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Java只能处理300个异常？

FinalFantasy — Thu, 29 Dec 2005 10:21:00 GMT

首先看看我写的一个小�E�序�Q?BR>
public class TestTry extends Exception
{
static boolean f=false;
static int sum=0;
static int created=0;
static int i=0;
TestTry()
{
  i=created++;
  if(created>=299) f=true;
  }
public void finalize()
{
  sum++;
  }
public static void main(String[] args)
{
  while(!TestTry.f)
  {
   try{
    throw new TestTry();
    }catch(Exception e){}
    finally{
     System.out.println("Creat "+TestTry.i+" TestTry, "+TestTry.sum+" has been finalized!");
     }
    }
  //System.out.println("Creat "+TestTry.created+" TestTry, "+TestTry.sum+" has been finalized!");
  }
}

�q�个是我在测试在try语句抛出异常后，在try语句中徏立的对象是否会调用自�w�的�l�止函数时发现的�Q�这里有个奇怪的现象在if(created>=299) f=true;�q�条语句中，如果把条件created>=299改�ؓ>=�?99更大的数�Q�你会发现System.out.println("Creat "+TestTry.i+" TestTry, "+TestTry.sum+" has been finalized!");�q�条语句的输出的�l�果�q�不是你预想的那��P��输出判断的数�?1的行敎ͼ��Q�而只是显�C�最后的三百行。那么在�q�之前抛出的异常上哪里去了呢�Q�难道说Java只处理最后抛出的三百的异�怹��Q?BR>

FinalFantasy 2005-12-29 18:21 发表评论

FinalFantasy — Wed, 21 Dec 2005 10:24:00 GMT

Problem Statement

You are given a String[] cityMap representing the layout of a city. The city consists of blocks. The first element of cityMap represents the first row of blocks, etc. A 'B' character indicates a location where there is a bus stop. There will be exactly one 'X' character, indicating your location. All other characters will be '.'. You are also given an int walkingDistance, which is the maximum distance you are willing to walk to a bus stop. The distance should be calculated as the number of blocks vertically plus the number of blocks horizontally. Return the number of bus stops that are within walking distance of your current location.

Definition

Class:BusStops
Method:countStops
Parameters:String[], int
Returns:int
Method signature:int countStops(String[] cityMap, int walkingDistance)
(be sure your method is public)

Constraints

-cityMap will contain between 1 and 50 elements, inclusive.
-Each element of cityMap will contain between 1 and 50 characters, inclusive.
-Each element of cityMap will contain the same number of characters.
-Each character of each element of cityMap will be 'B', 'X', or '.'.
-There will be exactly one 'X' character in cityMap.
-walkingDistance will be between 1 and 100, inclusive.

Examples

0)

{"...B.",
".....",
"..X.B",
".....",
"B...."}
3
Returns: 2
You can reach the bus stop at the top (3 units away), or on the right (2 units away). The one in the lower left is 4 units away, which is too far.

1)

{"B.B..",
".....",
"B....",
".....",
"....X"}
8
Returns: 3
A distance of 8 can get us anywhere on the map, so we can reach all 3 bus stops.

2)

{"BBBBB",
"BB.BB",
"B.X.B",
"BB.BB",
"BBBBB"}
1
Returns: 0
Plenty of bus stops, but unfortunately we cannot reach any of them.

3)

{"B..B..",
".B...B",
"..B...",
"..B.X.",
"B.B.B.",
".B.B.B"}
3
Returns: 7

说实话我觉得�q�一题没啥意思，��简单，首先先确定X的位�|�，再用遍历数组找B的位�|�，再求相减的绝对值然后判断是否超出给出的最大距��d��行了。相对这题PlayCars却很有意思，到现在我也没惛_��除了�I��D以外的一个更好的��法�Q�因为我觉得�I��D可能会超时。有哪位有其它的办法的话�Q�请告诉我，大家探讨一下，谢谢。好了，不废话了�Q�下面是�q�题的答案：

public class BusStops {
public static void main(String[] arg){
  BusStops total = new BusStops();

