While using FileReader class in java why is it compulsory to store the value of r.read in i first and then type caste it? why can't we typecast r.read - memory-management

Question

[it is giving wrong output when I use f1.read directly .. why is it compulsory to use (i=f1.read) and then type caste i into the file .. why can't we use f1.read directly..] 1
//why this code is giving wrong output
// why is it compulsory to first store the value of f1.read in i
import static java.lang.System.out;
import java.io.*;
import java.util.*;
public class third{
public static void main(String [] args) {
try{
FileReader f1 = new FileReader("C:\\Users\\Akshita Agarwal\\Desktop\\a.txt");
FileWriter f2 = new FileWriter("C:\\Users\\Akshita Agarwal\\Desktop\\b.txt");
try{
while(f1.read() !=-1){
f2.write((char)f1.read());
}
}
finally {
f2.close();
}
}
catch(IOException e){
out.println(e);
}
}
}

Answer 1

char is two bytes unsigned. int -1 is outside this range.
Your code does not close f1 and it writes half of the file, every second char.
It could be written as:
for (;;) {
int c = f1.read();
if (c == -1) {
break;
}
f2.write((char)c);
}
You suggestion
for (;;) {
char c = (char) f1.read();
if (c == (char)-1) {
break;
}
f2.write(c);
}
has one drawback.
You could embed a ((char) -1) or '\uFFFF' in the middle of your file, and only
half of the file would be read.
The shortest code is:
for (int c; (c = f1.read()) != -1;) {
f2.write((char)c);
}
However it:
reads and writes per character
there is a conversion reading from binary data using the platform encoding to (Unicode) text
there is a conversion writing from (Unicode) text to binary data using the platform encoding.
Here you could do:
Path path1 = Paths.get("C:\\Users\\Akshita Agarwal\\Desktop\\a.txt");
Path path2 = Paths.get(System.getProperty("user.home"), "Desktop\\b.txt");
Files.copy(path1, path2);
or read by lines:
Charset charset = Charset.defaultCharset();
try (BufferedWriter writer = Files.newBufferedWriter(path2, charset));
Stream<String> reader = Files.lines(path1, charset)) {
reader.forEach(line -> bw.write(line + "\r\n"));
} // Automatically closes reader and writer.
The charset is needed to use the platform encoding. Per default it uses UTF-8, Unicode for the full range of possible characters for all languages.
Try-with-resources is a weird syntax try (<DECLARATIONS>) { ... } that ensures closing of the (auto-)closeable variables in the declarations. Even on return, break or exception.
The lines read are stripped from line endings CR-LF = "\r\n" (Windows), LF (Unix), CR, NEL (AS/400 e.a.).