | private int | nChars | | private int | nextChar | | private static int | defaultCharBufferSize | | private String | lineSeparatorLine separator string. This is the value of the line.separator
property at the moment that the stream was created. |
| Constructors Summary |
|---|
public BufferedWriter(Writer out)Create a buffered character-output stream that uses a default-sized
output buffer.
this(out, defaultCharBufferSize);
| public BufferedWriter(Writer out, int sz)Create a new buffered character-output stream that uses an output
buffer of the given size.
super(out);
if (sz <= 0)
throw new IllegalArgumentException("Buffer size <= 0");
this.out = out;
cb = new char[sz];
nChars = sz;
nextChar = 0;
lineSeparator = (String) java.security.AccessController.doPrivileged(
new sun.security.action.GetPropertyAction("line.separator"));
|
| Methods Summary |
|---|
| public void | close()Close the stream.
synchronized (lock) {
if (out == null)
return;
flushBuffer();
out.close();
out = null;
cb = null;
}
| | private void | ensureOpen()Check to make sure that the stream has not been closed
if (out == null)
throw new IOException("Stream closed");
| | public void | flush()Flush the stream.
synchronized (lock) {
flushBuffer();
out.flush();
}
| | void | flushBuffer()Flush the output buffer to the underlying character stream, without
flushing the stream itself. This method is non-private only so that it
may be invoked by PrintStream.
synchronized (lock) {
ensureOpen();
if (nextChar == 0)
return;
out.write(cb, 0, nextChar);
nextChar = 0;
}
| | private int | min(int a, int b)Our own little min method, to avoid loading java.lang.Math if we've run
out of file descriptors and we're trying to print a stack trace.
if (a < b) return a;
return b;
| | public void | newLine()Write a line separator. The line separator string is defined by the
system property line.separator, and is not necessarily a single
newline ('\n') character.
write(lineSeparator);
| | public void | write(int c)Write a single character.
synchronized (lock) {
ensureOpen();
if (nextChar >= nChars)
flushBuffer();
cb[nextChar++] = (char) c;
}
| | public void | write(char[] cbuf, int off, int len)Write 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.
synchronized (lock) {
ensureOpen();
if ((off < 0) || (off > cbuf.length) || (len < 0) ||
((off + len) > cbuf.length) || ((off + len) < 0)) {
throw new IndexOutOfBoundsException();
} else if (len == 0) {
return;
}
if (len >= nChars) {
/* If the request length exceeds the size of the output buffer,
flush the buffer and then write the data directly. In this
way buffered streams will cascade harmlessly. */
flushBuffer();
out.write(cbuf, off, len);
return;
}
int b = off, t = off + len;
while (b < t) {
int d = min(nChars - nextChar, t - b);
System.arraycopy(cbuf, b, cb, nextChar, d);
b += d;
nextChar += d;
if (nextChar >= nChars)
flushBuffer();
}
}
| | public void | write(java.lang.String s, int off, int len)Write a portion of a String.
If the value of the len parameter is negative then no
characters are written. This is contrary to the specification of this
method in the {@linkplain java.io.Writer#write(java.lang.String,int,int)
superclass}, which requires that an {@link IndexOutOfBoundsException} be
thrown.
synchronized (lock) {
ensureOpen();
int b = off, t = off + len;
while (b < t) {
int d = min(nChars - nextChar, t - b);
s.getChars(b, b + d, cb, nextChar);
b += d;
nextChar += d;
if (nextChar >= nChars)
flushBuffer();
}
}
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