    System.out.println(total.countStops({"...B.",".....","..X.B",".....","B...."},3));
}

public int countStops(String[] cityMap, int walkingDistance){
  int sum= 0;
  int locationX = -1;
  int locationY = -1;
  for(int i=0;i   for(int j=0;j    if(cityMap[i].charAt(j)=='X'){
     locationX = i;
     locationY = j;
    }
   }
  }
  for(int i=0;i   for(int j=0;j    if(cityMap[i].charAt(j)=='B' && (Math.abs(locationX - i) + Math.abs(locationY - j)<=walkingDistance))
     sum++;
   }
  }
  return sum;
}
}

FinalFantasy 2005-12-21 18:24 发表评论

FinalFantasy — Tue, 01 Nov 2005 05:05:00 GMT

《thinking in java》中一�D�代码剖�?/FONT>

�E�序代码

//chapter03:Garbage.java

// Demonstration of the garbage

// collector and finalization

class Chair {

static boolean gcrun = false;

static boolean f = false;

static int created = 0;

static int finalized = 0;

int i;

Chair() {

i = ++created;

if(created == 47)

System.out.println("Created 47");

}

public void finalize() {

if(!gcrun) {

// The first time finalize() is called:

gcrun = true;

System.out.println(

"Beginning to finalize after " +

created + " Chairs have been created");

}

if(i == 47) {

System.out.println(

"Finalizing Chair #47, " +

"Setting flag to stop Chair creation");

f = true;

}

finalized++;

if(finalized >= created)

System.out.println(

"All " + finalized + " finalized");

}

public class Garbage {

public static void main(String[] args) {

// As long as the flag hasn't been set,

// make Chairs and Strings:

while(!Chair.f) {

new Chair();

new String("To take up space");

}

System.out.println(

"After all Chairs have been created:\n" +

"total created = " + Chair.created +

", total finalized = " + Chair.finalized);

// Optional arguments force garbage

// collection & finalization:

if(args.length > 0) {

if(args[0].equals("gc") &line;&line;

args[0].equals("all")) {

System.out.println("gc():");

System.gc();

}

if(args[0].equals("finalize") &line;&line;

args[0].equals("all")) {

System.out.println("runFinalization():");

System.runFinalization();

}

System.out.println("bye!");

}

} ///:~��Z��么执�?SPAN lang=EN-US style="COLOR: red">java Garbage gc以后�Q�当所有对象创建完�Q�比�?SPAN lang=EN-US>8000个）�Q�这时只清除�?SPAN lang=EN-US>2000个（不定�Q�，应该只能创徏47个对象啊

分析�Q?/FONT>

首先�Q�在一个��@环当中创建对象，�q�且只是创徏�Q�而不引用�Q�也��是说这个对象会自动的被�pȝ��当作垃圾处理掉。但��h��意，finalize()�Ҏ��q�不是立��d��会执行的�Q�执行的旉��完全��q��l�来军_��。所以很有可能的情况是已�l�创��Z��20000个对象，才开始其中的某一个对象的清除工作�Q�这可能和时间或者系�l�内容的占用有关�Q�。看finalize()�Ҏ��中的一�D�代码：

if (!gcrun) {

gcrun = true;

System.out.println(

"\nBeginning to finalize after" + created + "Chairs have been created\nat ");

}

��׃��出现�q�样的结果：

Beginning to finalize after 25038 Chairs have been created

�q�时对象的创��E�仍在��l�（因�ؓ已经Finalize的对象还不满47个，Chair.f�q�是false�Q�。所�?SPAN lang=EN-US>Chair.created会��l�增加�?/FONT>

直到�?SPAN lang=EN-US>47个对象被清除了，Chair.f被置�?SPAN lang=EN-US>true了，创徏对象的��@环才�l�束。看main�Ҏ��中的一�D�代码：

System.out.println(

"\nAfter all chairs have been created:\n"

+ "total created ="

+ Chair.created

+ ",total finalized ="

+ Chair.finalized+"\n");

如上所��_��Chair.created是不断增加的�Q�而在�q�段代码执行之前�Q�又会有N个对象被释放掉了�Q�所�?SPAN lang=EN-US>finalized也增加了�?/FONT>

