Me pueden explicar este codigo

[-thor-]

Hola, me podrian explicar para que sirve escribir while (i != -1) en ese ciclo, no entiendo cual es la funcion del valor -1 y luego para que sirve la parte de pw.print((char) i);.

En realidad no entiendo la funcion de esta parte en el codigo
ServletInputStream in = request.getInputStream();
int i = in.read();
while (i != -1) {
pw.print((char) i);
i = in.read();

gracias

Código:

import java.io.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.ServletInputStream;
public class FileUploadBean {
	
public void doUpload(HttpServletRequest request) throws
IOException {
PrintWriter pw = new PrintWriter(
new BufferedWriter(new FileWriter("Demo.out")));
ServletInputStream in = request.getInputStream();
int i = in.read();
while (i != -1) {
pw.print((char) i);
i = in.read();
}
pw.close();
}
}

[cptanalatriste]

De la documentación de InputStream (http://java.sun.com/j2se/1.4.2/docs/...eam.html#read())

Reads the next byte of data from the input stream. The value byte is returned as an int in the range 0 to 255. If no byte is available because the end of the stream has been reached, the value -1 is returned. This method blocks until input data is available, the end of the stream is detected, or an exception is thrown.

O sea, cuando ya no hay bytes disponibles que leer, el método read devuelve -1; por eso se establece esa condicional en el bucle while.

Saludos, espero sea de ayuda,