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Article #2488Java Q&A (GB��) (��)
From: �ڰ�֮��
Date: Sat, 20 Dec 1997 00:00
Date: Sat, 20 Dec 1997 00:00
701 lines
16458 bytes
16458 bytes
JAVA Q&A����
�����ϲ���Ӵ.................
��һ�ʡ�
: ������javac����õ�class�Dz���һ��Ҫ����java\lib�²�����java��run
: �ұ�������java�����ѽ���һ����Ŀ¼�����Լ�д�õ�һЩ��ʽ,
: ����ÿ�α������Ҫ��java��runʱ������֪�Ҳ�����һ��class,
: �����Ұ��ұ�����class copy ��libĿ¼�¾���ִ��,
: �Dz���һ��Ҫ�����鷳��?Ϊʲ��java��"������"����Ŀ¼�µ�class��?
: ps:�ҵ�Ŀ¼����:
: c:\java+----bin
: +----lib----�ҵ�classpath�趨����
: +----include
: +----exercise---�������ִ��java,*.class,*.javaҲ����
: and.�ҽ�bin����path��...
: �
ֻҪ Set CLASSPATH ������������÷ֺŷָ���� Path
Set CLASSPATH = .... ; ...... ; ......
�ڶ��ʡ�
: �ҵij�ʽ�ڱ����ʱ����������µ�ѶϢ:
: failed to read:C:\JAVA\BIN\...\lib\javac.propeties
: Motorcycle.java:22:error message'toplevel.expected' not found
: Motorcycle Nsr;
: ^
: ��ΪѧУû��Java�Ŀγ�,���������Լ�����ѧ��,���Java�Ĺ���������
: �����������һ�����д?ϣ���Ҷ��ָ��....
: �ҽ���ʽ�븽�ڵ���,ϣ���ܹ��õ���ı������,лл!
: package TrafficTools; //���һ����Ϊ TrafficTools��package
: //��������һ��һ��Ҫimport�κ������?
: (����:java.applet.Applet)//
��һ�� �������Ҫ������� but default import java.lang.*
: //��Ҫ����һ�������沢����Motorcycleȥimplements��?
��һ�� ��������Ҫʱ
:
: Motorcycle Nsr; //���NsrΪMotorcycle�������,���̳�Motorcycle
: Nsr=new Motorcycle(); //����Nsr���
: Nsr.Count(); //����Nsr���ʹ�� Count() ��һ��method
��������Ҫд�� Motorcycle class �� main Function �� ��Ϊ�ⲻ���� C++
class Motocycle {
// һ�� Java Application (not Applet) һ��Ҫ�е� function
public static void main(String Args[]) { // ��ʽ�����
Motorcycle Nsr;
Nsr = new Motorcycle();
Nsr.Count;
}
}
�����ʡ�
: �����뽫���applet����homepage��,��ҲҪд main function��??
: main function�����ܷ���homepage�ϰ�....
�� !! application ����Ҫ�� !! applet ���� init() �� Motorcycle Ҫ�̳�
applet . ��� new Motorcycle Object ������ Browser ����
: ����һ�������� Motorcycle Nsr;
: Nsr = new Motorcycle();
: Nsr. Count();
: ������һ��Ҫд��Motorcycle����������?
: ��ָ��,лл!
Yes ...
Java û�� Gobal ���κζ���
�����ʡ�
> : ��˵CGI��ʽ�������κγ�ʽ������д��������ɲ�������Java��д�ء�
> : �����ԡ�����
> : Ҫ���Ǹ�class��method��ȡ��client�����������ء���ͨ����stdin��Ҫ����д��
> : ��client��Ҫ��κ���server��Java CGI��ʽ����
: action="http://xxx.dom.???.tw/cgi-bin/___________">
> �ٲ���һ�¡�����win95�¡�������symbolic link.
1. CGI ������ Java д. ��� Java ��ʽ�� Application ��� Applet.
2. ͨ�������ʽ����������� code:
import java.io.*;
...
DataInputStream instring = new DataInputStream(System.in);
PrintStream outstring = new PrintStream(System.out);
string HTMLout;
while ((input = instring.readLine()) != null) {
// Do what the CGI program should do
// then, write output using outstring.println(HTMLout);
}
outstring.close();
...