�l�果可能是这��L��Q?/FONT>

total created =29096,total finalized =73

其实�q�一�q�程和��用的JVM有很大关�p�，执行�l�果可能会很不相同。但有一�Ҏ��可以肯定的，那就�?SPAN style="COLOR: red">我们无法��定JVM什么时候做对象的清除工�?/SPAN>�Q�这也是Thinking in java中这�D�代码的惌��说明的）�Q?SPAN style="COLOR: red">可能会在�q�个对象刚刚�?/SPAN>无用�?/SPAN>的时候就清除掉了�Q�也可能滞后几秒�Q�甚��x��q�不清除�?/SPAN>

�l�论�Q?/FONT>

不能指望finalize()�Ҏ��能稳定的工作�Q�尤其不能依靠它来做文�g的关闭等操作�Q�由�?SPAN lang=EN-US>finalize()的不��定性，往往得不��C��惌��的结果。事实上我们只需要知道所有无用的对象�Q?SPAN lang=EN-US>JVM会自己清除就够了。省点心思去睡觉岂不是更好的一件事�?�Q�）

FinalFantasy 2005-11-01 13:05 发表评论

FinalFantasy — Thu, 06 Oct 2005 11:28:00 GMT

�z�阳的天气可真是讨厌�Q�昨天好不容易放晴了一天，今天��又下�v了大雨，本来计划好去买衣服的�Q�现在只能��汤了。这几天来上�|�查了很多的资料�Q��ؓ了组��Z��个PHP、JSP、ASP的全能��^収ͼ�PHP跟JSP的��^台是�l�徏好了�Q�可是ASP怎么样都不行�Q�好不容易下了个IASP装上了，配置了之后却老是出现错误。哎NB怎么��׃��配个专业版的�pȝ��l�我呢，�q�样我就不用那么费劲了，只要把IIS跟Apache整合��h��p��了。趁着有点旉��把用apache�l�徏的PHP、JSP�q�_��教程整理出来了，说实话光�q�两个都费了我好多的劲呀�Q�特别是JSP�Q�网上的教程都不知道是什么年代写的了�Q�几乎都不能用了�Q�我废了好几天的功夫才把�q�些零�g�l�找齐，所以还特别��C��了下载的地址�Q�要下的��p��赶快了！好了�Q�废话不多说了，往下看吧。对了，另外再多说一句，下面的配�|�是我安装我本机的安装地址的，如果你的安装地址跟我的不�W�，那么你就要一些相应的改进�Q�还有，如果一下的下蝲地址无效了，你可以在我这留下你的邮箱�Q�我可以��这些东西发�l�你�?BR>

前期准备�Q?nbsp;

所需软�g列表
1、apache_2.0.54-win32-x86-no_ssl.exe �Q�Apache web服务器） http://apache.justdn.org/......2.0.54-win32-x86-no_ssl.exe
2、php-5.0.5-Win32 �Q�PHP语言解析器）
4、jdk1.4.2�Q�JAVA 语言环境�Q?
5、jakarta-tomcat-5.5.12 �Q�Tomcat JSP解析服务器） http://mirror.vmmatrix.ne......in/apache-tomcat-5.5.12.exe
7、mod_jk-1.2.14-apache-2.0.54.so.asc �Q�整合Apache+Tomcat的plus�Q?http://apache.linuxforum.......1.2.14-apache-2.0.54.so.asc�Q��ؓ了找�q�个文�g都把我给扄��了，�|�上的教�E�到处都说要mod_jk_1.2.5_2.0.47.dll�Q�可是我找了两天死都找不刎ͼ�后来到apache的官方网站看着生硬的EN��L��才找到这么个文�g�Q�看文�g名直觉就告诉我找对了�Q�现在的apache不都是用so扩展了么�Q�而且在那个页面也说明了这一点，要��用还要改名，所以在�q�里特别指出下蝲地址�Q�让大家��走很多的弯路）

