Java IO
Source and Destination
The most common sources and destinations are these:
- Files
- Pipes
- Network Connections (Socket)
- In-memory Buffers
- System.in, System.out, System.error
Class Hierarchy
Java IO streams are typically either byte based or character based.
- mostly [XXX]InputStream/OutputStream is byte based
- mostly [XXX]Reader/Writer is character based
Example
Keyboard in -> Console out
Scanner scanner = new Scanner(System.in);
int data = scanner.nextInt();
System.out.println(data);
File in -> Socket out
// input
Reader reader = new FileReader("c:\\data\\myfile.txt");
int data = reader.read();
StringBuilder inputString = new StringBuilder();
while(data != -1){
inputString.append((char) data);
data = reader.read();
}
// output
Socket socket = new Socket(serverName, port);
DataOutputStream output = new DataOutputStream(socket.getOutputStream());
output.writeUTF(StringBuilder);
Pipe in -> Pipe out
import java.io.IOException;
import java.io.PipedInputStream;
import java.io.PipedOutputStream;
public class PipeExample {
public static void main(String[] args) throws IOException {
final PipedOutputStream output = new PipedOutputStream();
final PipedInputStream input = new PipedInputStream(output);
Thread thread1 = new Thread(new Runnable() {
@Override
public void run() {
try {
output.write("Hello world, pipe!".getBytes());
} catch (IOException e) {
}
}
});
Thread thread2 = new Thread(new Runnable() {
@Override
public void run() {
try {
int data = input.read();
while(data != -1){
System.out.print((char) data);
data = input.read();
}
} catch (IOException e) {
}
}
});
thread1.start();
thread2.start();
}
}
