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關(guān)于流

我一直對流都有點暈暈的，今天基本算搞清楚了所以然，所以在這里寫出，一來為了記憶，一來也希望能對和我一樣在這里有點模糊的一點幫助。（呵呵，不會就我一個人這么倒霉吧？）?

輸入流：此流對應(yīng)于鍵盤輸入或者由主機環(huán)境或用戶指定的另一個輸入源

超類： InputStream (System.in 就屬于這類 )

輸出流：此流對應(yīng)于顯示器輸出或者由主機環(huán)境或用戶指定的另一個輸出目標。

超類： OutputStream (System.out 就屬于這類。其實 System.err 也是間接屬于它 )

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一切都是流！

看一段程序

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?1 /**/ /*
?2 ?*?ThreadedEchoServer.java
?3 ?*
?4 ?*?Created?on?2006年10月14日,?上午11:57
?5 ? */
?6
?7 package ?corejava;
?8
?9 import ?java.io.IOException;
10 import ?java.io.InputStream;
11 import ?java.io.OutputStream;
12 import ?java.io.PrintWriter;
13 import ?java.net.ServerSocket;
14 import ?java.net.Socket;
15 import ?java.util.Scanner;
16
17 /**?*/ /**
18 ?*
19 ?*? @author ?livahu
20 ? */
21 public ? class ?ThreadedEchoServer? {
22 ????
23 ???? /**?*/ /** ?Creates?a?new?instance?of?ThreadedEchoServer? */
24 ???? public ?ThreadedEchoServer()? {
25 ????}
26 ????
27 ???? public ? static ? void ?main(String[]?args)? {
28 ???????? try ? {
29 ???????????? int ?i? = ? 1 ;
30 ????????????ServerSocket?s? = ? new ?ServerSocket( 8189 );
31 ????????????
32 ???????????? while ?( true )? {
33 ????????????????Socket?incoming? = ?s.accept();
34 ????????????????System.out.println( " Spawning? " ? + ?i);
35 ????????????????Runnable?r? = ? new ?ThreadedEchoHandler(incoming,?i);
36 ????????????????Thread?t? = ? new ?Thread(r);
37 ????????????????t.start();
38 ????????????????i ++ ;
39 ????????????}
40 ????????} ? catch ?(IOException?ex)? {
41 ????????????ex.printStackTrace();
42 ????????}
43 ????}
44 }
45
46 class ?ThreadedEchoHandler? implements ?Runnable? {
47 ???? private ?Socket?incoming;
48 ???? private ? int ?counter;
49 ????
50 ???? public ?ThreadedEchoHandler(Socket?i,? int ?c)? {
51 ????????incoming? = ?i;
52 ????????counter? = ?c;
53 ????}
54 ????
55 ???? public ? void ?run()? {
56 ???????? try ? {
57 ???????????? try ? {
58 ????????????????InputStream?inStream? = ?incoming.getInputStream();
59 ????????????????OutputStream?outStream? = ?incoming.getOutputStream();
60 ????????????????
61 ????????????????Scanner?in? = ? new ?Scanner(inStream);
62 ????????????????PrintWriter?out? = ? new ?PrintWriter(outStream,? true );
63 ????????????????out.println( " Hello!?Enter?BYE?to?exit. " );
64 ????????????????
65 ???????????????? boolean ?done? = ? false ;
66 ???????????????? while ?( ! done? && ?in.hasNextLine())? {
67 ????????????????????String?line? = ?in.nextLine();
68 ????????????????????out.println( " Echo:? " ? + ?line);
69 ???????????????????? if ?(line.trim().equals( " BYE " ))
70 ????????????????????????done? = ? true ;
71 ????????????????}
72 ????????????} ? finally ? {
73 ????????????????incoming.close();
74 ????????????????
75 ????????????}
76 ????????} ? catch ?(IOException?ex)? {
77 ????????????ex.printStackTrace();
78 ????????}
79 ????}
80 ????
81 }
82

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我們來分析其中一段?
?????????????????InputStream inStream = incoming.getInputStream();

??????????????? OutputStream outStream = incoming.getOutputStream();

???????????????

??????????????? Scanner in = new Scanner(inStream);

??????????????? PrintWriter out = new PrintWriter(outStream, true);

??????????????? out.println("Hello! Enter BYE to exit.");

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incoming?是一個Socket對象，getInputStream()方法返回一個InputStream對象，用于接受用戶從文件或者鍵盤或者其它源的輸入。而getOutputStream() 方法用來返回一個OutputStream對象，用來得到一個Socket的輸出流，再用PrintWriter包裝它（或叫結(jié)合產(chǎn)生過濾流）為了更方便的輸出。利用out對象的println(String s)方法，我們可以把s的數(shù)據(jù)輸出到out的緩沖區(qū)里面，然后如果數(shù)據(jù)滿了緩沖區(qū)自動經(jīng)過底層流輸出到顯示器或者由主機環(huán)境或用戶指定的另一個輸出目標，這里就是telnet應(yīng)用程序窗口,而不是command控制臺，如果數(shù)據(jù)未寫滿緩沖區(qū)println()也會自動調(diào)用flush()方法刷新緩沖區(qū)，輸出數(shù)據(jù)。

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