Hardware description language - Software Development Case Studies in Java - page 115

public class Keyboard {
Bus bus;
public Keyboard(Bus bus) {
this .bus # bus;
}
BufferedReader lineReader # new BufferedReader(
new InputStreamReader( System.in ) );
void execute() {
if (bus.command.equals(Bus.INPUT)) {
try {
System.out.print("> ");
bus.data # lineReader.readLine();
}
catch (IOException ioe) {
ioe.printStackTrace();
bus.data # "";
}
bus.command # Bus.ACK;
}
}
}
The simplest class is Display . Its execute() method waits for the OUTPUT
command, then prints the string lying on the data bus to the default output
and acknowledges the command.
public class Display {
Bus bus;
public Display(Bus bus) {
this .bus # bus;
}
void execute() {
if (bus.command.equals(Bus.OUTPUT)) {
System.out.println("\n> " ! bus.data);
bus.command # Bus.ACK;
}
}
}
The HardDisk class is similar to the Keyboard class in that it is based on a
BufferedReader . In addition to a command to read a line from the reader, it
recognizes two other commands: one initializes the reader to read from a
file, the other closes the file. The execute() method recognizes the commands
FOPEN , FCLOSE and FREAD . At each operation it checks for exceptions; if
an exception is caught it prints an error message and acknowledges the
command to avoid deadlocks.
public class HardDisk {
Bus bus;