3. ��� Client ����κ���, ����һ������. �����
ACTION="http://xxx.dom.???.tw/cgi-bin/xxx.class"
��� Web server ֱ��֧Ԯִ�� Java ��ʽ, ����, ��������.
Java ��ʽ������ interpreter ִ�е�. ���ܵ�һ����ͨ����,
����ִ��ij������ shell �ij�ʽ (�� *.bat, ������ Win95),
����ִ�� java xxx.class. ��û���Թ��Ƿ����?
4. ����Ҫ symbolic link.
�����ʡ�
>: : ����һ��Ҫ�����TextField����������?
>: : лл
>: Java ��Ԫ�� Unicode,���� big5 ����ܲ���.
> лл<
> ���������TextField��AppletҪ�����
> Webʹ��������������?
Ŀǰ��֪��ֻ����copy & paste ����big5������ !
�����ʡ�
>�����ѧjava
�����������վ̨:http://atmwww.cm.nctu.edu.tw/~duann/javascript/script.html
�����ʡ�
����һ��ѧϰ Java script ��վ
http://www.essex1.com/people/timothy/js-index.htm
������ clock,banner,timer,color �� java script
����!!
�ڰ��ʡ�
: I have a problem about use a Applet to communicate with web server's CGI
: program. Explan as below:
�Ҳ�ԭ����
: try{
: URL sortURL=new URL("http://my.address/cgi-bin/test.sh");
^^^^^^^^^^ ��߲���hard-coded
һ��Ҫ��getCodeBase().getHost()
��ΪSecurityManager��ȥ����hostname
�뺬�����applet��homepage��URL��
��hostname���ִ��ıȶ�,�����hostname
��IP address�Ƿ��Ӧ��ͬһ̨����,ֻҪ��һ��
�ͻ���SecurityException,���ѶϢӦ������
browser�����status����
: URLConnection connection= sortURL.openConnection();
: PrintStream outStream=new PrintStream(connection.getOutputStream());
: outStream.println("my data to send");
: outStream.close();
: }
: catch........I have a problem about use a Applet to communicate with web server's CGI
�ھ��ʡ�
: С���и��ɻ����
: ��:
: imports java.awt.Graphics
: java.awt�Ǹ�PACKAGE
: �����Graphics��Class
: ��� m...û����,�������
: ��...��:
: System.out.println("...");
: System.out�DZ���??
: ��������Method?? ����...д��javaһ���ڼ�,ÿ��д��������������..
: System�����֪�Ǻη���ʥ?? ��package ,��class ����variable
: ���������Ժ�.. ��˭��˵˵System������implement ������?
: bye~
���:
�������������(�������!):
���г� System ��� class:
public final class java.lang.System extends java.lang.Object
{
// Fields
public static PrintStream err; ��
public static InputStream in; ��
public static PrintStream out; ��
// Methods
public static void ��
arraycopy(Object src, int src_position,
Object dst, int dst_position, int length);
public static long currentTimeMillis(); ��
public static void exit(int status); ��
public static void gc(); ��
public static Properties getProperties(); ��
public static String getProperty(String key); ��
public static String getProperty(String key, String def); ��
public static SecurityManager getSecurityManager(); ��
public static void load(String filename); ��
public static void loadLibrary(String libname); ��
public static void runFinalization(); ��
public static void setProperties(Properties props); ��
public static void setSecurityManager(SecurityManager s); ��
}
����Կ��� in �� out ���� class variables,����Ҫʹ���������ȫ��,�� System.in
�� in �� out(����err) ���� reference,in ��һ�� InputStream ����� reference,
out ��һ�� PrintStream ����� reference,�� System �� class �� load ����ʽ��ʱ,
����Զ�����һ�� InputStream(PrintStream) �����,Ȼ����� in(out) ��� variable,
���� in(out) �Ϳ���ʹ�� InputStream(PrintStream) ����� instance methods.
����֪�����?
��ʮ�ʡ�
: �����ѱ���õ� CGI ��ʽ�Ƿ�һ��Ҫ���� server �˵�����Ŀ¼��???
: ���û����·����(����) ����β���?
: PS:�� VB д
> NCSA���httpd��������CGI��ʽ��,*.cgi�ķ�ʽ���ڲ�ִ�ж�ط��� server
> �˵�����Ŀ¼��,����������Կ���,����еĻ��������㻹�������
> ������װһ��server���ܿ��Խ��.
