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C++与Java基本数据�c�d��比较

greedy — Wed, 19 Nov 2008 03:47:00 GMT

C++与Java基本数据�c�d��及所占用内存�I�间比较

----------------C++------------------------Java----------
(01)01)bool----------------1 byte-----01)boolean--1 byte
(02)02)char----------------1 byte-----02)char-----2 bytes
(03)---signed char---------1 byte 03)byte-----1 byte
(04)---unsigned char-------1 byte
(05)03)wchar_t-------------2 bytes
(06)04)short---------------2 bytes----04)short----2 bytes
(07)---unsigned short------2 bytes
(08)05)int-----------------4 bytes----05)int------4 bytes
(09)---unsigned int--------4 bytes
(10)06)long----------------4 bytes----06)long-----8 bytes
(11)---unsigned long-------4 bytes
(12)07)long long-----------8 bytes
(13)---unsigned long long--8 bytes
(14)08)float---------------4 bytes----07)float----4 bytes
(15)09)double--------------8 bytes----08)double---8 bytes
(16)10)long double--------12 bytes
----------------------------------------------------------

下面C++代码在Code::Blocks 8.02 中测试通过�?/font>

#include
#include
using namespace std;

#define W setw(20)

int main(int argc,char** argv) {
cout.setf(ios_base::right);
cout< cout< cout< cout< cout< cout< cout< cout< cout< cout< cout< cout< cout< cout< cout< cout< return EXIT_SUCCESS;
}

//-----

               bool:1
               char:1
        signed char:1
      unsigned char:1
            wchar_t:2
              short:2
     unsigned short:2
                int:4
       unsigned int:4
               long:4
      unsigned long:4
          long long:8
unsigned long long:8
              float:4
             double:8
        long double:12
//-----

greedy 2008-11-19 11:47 发表评论

greedy — Fri, 10 Oct 2008 09:26:00 GMT

1. MySQL(http://www.mysql.com)mm.mysql-2.0.2-bin.jar
Class.forName( "org.gjt.mm.mysql.Driver" );
cn = DriverManager.getConnection( "jdbc:mysql://MyDbComputerNameOrIP:3306/myDatabaseName", sUsr, sPwd );

2. PostgreSQL(http://www.de.postgresql.org)pgjdbc2.jar
Class.forName( "org.postgresql.Driver" );
cn = DriverManager.getConnection( "jdbc:postgresql://MyDbComputerNameOrIP/myDatabaseName", sUsr, sPwd );

3. Oracle(http://www.oracle.com/ip/deploy/database/oracle9i/)classes12.zip
Class.forName( "oracle.jdbc.driver.OracleDriver" );
cn = DriverManager.getConnection( "jdbc:oracle:thin:@MyDbComputerNameOrIP:1521:ORCL", sUsr, sPwd );

4. Sybase(http://jtds.sourceforge.net)jconn2.jar
Class.forName( "com.sybase.jdbc2.jdbc.SybDriver" );
cn = DriverManager.getConnection( "jdbc:sybase:Tds:MyDbComputerNameOrIP:2638", sUsr, sPwd );
//(Default-Username/Password: "dba"/"sql")

5. Microsoft SQLServer(http://jtds.sourceforge.net)
Class.forName( "net.sourceforge.jtds.jdbc.Driver" );
cn = DriverManager.getConnection( "jdbc:jtds:sqlserver://MyDbComputerNameOrIP:1433/master", sUsr, sPwd );

6. Microsoft SQLServer(http://www.microsoft.com)
Class.forName( "com.microsoft.jdbc.sqlserver.SQLServerDriver" );
cn = DriverManager.getConnection( "jdbc:microsoft:sqlserver://MyDbComputerNameOrIP:1433;databaseName=master", sUsr, sPwd );

7. ODBC
Class.forName( "sun.jdbc.odbc.JdbcOdbcDriver" );
Connection cn = DriverManager.getConnection( "jdbc:odbc:" + sDsn, sUsr, sPwd );

8.DB2(新添�?
Class.forName("com.ibm.db2.jdbc.net.DB2Driver");
String url="jdbc:db2://192.9.200.108:6789/SAMPLE"
cn = DriverManager.getConnection( url, sUsr, sPwd );