开始安装：
一�?Apahce+PHP安装配置

1、安装apache_2.0.54-win32-x86-no_ssl.exe�Q��ؓ了方便把路径改�ؓc:\吧，其他都不用管一路next下去�?
2、安装完成之后，apache服务自动加蝲�Q�这时打开��览器，��览�Q?A href="http://localhost/">http://localhost�Q�出现apache�Ƣ迎��面�Q�这步需要将C:\apache2\htdocs目录中的文�g“index.html.en”改为“index.html”，方能昄��Q�；如果�q�步出现异常�Q�请��查安装源文�g�Q�重新安装�?
3. 安装php-5.0.5-Win32,一般下载的PHP文�g��Z��个免安装的压�~�包�Q�解压到C�Q�\PHP��可以�?nbsp;
4. 配置PHP和Apache�Q��之能解析php�E�序�?nbsp;
PHP配置�Q�将C:\PHP\目录中的“php.ini-dist”改名“php.ini�?然后��d��环境变量。在环境变量里的classpath中添加�?;c:\php;”，在新��Z��个“PHPRC”的变量�Q�里面同��h��d��?;c:\php;�?nbsp;
Apache配置�Q?nbsp;
打开C:\apache2\conf\httpd.conf

httpd.conf是apache的配�|�文�Ӟ��在此配置文�g最后添加以下语句，用以支持php�E�序�Q?nbsp;

ScriptAlias /php/ "C:/PHP/"

AddType application/x-httpd-php .php3

AddType application/x-httpd-php .php

AddType application/x-httpd-php .phtml

Action application/x-httpd-php "/php/php.exe"

ok�Q�接下来重启Apache服务器（如果加蝲PHP成功�Q�可以在Apache监控器中看到Apache/2.0.52(win32) PHP/5.0.4�Q�就可以��试了PHP了，用编辑器�~�写如下语句�Q?nbsp;
phpinfo();

保存文�g名�ؓ“test.php”到C:\apache2\htdocs目录�Q�然后打开��览器，��览�Q?A href="http://localhost/test.php">http://localhost/test.php�Q�出现PHP基本信息��p��明配�|�成功。严格按以上说明安装配置�Q�都会一�ơ成功�?

二、安装JDK和Tomcat

1. 安装j2sdk-1_4_2-windows-i586�Q�JDK一定要在Tomcat之前安装�Q�默认安装�\径就可以�?BR>2. 安装Jakarta-Tomcat-5.5.12�Q�默认安装�\径就可以�?BR>4�Q�设�|�环境变量（桌面->我的电脑->右键点击->选择“属性�?>高��->环境变量�Q�，所有设�|�均在系�l�变量栏�q�行�?BR>新徏->变量名：JAVA_HOME
->变量��|��C:\j2sdk1.4.2
新徏->变量名：TOMCAT_HOME
->变量��|��C:\Program Files\Apache Software Foundation\Tomcat 5.5
新徏->变量名： PATH
->变量��|��.;C:\j2sdk1.4.2\bin; �Q�前面的�?;”一定要有）
修改增加环境变量 CLASSPATH (如果没有此变量名�Q�则新徏)
->增加变量��|��.;C:\j2sdk1.4.2\lib\dt.jar;C:\j2sdk1.4.2\lib\tool.jar;
C:\j2sdk1.4.2\lib\NetComponents.jar;
C:\Program Files\Apache Software Foundation\Tomcat 5.5\common\classes;
C:\Program Files\Apache Software Foundation\Tomcat 5.5\common\lib;
C:\Program Files\Apache Software Foundation\Tomcat 5.5\common\lib\servlet-api.jar;�Q�前面的�?;”一定要有）

5. 启动Tomcat服务器，打开��览器，��览�Q?A href="http://localhost:8080/">http://localhost:8080/ �Q�出现Tomcat�Ƣ迎��面�Q�如果这步出现异常，��h��查安装源文�g�Q�重新安装�?/P>

三、整合Apache+Tomcat服务�?/P>

1. 复制mod_jk-1.2.14-apache-2.0.54.so.asc文�g到C:\Apache2\modules目录�Q��ƈ��其文�g名改为mod_jk.so�?BR>2. Apache配置�Q?BR>C:\apahce2\conf\httpd.conf
httpd.conf
在此配置文�g最后添加以下语句，用以支持jsp�E�序�Q?BR>LoadModule jk_module modules/mod_jk.so

