I/O in Java - Java for COBOL Programmers - page 250

InputStream defines three basic methods of reading data:

Method Description

read() Abstract method that reads a single byte and returns its value as an

integer

read(byte [] data) Reads bytes to fill the byte array and returns the number of bytes read

read(byte [] data, Reads bytes to fill the byte array at the selected point and returns the

int offset, int len) number of bytes read

The classes that extend InputStream will override these methods to handle the un-
derlying storage or transport media. A FileInputStream will read data from disk. An
InputStream obtained from a network connection will read data from a TCP/IP con-
nection. The logic for performing the reading remains essentially the same because in
both cases the logic is using the InputStream methods for reading and writing.

Method Description

write(int b) Abstract method that writes a single byte

write (byte [] data) Writes all the bytes from the byte array

write(byte [] data, Writes selected bytes from the byte array

int offset, int len)

OutputStream parallels InputStream in having three basic methods for writing data:
To illustrate the usage of InputStream s and OutputStream s, I am going to extend
the earlier example and create a simple file-copy program. A simple file-copy pro-
gram in COBOL would look something like this:

FD INPUT-FILE.
01 INPUT-RECORD.
05 FILLER PIC X(100).

FD OUTPUT-FILE.
01 OUTPUT-RECORD.
05 FILLER PIC X(100).

OPEN INPUT INPUT-FILE.
OPEN OUTPUT OUTPUT-FILE.