> �����ɹ���������������ɵ�!!
����Ļ��������а취�����ֻ��һЩunix�ϵ�ָ������������trouble
���ȿɼܸ�ncsa��whttpd (��֪����95��???)
����VB�Ļ����ҵ������ǽ���compiler��exe���c:\httpd\cgi-winĿ¼��
����perl�Ļ����ͼܸ�perl5��c:\usr\local\lib\perl�¡���ȻҪ��pif��
��httpd.cnf�������ġ�Ȼ�Ὣ*.pl����c:\httpd\cgi-dosĿ¼��
��http://127.0.0.1/cgi-dos/*.pl �� http://127.0.0.1/cgi-win/*.exe
�Ϳ��ڵ���ִ��cgi��ʽ��test ok֮����upload��server�С���ʡǮ˵��
�����д?��ָ�̡�
*�ԡ�lynx 2.5 Ҳ���Ե����� CGI ��ʽ�����谲װ httpd��
*��95��nt��, �����Լ���һ�������ip
�ټӸ�վ, Ȼ��http���Ǹ�ip�Ϳ�����
��ʮһ�ʡ�
: : Ҳ����˵Ҫ��ΰ�: *.class ===> *.java
: : ת��
: Ŀǰ������.
�����Ͽ���
http://web.inter.nl.net/users/H.P.van.Vliet/mocha.htm
��ʮ���ʡ�
: ��������getGraphicsʱ
: ��Ҫ��Ҫoff-screen ��image
: �������image����off-screen ���ء�����
��!off-screen��˵�㲻�Ǵӵ���ץ������image
���Ǵ�createImage(������������˻�Ҫ����)���method
��������Image�����ϼ���֮������˵��?
��ʮ���ʡ�
: I have a problem about clipRect(..),a member function of
: class Graphics..
: In my applet,I must update two parts of Rectangle when a
: paint event is driven.So I wrote the program as follow..
: public void paint(Graphics g){
: :
: g.clipRect(..); // first part needs to update
: :
: g.clipRect(..); // second part needs to update
: :
: }
: But the result was so strange.Only the first part could be
: updated.Second part would not be active.
: Why? Who can tell my how to solve the problem? Thanks!
This method will set a clipping rectangle for this graphics context.
The resulting clipping area is the intersection of the current clipping area
~~~~~~~~~~~~
and the specified rectangle.
Thus, after the first calling of this method, the "current" clipping area
would be the first rectangle part, and if the second rectangle part were
a standalone one(that is, without intersecting in first part), then the
"current" clipping area might be EMPTY!(becouse no intersection) That is
why the second action was fail.
In my opinion, you can try to put a code between these two methods calling,
such as:
:
g.clipRect(..);
:
g.clipRect(the whole graphic(image) area); //new added line
:
g.clipRect(..);
:
**Thanks for your help.I have made an experiment about you
suggestion.I found somethings right,but still somethings
wrong what you wrote above!
In your opinions,the intersaction effect of clipped areas
was correct.But the method to reset the clipped area you
suggested was wrong.Clipped area could not be reseted by
the method of
g.clipRect(full area of graphics); or
g.clipRect(0,0,0,0);
in my experiment.
But
I have a new solution about this problem.This solution use
the method,Graphics::create(),to get a new copy of current
graphics context. You can re-clip the demanded area in the
new Graphics object & then do what you want to do.By this
way, you can avoid the intersaction effect of clipped areas.
����������������? �����κν��顡��д���Ÿ����ǰ�!! С���ᾡ�������ܵ��ġ�
Copyright (c) 1996 BluesTown Music & Internet Centre.
Last modified: Wednesday, August 07 1996 01:55
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X-Google-Language: Chinese,GB X-Google-Thread: fc86e,7c628eee10119be6,start X-Google-Attributes: gidfc86e,public From: Uni.bbs@bbs.njtu.edu.cn (�ڰ�֮��) Subject: Java Q&A (GB��) (��) Date: 1997/12/20 Message-ID: <3MCZgg$tvC@bbs.njtu.edu.cn> X-Deja-AN: 309545420 X-Filename: Programming/M.882606858.A Organization: ��������ɰ��ļ� Newsgroups: cn.bbs.comp.program