1. The Java IO System Different kinds of IO Different kinds of operations
Files, blocks of memory, network connections
Different kinds of operations
Sequential, random-access, binary, character, by lines, by words, etc.

2. Typical Uses of IO System
Reading and writing files
Manipulating blocks of memory
Network Programming

3. Streams, Readers & Writers
Java’s stream, reader, and writer classes view input and output as ordered sequences of bytes.
Dealing strictly with bytes would be tremendously bothersome (data appears as bytes, or ints, or floats and so on)
So we need low-level stream and high-level stream.

4. Low-level Streams
Low-level output stream receives bytes and writes bytes to an output device.
Low-level input stream read bytes from an input device and returns bytes to its caller.
Example:
FileInputStream & FileOutputStream
ByteArrayInputStream & ByteArrayOutputStream

5. High-level Streams
A high-level output stream receives general-format data, (ex: primitives), and writes bytes to:
a low-level output stream , or
another high-level output stream
A high-level input stream reads bytes from:
a low-level input stream, or
another high-level input stream
and returns general format data to its caller

6. High-level Streams Examples: DataInputStream & DataOutputStream
BufferedInputStream & BufferedOutputStream

7. High-level & Low-level Streams
DataOutputStream
DataInputStream
FileOutputStream
FileInputStream
writeByte()
readByte()
writeInt()
readInt()
readUTF()
writeUTF()
file
Etc...
Etc….
BufferedOutputStream
BufferedInputStream

8. High-level & Low-level Streams
Example:
FileOutputStream fo =
new FileOutputStream (“my.data”);
BufferedOutputStream bo =
new BufferedOutputStream (fo);
DataOutputStream do = new DataOutputStream (bo);
do.writeChar (‘A’);
do.writeInt (32.5);

9. Reader and Writer Classes
Internationalization: uses 16-bit char instead of 8-bit byte
Also designed to improve speed
Sometimes they can replace InputStream and OutputStream

10. Low-level Readers & Writers
FileReader & FileWriter
CharArrayReader & CharArrayWriter
StringReader & StringWriter
etc….

11. High-level Readers & Writers
BufferedReader & BufferedWriter
InputStreamReader & OutputStreamWriter
LineNumberReader
PrintWriter
etc….

12. Readers and Writers PrintWriter OutputStreamWriter FileOutputStream
Text File
BufferedWriter

13. Readers and Writers PrintWriter out = new PrintWriter(
new BufferedWriter(
new OutputStreamWriter(
new FileOutputStream (“TextFile”))));
out.println(str);