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《Java学习(f��n)�W�记�?-对象容器之ArrayList和LinkedList

wonderer — Thu, 27 Dec 2007 15:05:00 GMT

去SA面试的时候，面试官问我��^时用Java的什么数据结构，�{�曰�Q�Vector。又问：(x��)哪有用过其他的的吗？例如List和Map之类的。答曎ͼ�(x��)甚少。（自己汗一个，没水�q�I��(j��)既然不会(x��)��p��学习(f��n)啦�?/p>

��d��《Java学习(f��n)�W�记》，里面对对象容器的描述不错�?/p>

1. ArrayList和LinkedList

ArrayList使用�?ji��n)数�l�结构实现List的数据。所以ArraryList用来快速定位对象是非常有效率的。但是如果要对ArraryList中间插入或者删除，效率�?x��)非�怽��?/p>

LinkedList使用链表来实现的List。所以跟ArrayList相反�Q�LinkedList对于插入和删除是非常有优势，反之对于快速定位，是LinkedList的弱��V�?/p>

1)ArrayListDemo

public class ArrayListDemo {
    public static void main(String[] args) {
        
        //用Scanner�c�，可以��L��获得commander的输�?/span>
        Scanner scanner = new Scanner(System.in);
        
        List list = new ArrayList();
        
        //在控制台输入�Q�quit退�?/span>
        while(true) {
            System.out.print("Rokey@console# ");
            String input = scanner.next();
            if(input.equals("quit")) {
                break;
            }
            list.add(input);
        }
        
        System.out.print("昄���输入�Q?);
        
        //使用5.0的foreach功能对List�q�行遍历
        for(String s:list) {
            //5.0的类C的输出格�?/span>
            System.out.printf("%s ",s);
        }
    }
}

输出�Q?/p>

Rokey@console# 一二三
Rokey@console# 三二一
Rokey@console# quit
昄���输入�Q�一二三 三二一

2)用LinkedList实现的一个字�W�串�?/p>

/**
 *
 * @author Rokey
 * 用LinkedList构徏一个字�W�栈�Q�先�q�先�?/span>
 */
public class StringStack {

    private LinkedList linkList;

    public StringStack() {
        linkList = new LinkedList();
    }

    public void push(String s) {
        //���元素加入链表第一个位�|?/span>
        linkList.addFirst(s);
    }

    public String pop() {
        //删除链表�W�一个元素，�q�返�?/span>
        return linkList.removeFirst();
    }

    public String top() {
        //�q�回链表�W�一个元素，但�ƈ不删�?/span>
        return linkList.getFirst();
    }

    public boolean isEmpty() {
        //���(g��)查链表是否�ؓ(f��)�I?/span>
        return linkList.isEmpty();
    }
}

public class StringStackDemo {

    public static void main(String[] args) {

        //用Scanner�c�，可以��L��获得commander的输�?/span>
        Scanner scanner = new Scanner(System.in);

        StringStack stack = new StringStack();

        //在控制台输入�Q�quit退�?/span>
        while (true) {
            System.out.print("Rokey@console# ");
            String input = scanner.next();
            if (input.equals("quit")) {
                break;
            }
            stack.push(input);
        }

        System.out.print("昄���输入�Q?);
        //使用5.0的foreach功能对List�q�行遍历
        
        while(!stack.isEmpty()) {
            //5.0的类C的输出格�?/span>
            System.out.printf("%s ", stack.pop());
        }
    }
}

输出�Q?/p>

Rokey@console# 一二三
Rokey@console# 三二一
Rokey@console# quit
昄���输入�Q�三二一 一二三

wonderer 2007-12-27 23:05 发表评论

wonderer — Sun, 23 Dec 2007 08:46:00 GMT

OYM中的��d��中，有一��对文�g内容的检查挺有意思的�Q�就是要��(g��)查字�W�是否是全角的，例如“�Q�Ｙ”�Q�not“GY”�Q�，�q�且把这些字�W�改为半角的�?br /> 惌��v�?ji��n)在研发中�?j��)的一个朋友的抱怨：(x��)“昨天写了(ji��n)一整天的程序，发到�q�大教务处那边居然说不能用，然后亲自跑了(ji��n)一�w�，发现不是我的�E�序有问题，是那边的��入个全角字符�Q�搜半角的字�W�，当然不行�?#8221;
恩，Betty写的需求真有意思，考虑的问题很周全�Q�是一个很厉害的项目经理。如果从输入�q�里解决�?ji��n)字�W�是否是半角的，那么�Q�以后的情况��容易解军_��多了(ji��n)。恩�Q�网上搜�?ji��n)一下资料，查了(ji��n)一下书�Q�得��Z��(ji��n)以下代码�Q?br />

