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实现一个栈,使其push,pop,min(取得栈中的最��元�?均�ؓO(1)

Job Hu — Wed, 18 Jul 2007 12:57:00 GMT

实现一个栈,使其push,pop,min(取得栈中的最��元�?均�ؓO(1)

我的�?br>

interface IntStack
{
    int pop();
    void push(int i);
    int get();
}

class MinStack
{
    //store all the element
    private IntStack elemStack = new IntStack();

    //store current and historical smallest element
    private IntStack minStack = new IntStack();

    public void push(int i)
    {
        elemStack.push(i);

        int currentMin = minStack.get();
        if(i <= currentMin) minStack.push(i);
    }

    public int pop()
    {
        int result = elemStack.pop();
        if(result == minStack.get()) minStack.pop();
        return result;
    }

    public int getMinElem()
    {
        return minStack.get();
    }
}

Job Hu 2007-07-18 20:57 发表评论

Job Hu — Wed, 18 Jul 2007 12:37:00 GMT

把一个二叉排序树(也许不叫�q�个)变�ؓ递增的双向链�?不能够生成额外的�l�点.
eg 6
       / \
      4   8
     / \ / \
    3 5 7 9

3=4=5=6=7=8=9

我的�?

class Node
{
    public Node left;
    public Node right;

    private static Node getLinkListTail(Node head)
    {
        Node result = head;
        if(result==null) return null;
        while(result.right!=null)
        {
            result = result.right;
        }
        return result;
    }

    public static Node flatten(Node root)
    {
        if(root==null) return null;

        Node result = root;

        // A leaf node
        if(root.left==null&&root.right==null) return root;

        //divide-and-conquer
        Node leftSubTreeLinkListHead = flatten(root.left);
        Node rightSubTreeLinkListHead = flatten(root.right);

        //merge
        Node leftSubTreeLinkListTail = getLinkListTail(leftSubTreeLinkListHead);
        root.left = leftSubTreeLinkListTail;
        root.right = rightSubTreeLinkListHead;
        if(leftSubTreeLinkListHead!=null)
        {
            result = leftSubTreeLinkListHead;
            leftSubTreeLinkListTail.right = root;
        }
        if(rightSubTreeLinkListHead!=null) rightSubTreeLinkListHead.left = root;

        return result;
    }
}

Job Hu 2007-07-18 20:37 发表评论

Byte in Java

Job Hu — Tue, 17 Jul 2007 15:22:00 GMT

public class ByteTest
{
    public static void main(String[] args)
    {
        byte b;
        byte c;
        //b = 255; //Cannot convert from int to byte
        //b = 0xFF; //Cannot convert from int to byte
        b = 127;
        c = 0x7F;
        if(b == c) System.out.println("b == c");
        if(127 == 0x7F) System.out.println("127 == 0x7F");

        b = -128;
        //c = 0x80; //Cannot convert from int to byte
        c = (byte)0x80;
        if(b == c) System.out.println("b == c");
        if(-128 == 0x80) System.out.println("-128 == 0x80");
        if(128 == 0x80) System.out.println("128 == 0x80");

        c = (byte)0x80;
        if(128 == c) System.out.println("128 == c");
        if(-128 == c) System.out.println("-128 == c");
        if(128 == (c&0xFF)) System.out.println("128 == (c&0xFF)");
    }
}

输出:
b == c
127 == 0x7F
b == c
128 == 0x80
-128 == c
128 == (c&0xFF)

Job Hu 2007-07-17 23:22 发表评论

Java Language Keywords

Job Hu — Mon, 09 Jul 2007 14:38:00 GMT

Here's a list of keywords in the Java programming language. You cannot use any of the following as identifiers in your programs. The keywords const and goto are reserved, even though they are not currently used. true, false, and null might seem like keywords, but they are actually literals; you cannot use them as identifiers in your programs.

