1. package com.abc.handoff;
2.  
3. import com.abc.pp.stringhandoff.*;
4. import com.programix.thread.*;
5.  
6.  
7. public class StringHandoffImpl implements StringHandoff {
8.  
9.  
10.     private boolean isShutdown = false;
11.  
12.     private String message = null;
13.  
14.     private boolean isReceiving = false;
15.  
16.  
17.     @Override
18.     public synchronized void pass(String msg, long msTimeout)
19.         throws InterruptedException, TimedOutException, ShutdownException, IllegalStateException {
20.  
21.         throwIfShutdownOrPassing();
22.         passAndNotify(msg);
23.  
24.         long messagesend = System.currentTimeMillis() + msTimeout;
25.         while ( message != null ) {
26.             long messagewait = messagesend - System.currentTimeMillis();
27.             if ( messagewait <= 0 ) {
28.                 throw new TimedOutException();
29.             }
30.  
31.             wait(messagewait);
32.  
33.             if ( isShutdown ) {
34.                 throw new ShutdownException();
35.             }
36.         }
37.  
38.     }
39.  
40.  
41.     @Override
42.     public synchronized void pass(String msg) throws InterruptedException, ShutdownException, IllegalStateException {
43.  
44.         throwIfShutdownOrPassing();
45.         passAndNotify(msg);
46.  
47.         while ( message != null ) {
48.             wait();
49.  
50.             if ( isShutdown ) {
51.                 throw new ShutdownException();
52.             }
53.         }
54.     }
55.  
56.  
57.     @Override
58.     public synchronized String receive(long msTimeout)
59.         throws InterruptedException, TimedOutException, ShutdownException, IllegalStateException {
60.  
61.         throwIfShutdownOrReceiving();
62.  
63.         long messagesend = System.currentTimeMillis() + msTimeout;
64.         while ( message == null ) {
65.             long messagewait = messagesend - System.currentTimeMillis();
66.             if ( messagewait <= 0 ) {
67.                 throw new TimedOutException();
68.             }
69.  
70.             wait(messagewait);
71.  
72.             if ( isShutdown ) {
73.                 throw new ShutdownException();
74.             }
75.         }
76.  
77.         return receiveAndNotify();
78.     }
79.  
80.  
81.     @Override
82.     public synchronized String receive() throws InterruptedException, ShutdownException, IllegalStateException {
83.  
84.         throwIfShutdownOrReceiving();
85.  
86.         // while there is no message, wait.
87.         while ( message == null ) {
88.             wait();
89.  
90.             if ( isShutdown ) {
91.                 throw new ShutdownException();
92.             }
93.         }
94.  
95.         return receiveAndNotify();
96.     }
97.  
98.  
99.     @Override
100.     public synchronized void shutdown() {
101.         isShutdown = true;
102.         message = null;
103.         isReceiving = false;
104.  
105.         notifyAll();
106.     }
107.  
108.     @Override
109.     public Object getLockObject() {
110.         return this;
111.     }
112.  
113.  
114.     private synchronized void passAndNotify(String msg) {
115.         if (msg == "orange") {
116.             System.out.println(isReceiving);
117.         }
118.         message = msg;
119.         notifyAll();
120.     }
121.  
122.  
123.     private synchronized String receiveAndNotify() {
124.         String msg = message;
125.         message = null;
126.         isReceiving = false;
127.  
128.         notifyAll();
129.  
130.         return msg;
131.     }
132.  
133.  
134.     private synchronized void throwIfShutdownOrReceiving() throws ShutdownException, IllegalStateException {
135.         if ( isShutdown ) {
136.             throw new ShutdownException();
137.         }
138.  
139.         if ( isReceiving ) {
140.             throw new IllegalStateException();
141.         }
142.  
143.         isReceiving = true;
144.     }
145.  
146.     private synchronized void throwIfShutdownOrPassing() throws ShutdownException, IllegalStateException {
147.         if ( isShutdown ) {
148.             throw new ShutdownException();
149.         }
150.  
151.         if ( message != null ) {
152.             throw new IllegalStateException();
153.         }
154.     }
155. }
156.  
157.