补充
Microsoft SQL Server series (6.5, 7.x and 2000) and Sybase 10

JDBC Name: jTDS
URL: http://jtds.sourceforge.net/
Version: 0.5.1
Download URL: http://sourceforge.net/project/showfiles.php?group_id=33291

语法:

Class.forName("net.sourceforge.jtds.jdbc.Driver ");
Connection con = DriverManager.getConnection("jdbc:jtds:sqlserver://host:port/database","user","password");
or
Connection con = DriverManager.getConnection("jdbc:jtds:sybase://host:port/database","user","password");
Postgresql

JDBC Name: PostgreSQL JDBC
URL: http://jdbc.postgresql.org/
Version: 7.3.3 build 110
Download URL: http://jdbc.postgresql.org/download.html

语法:

Class.forName("org.postgresql.Driver");
Connection con=DriverManager.getConnection("jdbc:postgresql://host:port/database","user","password");

IBM AS400��L��在用的JDBC语法

有装V4R4以上版本的Client Access Express
可以在C:Program FilesIBMClient Accessjt400lib
扑ֈ� driver 档案 jt400.zip�Q��ƈ更改扩展名成�?jt400.jar

语法

java.sql.DriverManager.registerDriver (new com.ibm.as400.access.AS400JDBCDriver ());
Class.forName("com.ibm.as400.access.AS400JDBCConnection");
con = DriverManager.getConnection("jdbc:as400://IP","user","password");

informix

Class.forName("com.informix.jdbc.IfxDriver").newInstance();

String url =

"jdbc:informix-sqli://123.45.67.89:1533/testDB:INFORMIXSERVER=myserver;

user=testuser;password=testpassword";

Lib�Q�jdbcdrv.zip

Class.forName( "com.sybase.jdbc.SybDriver" )
url="jdbc:sybase:Tds:127.0.0.1:2638/asademo";
SybConnection connection= (SybConnection)DriverManager.getConnection(url,"dba","sql");

补充两个
SAP DB
Class.forName ("com.sap.dbtech.jdbc.DriverSapDB");
java.sql.Connection connection = java.sql.DriverManager.getConnection ( "jdbc:sapdb://" + host + "/" + database_name,user_name, password)

InterBase
String url = "jdbc:interbase://localhost/e:/testbed/database/employee.gdb";
Class.forName("interbase.interclient.Driver");
//Driver d = new interbase.interclient.Driver (); /* this will also work if you do not want the line above */
Connection conn = DriverManager.getConnection( url, "sysdba", "masterkey" );

HSqlDB

url: http://hsqldb.sourceforge.net/
driver: org.hsqldb.jdbcDriver

�q�接方式�?�U�，分别为：
con-str�Q�内存）: jdbc:hsqldb.
con-str�Q�本圎ͼ�: jdbc:hsqldb:/path/to/the/db/dir
con-str�Q�http�Q? jdbc:hsqldb:http://dbsrv
con-str�Q�hsql�Q? jdbc:hsqldb:hsql://dbsrv
SAP DB
Class.forName ("com.sap.dbtech.jdbc.DriverSapDB");
java.sql.Connection connection = java.sql.DriverManager.getConnection ( "jdbc:sapdb://" + host + "/" + database_name,user_name, password)

InterBase
String url = "jdbc:interbase://localhost/e:/testbed/database/employee.gdb";
Class.forName("interbase.interclient.Driver");
//Driver d = new interbase.interclient.Driver (); /* this will also work if you do not want the line above */
Connection conn = DriverManager.getConnection( url, "sysdba", "masterkey" );
Microsoft SQL Server series (6.5, 7.x and 2000) and Sybase 10

JDBC Name: jTDS
URL: http://jtds.sourceforge.net/
Version: 0.5.1
Download URL: http://sourceforge.net/project/showfiles.php?group_id=33291

语法:

Class.forName("net.sourceforge.jtds.jdbc.Driver ");
Connection con = DriverManager.getConnection("jdbc:jtds:sqlserver://host:port/database","user","password");
or
Connection con = DriverManager.getConnection("jdbc:jtds:sybase://host:port/database","user","password");
Postgresql

