BINARY I/O - Introduction to Java Programming - page 724

new BufferedInputStream( new FileInputStream(sourceFile));

34
35
36

// Create an output stream

37
38
39
40

BufferedOutputStream output = output stream

new BufferedOutputStream( new FileOutputStream(targetFile));

// Continuously read a byte from input and write it to output

41 int r, numberOfBytesCopied = 0 ;

r = input.read() read

write

42 while (( ) != -1 ) {

43
44 numberOfBytesCopied++;
45 }
46
47 // Close streams
48 input.close();
49 output.close();
50
51 // Display the file size
52 System.out.println(numberOfBytesCopied + " bytes copied" );
53 }
54 }

output.write(( byte )r);

close stream

The program first checks whether the user has passed the two required arguments from the
command line in lines 10-14.
The program uses the File class to check whether the source file and target file exist. If
the source file does not exist (lines 18-22) or if the target file already exists (lines 25-30), the
program ends.
An input stream is created using BufferedInputStream wrapped on FileInputStream
in lines 33-34, and an output stream is created using BufferedOutputStream wrapped on
FileOutputStream in lines 37-38.
The expression ((r = input.read()) != -1) (line 42) reads a byte from
input.read() , assigns it to r , and checks whether it is -1 . The input value of -1 signifies
the end of a file. The program continuously reads bytes from the input stream and sends them
to the output stream until all of the bytes have been read.

19.22 How does the program check if a file already exists?
19.23 How does the program detect the end of the file while reading data?
19.24 How does the program count the number of bytes read from the file?

✓ ✓

Check

Point

19.6 Object I/O
ObjectInputStream / ObjectOutputStream classes can be used to read/write
serializable objects.

Key
Point

DataInputStream / DataOutputStream enables you to perform I/O for primitive type val-
ues and strings. ObjectInputStream / ObjectOutputStream enables you to perform I/O
for objects in addition to primitive type values and strings. Since ObjectInputStream /
ObjectOutputStream contains all the functions of DataInputStream /
DataOutputStream , you can replace DataInputStream / DataOutputStream com-
pletely with ObjectInputStream / ObjectOutputStream .
ObjectInputStream extends InputStream and implements ObjectInput and
ObjectStreamConstants , as shown in Figure 19.15. ObjectInput is a subinterface of
DataInput ( DataInput is shown in Figure 19.9). ObjectStreamConstants contains the
constants to support ObjectInputStream / ObjectOutputStream .

VideoNote

Object I/O