`abstract`	`continue`	`for`	`new`	`switch`
`assert`^***	`default`	`goto`^*	`package`	`synchronized`
`boolean`	`do`	`if`	`private`	`this`
`break`	`double`	`implements`	`protected`	`throw`
`byte`	`else`	`import`	`public`	`throws`
`case`	`enum`^****	`instanceof`	`return`	`transient`
`catch`	`extends`	`int`	`short`	`try`
`char`	`final`	`interface`	`static`	`void`
`class`	`finally`	`long`	`strictfp`^**	`volatile`
`const`^*	`float`	`native`	`super`	`while`

Job Hu 2007-07-09 22:38 发表评论

Job Hu — Wed, 30 May 2007 14:58:00 GMT

来看�?/span>ContainerBase�?/span>start�Ҏ��Q?br>

1public synchronized void start() throws LifecycleException {
2
3        //如果Container已经处于start状态，直接�q�回
4        if (started) {
5            if(log.isInfoEnabled())
6                log.info(sm.getString("containerBase.alreadyStarted", logName()));
7            return;
8        }
9
10        // Notify our interested LifecycleListeners
11        lifecycle.fireLifecycleEvent(BEFORE_START_EVENT, null);
12
13        started = true;
14
15        // Start our subordinate components, if any
16        if ((loader != null) && (loader instanceof Lifecycle))
17            ((Lifecycle) loader).start();
18        logger = null;
19        getLogger();
20        if ((logger != null) && (logger instanceof Lifecycle))
21            ((Lifecycle) logger).start();
22    //用来��理session
23        if ((manager != null) && (manager instanceof Lifecycle))
24            ((Lifecycle) manager).start();
25    //看名字就知道是干什么的�Q�不�q�研�I��的优先�U�很�?/span>
26        if ((cluster != null) && (cluster instanceof Lifecycle))
27            ((Lifecycle) cluster).start();
28    //用来�q�行讉K��控制�Q�或者权限控制的
29        if ((realm != null) && (realm instanceof Lifecycle))
30            ((Lifecycle) realm).start();
31    //和JNDI相关
32        if ((resources != null) && (resources instanceof Lifecycle))
33            ((Lifecycle) resources).start();
34
35        //启动所有子container
36        Container children[] = findChildren();
37        for (int i = 0; i < children.length; i++) {
38            if (children[i] instanceof Lifecycle)
39                ((Lifecycle) children[i]).start();
40        }
41
42        // 启动Container内部持有的pipeline对象�Q�Container对Pipeline接口的实现就是通过调用�q�个内部持有的Pipeline对象
43        if (pipeline instanceof Lifecycle)
44            ((Lifecycle) pipeline).start();
45
46        // Notify our interested LifecycleListeners
47        lifecycle.fireLifecycleEvent(START_EVENT, null);
48
49        // 注释说这个函数用来check session是否�q�期�Q�但看的不是太懂
50        threadStart();
51
52        // Notify our interested LifecycleListeners
53        lifecycle.fireLifecycleEvent(AFTER_START_EVENT, null);
54
55}
56

所有和cluster�?/span>realm相关都放在最后来研究了，不管怎么样先�?/span>tomcat如何处理request的整个过�E�串��h��对现在的我来说是最重要的。另外还�?/span>Tomcat中的很多部�g都用��C��JMX API�Q�即SNMP�?/span>Java实现来进行性能��和��理�Q�这个也会放在最后研�I��?/span>

ContainerBase��q��q�么多了�Q�下面来看看StandardEngine�q�个�c�R��除��d��cluster�?/span>realm�?/span>JMX相关的方法后�Q?/span>StanderdEngine剩下的方法就很很��了�?/span>