JDBC Name: PostgreSQL JDBC
URL: http://jdbc.postgresql.org/
Version: 7.3.3 build 110
Download URL: http://jdbc.postgresql.org/download.html

语法:

Class.forName("org.postgresql.Driver");
Connection con=DriverManager.getConnection("jdbc:postgresql://host:port/database","user","password");

IBM AS400��L��在用的JDBC语法

有装V4R4以上版本的Client Access Express
可以在C:Program FilesIBMClient Accessjt400lib
扑ֈ� driver 档案 jt400.zip�Q��ƈ更改扩展名成�?jt400.jar

语法

java.sql.DriverManager.registerDriver (new com.ibm.as400.access.AS400JDBCDriver ());
Class.forName("com.ibm.as400.access.AS400JDBCConnection");
con = DriverManager.getConnection("jdbc:as400://IP","user","password");
informix数据�?br /> Class.forName("com.informix.jdbc.IfxDriver").newInstance();

String url =

"jdbc:informix-sqli://123.45.67.89:1533/testDB:INFORMIXSERVER=myserver;

user=testuser;password=testpassword";
Sybase数据�?br /> Lib�Q�jdbcdrv.zip

Class.forName( "com.sybase.jdbc.SybDriver" )
url="jdbc:sybase:Tds:127.0.0.1:2638/asademo";
SybConnection connection= (SybConnection)DriverManager.getConnection(url,"dba","sql");

greedy 2008-10-10 17:26 发表评论

讉K��控制

greedy — Fri, 05 Sep 2008 02:24:00 GMT

�c�L��w�也有访问控�Ӟ��卛_��定义�cȝ��class关键字前加上讉K��?/span>制符�Q�但�c�L��w�只有两�U�访问控�Ӟ��?/span>public 和默认，
父类不能�?/span>private �?/span> protected�Q�否则子�c�L��法��ѝ�?/span>public修饰�?/span>�c�能被所有的�c�访问，
默认修饰�Q�即class关键字前没有讉K��控制�W�）的类�Q�只能被同一包中的所有类讉K��?/span>

greedy 2008-09-05 10:24 发表评论

greedy — Wed, 03 Sep 2008 13:02:00 GMT

先看一�D�小�E�序�Q?

---------------------------------------------------------------

1.public class MyClass
2.{
3.      static String s1 = "I am unique!";
4.     public static void main(String args[])
5.    {
6.            String s2 = "I am unique!";
7.           String s3 = new String(s1);
8.           System.out.println(s1 == s2);
9.          System.out.println(s1.equals(s2));
10.          System.out.println(s3 == s1);
11.          System.out.println(s3.equals(s1));
12.          System.out.println(TestClass.s4 == s1);
13.   }
14.}

---------------------------------------------------------------

�q�段�E�序是非常简单的。但是�ؓ什么new出来的对象用�Q�＝判断为false�Q�而基本类型的直接赋值用�Q�＝判断��是true呢？

�q�是因�ؓ在JAVA的对象存储机刉��Q�new出来的一定是对象�Q�而对象在内存中的存贮位置在Heap�Q�堆�Q�中�Q�而基本类型在�E�序中出现的比较频繁�Q�注�Q�JAVA中的基本�c�d��?中，分别是：boolean�Q�char�Q�byte�Q�short�Q�int�Q�long�Q�float�Q�double�Q�，所以通过new产生�q�些对象而将其放入在heap中效率反而不高，所以JAVA直接采取C/C++的方式，也就是不以new来分配其�I�间�Q�而是产生一�U�所谓的“automatic”变量�Q�不在是reference的�Ş式）�Q�来解决效率的问题，此类变量直接放数据��|��q�且�|�于stack�Q�栈�Q�中�Q�因为stack在空间的分配和释放上�Q�效率要好的多。而恰恰是�q�种在内存中位置的不同，在stack中�ؓ基本�c�d��变量分配�I�间�Ӟ��如果stack中有一��L��数据�Ӟ��不在创建新的数据，所以导致这个时候比较的两个基本�c�d��值时�Q�即使用�Q�＝也是true�?/p>