public void testChar() {
  String s1 = "123";
  String s2 = "ａｂ�?/span>";
  String s3 = "123ａｂ�?/span>";
  System.out.println(s1);
  System.out.println(s2);
  System.out.println(s3);
  for (int i = 0; i < s1.length(); i++) {
   int j = s1.charAt(i);
   if (j > 256) {
    int temp = j - 65248;
    if (temp >= 0) {
     System.out.print((char)j+"-->:" + (char) temp);
    } else {
      System.out.print((char) j);
    }
   } else {
    System.out.print((char) j);
   }
  }
  System.out.println();

  for (int i = 0; i < s2.length(); i++) {
   int j = s2.charAt(i);
   if (j > 256) {
    int temp = j - 65248;
    if (temp >= 0) {
     System.out.print((char)j+"-->:" + (char) temp);
    } else {
     System.out.print((char) j);
    }
   } else {
    System.out.print ((char) j);
   }
  }
  System.out.println();

  for (int i = 0; i < s3.length(); i++) {
   int j = s3.charAt(i);
   if (j > 256) {
    int temp = j - 65248;
    if (temp >= 0) {
      System.out.print((char)j+"-->:" + (char) temp);
    } else {
     System.out.print((char) j);
    }
   } else {
    System.out.print((char) j);
   }
  }
  System.out.println();

}

输出的结果如下：(x��)

123
�?/span>-->a�?/span>-->b�?/span>--c
123�?/span>-->a�?/span>-->b�?/span>--c

wonderer 2007-12-23 16:46 发表评论

wonderer — Sat, 22 Dec 2007 16:52:00 GMT

OYM的�Q务中�Q�有个要求，上传一个Excel文�g�Q�检查他的内�Ҏ(gu��)��否合法，�q�返回信息�?/p>

今天想了(ji��n)一下，�W�一个要解决的问题就是上传一个Excel文�g�Q�上传文件的�l��g到挺多的�Q�网上一搜，��有一大堆教程�Q�但是现在�ƈ不是要上传一个文件到服务器以作存储之用，而是要上传一个文件到内存里，以Java的数据结构存储�v来，�q�检查，把合乎要求的数据写到数据库里。所以在�|�上的一大堆上传文�g的组件�ƈ不合用。于是又惌��己写�Q�思�\��是从客��L(f��ng)��那里获取一个InputStream�Q�然后就对这个InputStream做一�p�d��的检查。代码如下：(x��)

ServletInputStream sis =  request.getInputStream();
InputStreamReader isr = new InputStreamReader(sis);
             
int ch;
while((ch = isr.read()) != -1 ) {          
   out.println((char)ch);
}
             
System.out.flush();

�l�果的出��d��是如下（输出东西写到��面�Q�：(x��)

-----------------------------7d7ea23120550 
Content-Disposition: form-data; name="file1"; 
filename="C:\Documents and Settings\Administrator\桌面\test.txt" 
Content-Type: text/plain 
my name is Rokey.�QԌ��ｋｅｙ。我的名字叫Rokey. 
-----------------------------7d7ea23120550 Content-Disposition: form-data; 
name="Submit" 上传 -----------------------------7d7ea23120550--

很明显，�q�里只有

my name is Rokey.�QԌ��ｋｅｙ。我的名字叫Rokey.

�Ҏ(gu��)��有用�Q�这个也正是我的文�g里面的内容，其它的都是关于这些form的其它信息。对我这个程序是没有用的。如果这里写下去的话�Q�还要我��d��析那些是数据�Q�哪些是form的参数。好�Q�到现在为止�Q�我已经打消�?ji��n)自己写的念头�?ji��n)。我惻I��那些�l��g都可以把上传文�g��装得那么好�Q�能不能利用那些库，抽出文�g的IO��，让我操作�?

于是�Q�就开始对的API看，看到里面有这么一�D�c(di��n)�?/p>

public class MultipartParser
extends java.lang.Object
A utility class to handle multipart/form-data requests, the kind of requests that support file uploads. This class uses a "pull" model where the reading of incoming files and parameters is controlled by the client code, which allows incoming files to be stored into any OutputStream. If you wish to use an API which resembles HttpServletRequest, use the "push" model MultipartRequest instead. It's an easy-to-use wrapper around this class.
This class can receive arbitrarily large files (up to an artificial limit you can set), and fairly efficiently too. It cannot handle nested data (multipart content within multipart content). It can now with the latest release handle internationalized content (such as non Latin-1 filenames).
It also optionally includes enhanced buffering and Content-Length limitation. Buffering is only required if your servlet container is poorly implemented (many are, including Tomcat 3.2), but it is generally recommended because it will make a slow servlet container a lot faster, and will only make a fast servlet container a little slower. Content-Length limiting is usually only required if you find that your servlet is hanging trying to read the input stram from the POST, and it is similarly recommended because it only has a minimal impact on performance.