StandardEngine有一�?/span>Service�c�d��的成员�?/span>Java doc中指�?/span>Service��是由很多共享同一�?/span>Container�?/span>Connector�l�成。一�?/span>Service对应于一�?/span>Container�Q�来自这�?/span>Service的�Q何一�?/span>Connector�?/span>request都会由其对应�?/span>Container�q�行处理。看到现在的感觉��是Connector�?/span>Container提供request对象�Q��ƈ接受Container�q�回�?/span>response对象。在Tomcat中有很多�c�d��都被用来体现�?/span>request或�?/span>response�Q�例�?/span>org.apache.catalina.connector .Request��是Coyote request的一�?/span>wrapper�c�，Coyote�q�个framework帮助��装了底层的�|�络复杂性，向上提供一个统一的接口。我�?/span>tomcat既能够成��Z��?/span>standalone�?/span>http�?/span>jsp/Servlet服务器，也能够同apache http server集成�Q�很可能��是依赖�?/span>Coyote提供的统一接口�?/span>

在构造函��C��会将StandardEngine�q�个Pipeline的最后一�?/span>Valve�Q�即Basic讄��?/span>StandardEngineValve。来看看StandardEnginValue�?/span>invoke�Ҏ��

1public final void invoke(Request request, Response response)
2        throws IOException, ServletException {
3
4        // Select the Host to be used for this Request
5        Host host = request.getHost();
6        if (host == null) {
7            response.sendError
8                (HttpServletResponse.SC_BAD_REQUEST,
9                 sm.getString("standardEngine.noHost",
10                              request.getServerName()));
11            return;
12        }
13
14        // Ask this Host to process this request
15        host.getPipeline().getFirst().invoke(request, response);
16
17    }
18

可以看出在处理到StandardEngine�q�个Pipeline的最后一�?/span>Valve�Ӟ��会根据当�?/span>request所指定�?/span>Host�Q�将当前�?/span>request�?/span>response传递给�?/span>Host�q�个Pipeline的第一�?/span>Valve�q�行处理�?/span>

我想Tomcat中的Engine�?/span>Host�?/span>Context�?/span>Wrapper处理request生成response的过�E�大概是�q�样的：

Engine在收�?/span>request后在�?/span>Pipeline中的每一�?/span>Valve�?/span>request�q�行处理�Q�也可能会生�?/span>response的某些部分，在最后一�?/span>Valve中将request�?/span>response传给下一�U?/span>Container�?/span>Host的第一�?/span>Valve�?/span>Host重复同样�q�程�Q��l�传递给Context�Q?/span>Context再传递给Wrapper。由�?/span>Wrapper代表的是Servlet对象�Q�因此在Wrapper处所有的处理都结束了�Q?/span>response对象生成完毕。当然了�Q�如果在某一�U�中无法扑ֈ�request要求的下一�U�对象，则整个处理过�E�也会立即结束�?/span>

Job Hu 2007-05-30 22:58 发表评论

Job Hu — Sun, 27 May 2007 23:39:00 GMT

ContainerBase�?/span>Pipeline接口的实现完全依赖于其内部的一�?/span>Pipeline�c�d��的成�?/span>pipeline�Q�实现类�?/span>StandardPipeline�Q��?br> �?/span>Tomcat�?/span>doc中这样介�l?/span>Pipeline接口�Q�该接口�?/span>invoke�Q�）�Ҏ��被调用时�Q�将会引发一�p�d��Value对象的序列调用。要求一�?/span>Pipeline中的存在一�?/span>Value对象�Q�多为最后一�?/span>Value对象�Q�完成对request的处理，�q�生成相应的response�Q�而不能试囑ְ�Request�l�箋传递给其它Value对象�Q�这�?/span>Value对象被称�?/span>Basic�Q�。通常�Q�每�?/span>Container对象都持有一�?/span>Pipline�c�d��(实际上�ؓStandardPipeline)的成员。在Pipeline�?/span>doc中，�Ҏ��getBasic�Q?/span>getFirst两个�Ҏ��?/span>Method Summary完全一��P��Apache的牛��Z��也不能免俗啊�?/span>