因�ؓJAVA保存了基本类型，而基本类型（入int、char�{�）�q�不具备面向对象的特点，比如拥有�cȝ��对象和方法。所以在JAVA中引入了new出来的基本类型，比如character c �Q?new character( )的�Ş式。基于此�Q�严格的�Ԍ��JAVA�q�不是像��Z��所宣称的是��d��的纯�_�的面向对象语言�?br />
��单点��是
==�Q?/font>
1、比较的是操作符两端的操作数是否是同一个对�?br /> 2、两边的操作数必��L��同一�c�d��的（可以是父子类之间�Q�才能编译通过�?br /> 3、比较的是地址�Q�如果是具体的阿拉伯数字的比较，值相�{�则为TRUE�Q�如�Q?br /> int a=10 �?long b=10L �?double c=10.0都是相同的（为true�Q�，因�ؓ他们都指向地址�?0的堆
equals�Q?/font>
1、比较的是两个对象的内容是否一�?

greedy 2008-09-03 21:02 发表评论

servlet 生成动态图片验证码

greedy — Fri, 27 Jun 2008 02:44:00 GMT

import java.io.*;
import java.util.*;
import com.sun.image.codec.jpeg.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.awt.*;
import java.awt.image.*;

public class ShowImage extends HttpServlet {

private Font mFont=new Font("Times New Roman", Font.PLAIN,18);//讄��字体

//处理post
public void doPost(HttpServletRequest request,HttpServletResponse response)
throws ServletException,IOException {
  doGet(request,response);
}

public void doGet(HttpServletRequest request,HttpServletResponse response)
    throws ServletException,IOException {
//取得一�?000-9999的随机数

    HttpSession session=request.getSession(false);
    //session.setAttribute("getImg",s);
    response.setContentType("image/gif");
    response.setHeader("Pragma","No-cache");
    response.setHeader("Cache-Control","no-cache");
    response.setDateHeader("Expires", 0);
    int width=60,height=20;

    ServletOutputStream out=response.getOutputStream();
    BufferedImage image=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB); //讄��囄��大小�?br />     Graphics gra=image.getGraphics();
    Random random=new Random();

    gra.setColor(getRandColor(200,250));    //讄��背景�?br />     gra.fillRect(0,0,width,height);

    gra.setColor(Color.black); //讄��字体�?br />     gra.setFont(mFont);

   /* gra.setColor(new Color(0));
    gra.drawRect(0,0,width-1,height-1);*/

    // 随机产生155条干扰线�Q��图象中的认证码不易被其它�E�序探测�?br />     gra.setColor(getRandColor(160,200));
    for (int i=0;i<155;i++)
    {
     int x = random.nextInt(width);
     int y = random.nextInt(height);
            int xl = random.nextInt(12);
            int yl = random.nextInt(12);
     gra.drawLine(x,y,x+xl,y+yl);
    }

    // 取随��Z�生的认证�?4位数�?
    String sRand="";
    for (int i=0;i<4;i++){
       String rand=String.valueOf(random.nextInt(10));
       sRand+=rand;
        // ��认证码昄��到图象中
        gra.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));//调用函数出来的颜色相同，可能是因为种子太接近�Q�所以只能直接生�?br />         gra.drawString(rand,13*i+6,16);
    }
        //System.out.println("showimage="+sRand);
        session.setAttribute("getImg",sRand);
        JPEGImageEncoder encoder=JPEGCodec.createJPEGEncoder(out);
        encoder.encode(image);
        out.close();

}

  static Color getRandColor(int fc,int bc){//�l�定范围获得随机颜色
         Random random = new Random();
         if(fc>255) fc=255;
         if(bc>255) bc=255;
         int r=fc+random.nextInt(bc-fc);
         int g=fc+random.nextInt(bc-fc);
         int b=fc+random.nextInt(bc-fc);
         return new Color(r,g,b);
  }

