tucotuco.cs.indiana.edu% ls -ld *.java
-rw-r--r--   1 dgerman  faculty       414 Feb 18 00:28 Peer.java
-rw-r--r--   1 dgerman  faculty       173 Feb 18 00:28 Setup.java
tucotuco.cs.indiana.edu% cat Peer.java
class Peer {
  String name; 
  Peer(String name) {
    this.name = name; 
  }
  void ask(Peer other) {
    System.out.println(other.report()); 
  }
  String report() {
    try {
      return "For " + this.name + " the time is " + 
             new java.util.Date() + "\n on host " + 
             java.net.InetAddress.getLocalHost() + "\n"; 
    } catch (Exception e) {
      return "Error... " + e; 
    } 
  }
}
tucotuco.cs.indiana.edu% cat Setup.java
class Setup {
  public static void main(String[] args) {
    Peer one = new Peer("Larry"); 
    Peer two = new Peer("Michael"); 
    one.ask(two); 
    two.ask(one); 
  }
}
tucotuco.cs.indiana.edu% javac *.java
tucotuco.cs.indiana.edu% ls -ld *      
-rw-r--r--   1 dgerman  faculty       986 Feb 18 00:29 Peer.class
-rw-r--r--   1 dgerman  faculty       414 Feb 18 00:28 Peer.java
-rw-r--r--   1 dgerman  faculty       397 Feb 18 00:29 Setup.class
-rw-r--r--   1 dgerman  faculty       173 Feb 18 00:28 Setup.java
tucotuco.cs.indiana.edu% java Setup
For Michael the time is Wed Feb 18 00:29:52 EST 2004
 on host tucotuco.cs.indiana.edu/129.79.245.110

For Larry the time is Wed Feb 18 00:29:52 EST 2004
 on host tucotuco.cs.indiana.edu/129.79.245.110

tucotuco.cs.indiana.edu%

• report() its date and host name and ip number
• ask(...) another Peer for a report

• Arnold, Gosling, Holmes (starts on p. 538)
• Metsker (not much but some on pp. 122-129)
• Stelting, Maasen (e.g., on p. 311)

"Any major class you expect to be extended, whether abstract or not, should be the implementation of an interface. Although this approach requires a little more work on your part, it enables a whole category of use that is otherwise precluded. For example [...] "

tue0217