How can two threads communicate with each other?

[amgang]

How can two threads communicate with each other?11.

[lionqun]

很长的例子，不过结构清晰（摘于Core Java 卷2)

1. import java.util.*;
2. import java.io.*;
3.
4. /**
5. This program demonstrates how multiple threads communicate
6. through pipes.
7. */
8. public class PipeTest
9. {
10. public static void main(String args[])
11. {
12. try
13. {
14. /* set up pipes */
15. PipedOutputStream pout1 = new PipedOutputStream();
16. PipedInputStream pin1 = new PipedInputStream(pout1);
17.
18. PipedOutputStream pout2 = new PipedOutputStream();
19. PipedInputStream pin2 = new PipedInputStream(pout2);
20.
21. /* construct threads */
22.
23. Producer prod = new Producer(pout1);
24. Filter filt = new Filter(pin1, pout2);
25. Consumer cons = new Consumer(pin2);
26.
27. /* start threads */
28.
29. prod.start();
30. filt.start();
31. cons.start();
32. }
33. catch (IOException e){}
34. }
35. }
36.
37. /**
38. A thread that writes random numbers to an output stream.
39. */
40. class Producer extends Thread
41. {
42. /**
43. Constructs a producer thread.
44. @param os the output stream
45. */
46. public Producer(OutputStream os)
47. {
48. out = new DataOutputStream(os);
49. }
50.
51. public void run()
52. {
53. while (true)
54. {
55. try
56. {
57. double num = rand.nextDouble();
58. out.writeDouble(num);
59. out.flush();
60. sleep(Math.abs(rand.nextInt() % 1000));
61. }
62. catch(Exception e)
63. {
64. System.out.println("Error: " + e);
65. }
66. }
67. }
68.
69. private DataOutputStream out;
70. private Random rand = new Random();
71. }
72.
73. /**
74. A thread that reads numbers from a stream and writes their
75. average to an output stream.
76. */
77. class Filter extends Thread
78. {
79. /**
80. Constructs a filter thread.
81. @param is the output stream
82. @param os the output stream
83. */
84. public Filter(InputStream is, OutputStream os)
85. {
86. in = new DataInputStream(is);
87. out = new DataOutputStream(os);
88. }
89.
90. public void run()
91. {
92. for (;;)
93. {
94. try
95. {
96. double x = in.readDouble();
97. total += x;
98. count++;
99. if (count != 0) out.writeDouble(total / count);
100. }
101. catch(IOException e)
102. {
103. System.out.println("Error: " + e);
104. }
105. }
106. }
107.
108. private DataInputStream in;
109. private DataOutputStream out;
110. private double total = 0;
111. private int count = 0;
112. }
113.
114. /**
115. A thread that reads numbers from a stream and
116. prints out those that deviate from previous inputs
117. by a threshold value.
118. */
119. class Consumer extends Thread
120. {
121. /**
122. Constructs a consumer thread.
123. @param is the input stream
124. */
125. public Consumer(InputStream is)
126. {
127. in = new DataInputStream(is);
128. }
129.
130. public void run()
131. {
132. for(;;)
133. {
134. try
135. {
136. double x = in.readDouble();
137. if (Math.abs(x - oldx) > THRESHOLD)
138. {
139. System.out.println(x);
140. oldx = x;
141. }
142. }
143. catch(IOException e)
144. {
145. System.out.println("Error: " + e);
146. }
147. }
148. }
149.
150. private double oldx = 0;
151. private DataInputStream in;
152. private static final double THRESHOLD = 0.01;
153. }

[wangzhanhai]

这个程序的作用是什么意思？
我看不懂

[amgang]

thanks a lot

[lionqun]

use PipedInputStream and PipedOutputStream

[amgang]

能否仔细说一下再，多谢！！