}

greedy 2008-06-27 10:44 发表评论

greedy — Fri, 27 Jun 2008 00:52:00 GMT

import java.io.IOException;
import java.awt.event.*;
import javax.swing.*;
public class ShutDown extends JFrame implements ActionListener{
    JButton restart,shutdown,logout;
    Box box;
    public ShutDown(String s) {
        super(s);
        restart=new JButton("重�v");
        shutdown=new JButton("��x��");
        logout=new JButton("注销");
        box=Box.createHorizontalBox();
        restart.addActionListener(this);
        shutdown.addActionListener(this);
        logout.addActionListener(this);
        box.add(restart);
        box.add(shutdown);
        box.add(logout);
        add(box);
        addWindowListener(new WindowAdapter(){
            public void windowClosing(WindowEvent e)
                    {
                      System.exit(0);
                     }
        });
    }
    public void exec(String choice) {
        try {
            Runtime.getRuntime().exec("cmd /c start call shutdown -"+choice+" -t 0");
        }
        catch (IOException e) {
            System.out.println("执行��p�|");
        }
    }

    public void shutdown() {
        exec("S");
    }

    public void restart() {
        exec("R");
    }

    public void logout() {
        exec("L");
    }
  public void actionPerformed(ActionEvent e)
    {
      if(e.getSource()==shutdown)
        {
           shutdown();
        }
        else if(e.getSource()==restart)
        {
           restart();
        }
        else if(e.getSource()==logout)
        {
           logout();
        }
    }
    public static void main(String[] str) {
       ShutDown ctr=new ShutDown("��x��控制");
       ctr.setBounds(300,0,200,65);
       ctr.setVisible(true);
    }
}

greedy 2008-06-27 08:52 发表评论

常用数据库JDBC�q�接写法

greedy — Thu, 26 Jun 2008 14:23:00 GMT

SAP DB
Class.forName ("com.sap.dbtech.jdbc.DriverSapDB");
java.sql.Connection connection = java.sql.DriverManager.getConnection ( "jdbc:sapdb://" + host + "/" + database_name,user_name, password)

InterBase
String url = "jdbc:interbase://localhost/e:/testbed/database/employee.gdb";
Class.forName("interbase.interclient.Driver");
//Driver d = new interbase.interclient.Driver (); /* this will also work if you do not want the line above */
Connection conn = DriverManager.getConnection( url, "sysdba", "masterkey" );

Microsoft SQL Server series (6.5, 7.x and 2000) and Sybase 10

JDBC Name: jTDS
URL: http://jtds.sourceforge.net/
Version: 0.5.1
Download URL: http://sourceforge.net/project/showfiles.php?group_id=33291

语法:

Class.forName("net.sourceforge.jtds.jdbc.Driver ");
Connection con = DriverManager.getConnection("jdbc:jtds:sqlserver://host:port/database","user","password");
or
Connection con = DriverManager.getConnection("jdbc:jtds:sybase://host:port/database","user","password");
Postgresql

JDBC Name: PostgreSQL JDBC
URL: http://jdbc.postgresql.org/
Version: 7.3.3 build 110
Download URL: http://jdbc.postgresql.org/download.html

语法:

Class.forName("org.postgresql.Driver");
Connection con=DriverManager.getConnection("jdbc:postgresql://host:port/database","user","password");

IBM AS400��L��在用的JDBC语法

有装V4R4以上版本的Client Access Express
可以在C:Program FilesIBMClient Accessjt400lib
扑ֈ� driver 档案 jt400.zip�Q��ƈ更改扩展名成�?jt400.jar

语法

java.sql.DriverManager.registerDriver (new com.ibm.as400.access.AS400JDBCDriver ());
Class.forName("com.ibm.as400.access.AS400JDBCConnection");
con = DriverManager.getConnection("jdbc:as400://IP","user","password");

informix数据�?/p>

Class.forName("com.informix.jdbc.IfxDriver").newInstance();

String url =

"jdbc:informix-sqli://123.45.67.89:1533/testDB:INFORMIXSERVER=myserver;

user=testuser;password=testpassword";

Sybase数据�?/p>

Lib�Q�jdbcdrv.zip

Class.forName( "com.sybase.jdbc.SybDriver" )
url="jdbc:sybase:Tds:127.0.0.1:2638/asademo";
SybConnection connection= (SybConnection)DriverManager.getConnection(url,"dba","sql");

greedy 2008-06-26 22:23 发表评论