而且里面的API已经��装�E�我惌��得到的情况了(ji��n)。于是，我就觉得�q�样我就可以完成我的功能�?ji��n)。于是，��写�?ji��n)以下代码�?x��)

MultipartParser mp = new MultipartParser(request, 10 * 1024 * 1024);
Part part;
while ((part = mp.readNextPart()) != null) {
      if (part.isParam()) {
          // it's a parameter part
          ParamPart paramPart = (ParamPart) part;
          //out.println("param: name=" + name + "; value=" + value);
      } else if (part.isFile()) {
          FilePart filePart = (FilePart) part;
          InputStream is = filePart.getInputStream();
          InputStreamReader isr = new InputStreamReader(is);

          int ch;
          while ((ch = isr.read()) != -1) {

              out.print((char) ch);
          }

          System.out.flush();
          isr.close();
          is.close();
      }
}

出去�l�果如下�Q?/p>

my name is Rokey.�QԌ��ｋｅｙ�?
我的名字叫Rokey.

到现在，已经可以把这个流��装成一个文件流�Q�送给Excel的组件去处理�?ji��n)�?img src ="http://www.aygfsteel.com/wonderer/aggbug/169676.html" width = "1" height = "1" />

wonderer 2007-12-23 00:52 发表评论

转：(x��)什么是IOC

wonderer — Sun, 28 Oct 2007 08:50:00 GMT

摘要: 什么是IOC呢，在网上搜��C��(ji��n)一非常有意思的讲解。IoC��是Inversion of Control�Q�控制反转。在Java开发中�Q�IoC意味着��你设计好的�c�M��l�系�l�去控制�Q�而不是在你的�c�d��部控制。这�U�Cؓ(f��)控制反�{�?下面我们以几个例子来说明什么是IoC 假设我们要设计一个Girl和一个Boy�c�，其中Girl有kiss�Ҏ(gu��)��Q�即Girl惌��Kiss一个Boy。那么，我们的问题是�Q�Girl如何能够认识�q�个B... 阅读全文

wonderer 2007-10-28 16:50 发表评论

wonderer — Fri, 26 Oct 2007 08:41:00 GMT

Buffloa里的传递参数的�~�码是GBK�?/p>

buffalo.switchPart('body',url,false);如果url中包含汉字，是采用GBK�~�码的。在不改变tomcat的配�|�文件的情况下，在目标页面里获得url参数的正��方法是

   1: String name = new String(request.getParameter("name").getBytes(   2:             "ISO8859-1"), "GBK");

注意�Q�如果这里用utf-8作�ؓ(f��)�~�码的�{换的话，�?x��)出��Cؕ码�?/p>

wonderer 2007-10-26 16:41 发表评论

JSP中request.getParameter()��q��问题

wonderer — Thu, 25 Oct 2007 15:23:00 GMT

最�q�在准备考试�pȝ��的开发，��到�?request.getParameter��q��的问题。跟林�{讨论�?ji��n)一下，�q�是觉得用老方法管用�?/p>

如果是post的话�Q�可以通过讄��filter的方法来解决�?/p>

如果是get或者是��链接的话，以前是通过讄��tomcat的配�|�文件server.xml来解决的�Q�但�q�样不好�Q��ƈ不是所有的��目�Q�我们都可以修改到服务器的tomcat的配�|�文件。具体代码如下：(x��)

   1: Connector port="8080" maxHttpHeaderSize="8192"   2:                maxThreads="150" minSpareThreads="25" maxSpareThreads="75"   3:                enableLookups="false" redirectPort="8443" acceptCount="100"   4:                connectionTimeout="20000" disableUploadTimeout="true" uRIEncoding="gbk"/>

�q�是觉得老方法管用，只是有点�ȝ��(ch��):