JkWorkersFile "C:/Program Files/Apache Software Foundation/Tomcat 5.5/conf/workers.properties"
JkMount /servlet/* ajp13
JkMount /*.jsp ajp13

�q�有要在
DirectoryIndex index.html index.html.var的后面加上default.jsp index.jsp�Q�前面忘了说了，支持PHP�q�要加上index.php default.php�Q?/P>

3. 在C:\Program Files\Apache Software Foundation\Tomcat 5.5\conf\目录下，新徏文�g名�ؓ“workers.properties”的文�g�Q�将如下内容复制到新建文件workers.properties中�?/P>

workers.properties
# 只复制以下内容即可：

workers.tomcat_home=C:\Program Files\Apache Software Foundation\Tomcat 5.5
workers.java_home=C:\j2sdk1.4.2
ps=\
# worker.list=ajp13
worker.list=ajp12,ajp13

worker.ajp12.port=8007
worker.ajp12.host=localhost
worker.ajp12.type=ajp12
worker.ajp12.lbfactor=1

worker.ajp13.port=8009
worker.ajp13.host=localhost
worker.ajp13.type=ajp13
worker.ajp13.lbfactor=1

worker.loadbalancer.type=lb

worker.loadbalancer.balanced_workers=ajp12, ajp13
worker.inprocess.type=jni
worker.inprocess.class_path=$(workers.tomcat_home)$(ps)classes
worker.inprocess.class_path=$(workers.tomcat_home)$(ps)lib$(ps)jaxp.jar

worker.inprocess.class_path=$(workers.tomcat_home)$(ps)lib$(ps)parser.jar

worker.inprocess.class_path=$(workers.tomcat_home)$(ps)common$(ps)lib$(ps)jasper.jar

worker.inprocess.class_path=$(workers.tomcat_home)$(ps)common$(ps)lib$(ps)servlet.jar

worker.inprocess.class_path=$(workers.tomcat_home)$(ps)common$(ps)lib$(ps)webserver.jar

worker.inprocess.class_path=$(workers.java_home)$(ps)lib$(ps)tools.jar

worker.inprocess.cmd_line=-config

worker.inprocess.cmd_line=$(workers.tomcat_home)/conf/jni_server.xml

worker.inprocess.cmd_line=-home

worker.inprocess.cmd_line=$(workers.tomcat_home)

worker.inprocess.jvm_lib=$(workers.java_home)$(ps)jre$(ps)bin$(ps)classic$(ps)jvm.dll

worker.inprocess.stdout=$(workers.tomcat_home)$(ps)inprocess.stdout

worker.inprocess.stderr=$(workers.tomcat_home)$(ps)inprocess.stderr

worker.inprocess.sysprops=tomcat.home=$(workers.tomcat_home)

接下来重启Tomcat和Apache服务器（必须先重启Tomcat再重启Apache�Q�不然会出错�Q�如果加载JK成功�Q�这个时候你可以在Apache监控器中看到Apache/2.0.52(win32) PHP/5.0.4 mod_jk/1.2.8�Q�就可以��试了，把Tomcat的webapps�q�个目录拯��到Apache的htdocs目录下面�Q�然后直接在��览器地址栏输入：http://localhost/webapps �?http://localhost:8080如果昄��的页面一样就说明成功了�?/P>

剩下的就是连接MySQL了，但是本�h不才一个叫mm.mysql-2.0.4-bin.jar的文件怎么也找不到�Q�只扑ֈ�了个mysql-connector-java-3.1.5-gamma-bin.jar的文�Ӟ��可是我试�q�了一点用都没有，所以连接数据库的教�E�等我试验成功再说拉�Q�如果哪位高��救救我的告诉我mm.mysql-2.0.4-bin.jar的下载地址或者告诉我IASP到底改如何配�|�，我真是感�Ȁ不尽�?BR>

FinalFantasy 2005-10-06 19:28 发表评论