/** {@inheritDoc} */
public float readFloat() throws IOException {
fileSize -= 4;
if (fileSize < 0) {
throw new EOFException();
}
return dataInput.readFloat();
}
public boolean hasNext() {
if (raf == null || !raf.getChannel().isOpen()) return false;
if (flagNext == true) return true; // Déjà lue
flagNext = true;
try {
next = new Entry();
next.timestamp = (long) raf.readInt();
next.value = raf.readFloat();
if (this.end != null && next.timestamp > this.end) {
next = null;
close();
return false;
}
return true;
} catch (IOException e) {
// EOF ou autre erreur d'IO
if (!(e instanceof EOFException)) logger.log(Level.WARNING, e.getMessage(), e);
next = null;
try {
close();
} catch (IOException e1) {
logger.log(Level.WARNING, e.getMessage(), e);
}
return false;
}
}
public List<Entry> getLastPoints(int nb) throws IOException {
File file = getFile();
RandomAccessFile raf = null;
List<Entry> result = null;
try {
raf = new RandomAccessFile(file, "r");
long pos = raf.length() - (nb * DATA_LEN);
if (pos < 0) {
nb = nb + (int) (pos / DATA_LEN);
pos = 0;
}
raf.seek(pos);
result = new ArrayList<Entry>(nb);
Entry next = null;
for (int i = 0; i < nb; i++) {
next = new Entry();
next.timestamp = (long) raf.readInt();
next.value = raf.readFloat();
result.add(0, next);
}
} finally {
if (raf != null) raf.close();
}
return result;
}
public static void main(String args[]) {
try {
String fname = "d:\\q.txt";
String mode;
// mode = "r";//r : file must exist
mode = "rw"; // rw : file will be created or opened
// open the file
RandomAccessFile raf = new RandomAccessFile(fname, mode);
/*
//seek and write demo
raf.seek(10);//position file r/w pointer at index 10 wrt BOF
//a seek beyond file size causes file to grow upto the seek value
raf.write(65);//raf.write('A');
*/
// r/w java datatypes
int i1, i2;
float f1, f2;
char c1, c2;
String s1, s2;
i1 = -10;
f1 = 1234.5678F;
c1 = 'q';
s1 = "hello files";
raf.seek(0); // reach BOF
raf.writeInt(i1);
raf.writeFloat(f1);
raf.writeChar(c1);
raf.writeUTF(s1);
raf.seek(0); // reach BOF
i2 = raf.readInt();
f2 = raf.readFloat();
c2 = raf.readChar();
s2 = raf.readUTF();
System.out.println(i2);
System.out.println(f2);
System.out.println(c2);
System.out.println(s2);
// close the file
raf.close();
} catch (IOException ex) {
System.out.println(ex); // ex converts into ex.toString()
}
} // main
public static void main(String args[]) {
RandomAccessFile classe = null;
Scanner entrada = new Scanner(System.in);
Aluno b = new Aluno();
boolean achou = false;
float media;
try {
classe = new RandomAccessFile("c:\\alunos.dat", "rw");
achou = false;
while (true) {
b.numero = classe.readInt();
b.nome = classe.readUTF();
b.curso = classe.readUTF();
b.nota1 = classe.readFloat();
b.nota2 = classe.readFloat();
media = (float) ((b.nota1 + b.nota2) / 2);
if (media >= 7) {
System.out.print("\nNome: " + b.nome);
System.out.print("\nCurso: " + b.curso);
System.out.print("\nNota1: " + b.nota1);
System.out.print("\nNota2: " + b.nota2);
System.out.print("\nMedia: " + media + "\n");
}
}
} // fim try
catch (EOFException e) {
try {
classe.close();
} // fim try
catch (IOException e2) {
System.out.println("\nErro de I/O");
}
} // fimn catch (EOFException e)
catch (IOException e) {
System.out.println("Erro na criacao o arquivo");
}
} // fim main
/**
* Fourni la dernière valeur Le curseur est positionné en fin de dernière valeur (pret à écrire si
* ouvert en rw)
*
* @return
* @throws IOException
*/
private Entry getLast(RandomAccessFile rdf) throws IOException {
if (this.last == null) {
File file = getFile();
long len = file.length();
if (len >= DATA_LEN) {
// Il y a des données dans le fichier : lecture
boolean closeFileFlag = false;
if (rdf == null) {
rdf = new RandomAccessFile(file, "r");
closeFileFlag = true;
}
long pos = len - DATA_LEN;
long mod = pos % DATA_LEN;
if (mod != 0) {
logger.warning(
"Taille de fichier incoherence ("
+ len / DATA_LEN
+ "x"
+ DATA_LEN
+ ", reste "
+ mod
+ "). retour a "
+ (len - mod));
pos -= mod;
}
rdf.seek(pos);
last = new Entry();
last.timestamp = (long) rdf.readInt();
last.value = rdf.readFloat();
logger.fine("dernier enregistrement: " + last);
if (closeFileFlag) rdf.close();
}
}
return this.last;
}
/** This reads a binary float from the file. */
public float readBinaryFloat(int col, int row) throws IOException {
raf.seek(row * nBytesPerRow + columnStartAt[col]);
return raf.readFloat();
}
/* @see java.io.DataInput.readFloat() */
public float readFloat() throws IOException {
return raf.readFloat();
}