   1: String id=new String(request.getParameter("id").getBytes("ISO8859-1"),"UTF-8");   2: String name = new String(request.getParameter("name").getBytes("ISO8859-1"),"UTF-8");

wonderer 2007-10-25 23:23 发表评论

讄��ip的bat

wonderer — Tue, 11 Sep 2007 09:25:00 GMT

�?sh��)脑搬回了(ji��n)宿舍，破解了(ji��n)校园网�Q�多人公用一条宽带。要一个主机拨受��ip��M��免要设来讑֎��Q��L��要手工改�Q�很�ȝ��(ch��)�Q�于是上�|�查�?ji��n)查�Q�写�?ji��n)个改ip的bat文�g。内容如下：(x��)

   1: netsh interface ip set address name="本地�q�接" source=static addr=192.168.0.39
            mask=255.255.255.0 gateway=192.168.0.1 gwmetric=1
   2: netsh interface ip set dns name = "本地�q�接" source = static addr = 202.116.128.1   3: netsh interface ip add dns name = "本地�q�接" addr = 202.116.128.2

wonderer 2007-09-11 17:25 发表评论

html中TD标签的一个小问题

wonderer — Fri, 03 Aug 2007 02:32:00 GMT

在写HTML中，�q�不�?amp;nbsp才会(x��)产生一个空根{�?lt;td>hello (间隔一个空�?输出的数据是�Q?hello+一个空�?如果是对�q�数据进行修改然后再写回到数据库的话�Q�这样就�?x��)��生错误�?/p>

如下写法是会(x��)错误的，

造成的结果是仔细留意�?x��)发现运通后面多�?ji��n)一个空�?/p>

必须�Ҏ(gu��)��一下写法：(x��)

注意跟前面是没有�I�格的。这栯��行结果就�?x��)是�q�样�?a href="http://www.aygfsteel.com/images/blogjava_net/wonderer/WindowsLiveWriter/htmlTD_92F0/image_3.png" atomicselection="true"> �Q�是没有�I�格的�?/p>

wonderer 2007-08-03 10:32 发表评论

Spring DAO入门

wonderer — Wed, 18 Jul 2007 06:04:00 GMT

摘要: 写了(ji��n)个Spring的DAO入门例子�?DAO的接�? 1: package dataSourceDemo; 2: 3: public interface IUserDAO { 4: public void insert(User user); 5: public User find(Integer id); 6: 7: } ... 阅读全文

wonderer 2007-07-18 14:04 发表评论

JUnit+Spring入门

wonderer — Wed, 18 Jul 2007 03:12:00 GMT

首先要导入包

1�Q�Spring支持包：(x��)spring.jar , commons-logging.jar

2: JUnit支持包：(x��) JUnit.jar

建立Bean�c�，

   1: package refBeanDemo;   2:     3: import java.util.Date;   4:     5: public class HelloBean {   6:     private String helloWorld;   7:     private Date date;   8:     public Date getDate() {   9:         return date;  10:     }  11:     public void setDate(Date date) {  12:         this.date = date;  13:     }  14:     public String getHelloWorld() {  15:         return helloWorld;  16:     }  17:     public void setHelloWorld(String helloWorld) {  18:         this.helloWorld = helloWorld;  19:     }  20:       21: }

建立配置文�g�Q�和在里面进行注�?/p>

   1: xml version="1.0" encoding="UTF-8"?>   2: DOCTYPE beans PUBLIC "-//SPRING/DTD BEAN/EN" "../resources/spring-beans-2.0.dtd" >   3: <beans>   4:     <bean id="dateBean" class="java.util.Date">bean>   5:        6:     <bean id="helloBean" class="refBeanDemo.HelloBean">   7:         <property name="helloWorld">   8:             <value>你好�Q�世�?span style="color: #0000ff">value>   9:         property>  10:         <property name="date" ref="dateBean">property>  11:     bean>  12: beans>

写JUnit�q�行��试�Q�方便管理，把JUnit的东东放到test包里�?/p>

   1: package refBeanDemo;   2:     3: import org.springframework.context.ApplicationContext;   4: import org.springframework.context.support.ClassPathXmlApplicationContext;   5:     6: import junit.framework.TestCase;   7:     8: public class TestRefBeanDemo extends TestCase {   9:     private ApplicationContext context;  10:    11:     public void setUp() {  12:         context = new ClassPathXmlApplicationContext("refBeanDemo/NewFile.xml");  13:     }  14:    15:     public void testSpring() {  16:         HelloBean helloBean = (HelloBean)context.getBean("helloBean");  17:         System.out.println(helloBean.getDate());  18:         assertEquals("你好�Q�世�?, helloBean.getHelloWorld());  19:           20:     }  21: }

�q�行JUnit��试

��试成功。类的分布如下：(x��)

wonderer 2007-07-18 11:12 发表评论