- A File
object represents a file name, not an actual file. Such objects are,
moreover, immutable. Thus the code
File f1 = new File("foo");
File f2 = new File("bar");
f1.renameTo(f2);
will rename the file named "foo" (if it exists) to "bar".
It will not change the value of the File object referred to by
f1; in particular, the expression f1.getPath() will still
evaluate to "foo".
- The available
method of the
InputStream
class and its subclasses does not necessarily return the maximum number of
bytes that can be read without blocking. In particular, code of the form
int n = in.available();
byte buf = new byte[n];
in.read(buf);
is not guaranteed to read all of the remaining bytes from the given input
stream. Similarly, the ready
method of
Reader
and its subclasses may return false even if the stream is ready to
be read.
- The read(byte[])
and read(byte[], int, int)
methods of
InputStream
and its subclasses are not guaranteed to read all available bytes. A loop
may be required, for example, in order to read a large file into an array:
for (int off = 0; off < size;) {
int r = in.read(buf, off, buf.length - off);
if (r == -1) break;
off += r;
}
Alternatively, a
BufferedInputStream
may be used. Similar remarks apply to the
read(char[])
and
read(char[], int, int) methods of
Reader
and its subclasses.
- The
PrintStream
and
PrintWriter
classes suppress all I/O errors. To see whether an error has occurred,
invoke the checkError method.
-
PrintStream
and
PrintWriter
objects do not always flush their output. To arrange for automatic
flushing, use the two-argument constructors of these classes and specify
true for the second argument.