FileReader question 1

[tikual]

Hi all,

Suppose a file contains "abcd", why FileReader can read the char in 'a', 'b', 'c', 'd' but not 'ab' and 'cd'? Why not it reads 16 bits a times?

Thanks,

tikual

 

[timw]

There's a read method on the FileReader class which can read multiple characters into an array.

Tim

 

[tikual]

Hi Tim,

I confused in the difference between the read method of FileReader and FileInputStream. How many bit it reads a times? Not 16 bit and 8 bit? If I output the file from these two streams, both return the same content of "abcd" file. So what is the difference?

Thanks!

tikual

 

[timw]

FileReader is intended for files containing textual information, whereas FileInputStream deals with Files as a collection of bytes.

Tim

 

[tikual]

Hi Tim,

Let's see my simple code:

The content of "source.txt" is "abcd". How to explan that the System.out.println shows the same value in these two loops? I understand the purpose of these two classes. But, it returns the same value per each cycle. I would like to know how many bits it reads of FileReader and FileInputStream respectively.



import java.io.*;

public class TwoStreamWriter{
public static void main(String[] args)throws IOException{
File input = new File("source.txt");
InputStream in = new FileInputStream(input);
OutputStream out = new FileOutputStream("output1.txt");

int byteRead;
while ( (byteRead = in.read()) != -1 ){
System.out.println(byteRead);
out.write(byteRead);
}
in.close();
out.close();

Reader reader = new FileReader(input);
Writer writer = new FileWriter("output2.txt");

int charRead;
while ( (charRead = reader.read()) != -1 ){
System.out.println(charRead);
writer.write(charRead);
}

reader.close();
writer.close();
}
}

tikual

 

[sedj]

According to the API, FileInputStream.read() reads a byte (8 bits), and a FileReader.read() reads a character (16 bits).

I **think** this can be explained by the following ...

Now, the int values of 'a' 'b' 'c' and 'd' are, respectively 97 98 99 100 . These ints fit into a byte structure - because, while an int can be 32 bits, a small number, like those above, will not fill all those bits.
Hence, when the filereader reads the char, not all the 16 bits are used - so you see the same output.

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[tikual]

Hi sedj,

Thanks for your help!!!

tikual