StandardPipeline除实�?/span>Pipeline接口外，也实��C��Lifecycle接口。这个类�?/span>start�?/span>stop�Ҏ��Q�首先检查是否已�l�被start�?/span>stop�Q�如果是则会抛出一�?/span>LifecycleException的异常，否则�?/span>fire和生命期改变的相关事�Ӟ��q�调用其内部valve对象�Q�如果该valve对象也实��C��Lifecycle接口�Q�的start�?/span>stop�Ҏ��?/span>addValve�Ҏ��用来�?/span>StandardPipeline中加�?/span>Valve对象�Q�新加入�?/span>Value对象被放在一个叫�?/span>Basic的特�D?/span>Valve�Q�就是一�?/span>Pipeline的最后一�?/span>Valve�Q�的前面�Q�如果在��d��Valve的时候该StandardPipeline已经处于start状态，则会�q�行一些注册（调用apache commons库的一个类�Q�完全没有看懂这个地�Ҏ��什么作�?/span>>_<�Q?/span>

Job Hu 2007-05-28 07:39 发表评论

Job Hu — Tue, 15 May 2007 04:53:00 GMT

//以前写在blogger上的一��老文�?br>曄��很好奇线�E�池是怎么实现的，.net中有现成的线�E�池可以使用�Q�但是java中没有。还有就是Servlet的service�Ҏ��是怎么样�ؓ每一�?Request在不同的�U�程中独立服务的�Q�由于Servlet接口没有�l�承自Runnable接口�Q�因此无法直接由一个Servlet对象生成多个�U�程。后来在�|�上扑ֈ�了一个java版本的线�E�池的例子（http://www.informit.com/articles/article.asp?p= 30483&seqNum=1&rl=1�Q�在该例子的基础上简化得��C��下面�q�个版本的java�U�程池，记录在这里�?

*******************
ThreadPool.java
*******************

package threadPool;

import java.util.ArrayList;
import java.util.Collection;

public class ThreadPool
{
    Thread[] threadArray;
    Collection<Runnable> jobs = new ArrayList<Runnable>();

    public ThreadPool(int threadNum)
    {
        threadArray = new WorkerThread[threadNum];
        for (Thread thread : threadArray)
        {
            thread = new WorkerThread();
            thread.start();
        }
    }

    public synchronized void addJob(Runnable job)
    {
        jobs.add(job);
        notify();
    }

    private synchronized Runnable getJob()
    {
        while(jobs.isEmpty())
        {
            try
            {
                wait();
            } catch (InterruptedException e)
            {
                e.printStackTrace();
            }
        }
        Runnable job =  jobs.iterator().next();
        jobs.remove(job);
        return job;
    }

    private class WorkerThread extends Thread
    {
        public void run()
        {
            Runnable job = null;
            while(job == null)
            {
                job = getJob();
                if(job != null)
                {
                    job.run();
                }
                job = null;
            }
       }
    }
}

*******************
ThreadPoolTest.java
*******************

package threadPool;

public class ThreadTest
{
    private static class PrintClass implements Runnable
    {
        private int threadNo;

        public PrintClass(int threadNo)
        {
            this.threadNo = threadNo;
        }

        public void run()
        {
            for(int i = 0; i < 10; i++)
            {
                synchronized (System.out)
                {
                    System.out.println("Thread "+threadNo+": "+i);
                }
                try
                {
                    Thread.sleep(1000);
                } catch (InterruptedException e)
                {
                    e.printStackTrace();
                }
            }
        }
    }

    public static void main(String[] args)
    {
        ThreadPool tp = new ThreadPool(3);
        for(int i=0; i <10; i++)
        {
            tp.addJob(new PrintClass(i));
        }
        synchronized (System.out)
        {
            System.out.println("Job adding finished");
        }
    }
}

Job Hu 2007-05-15 12:53 发表评论

Job Hu — Wed, 25 Apr 2007 14:21:00 GMT

包org.apache.catalina主要由接口组成。我们可以把�q�些接口分�ؓ几个大类�?

�W�一�c�L��口主要是对web application及其各个�l�成部分的抽象。这些接口以Container为父接口�Q�分别�ؓContext�Q�Engine�Q�Host�Q�Wrapper�?

Engine代表的是整个Catalina Servlet引擎�?

Host代表的是Catalina Servlet引擎中的一个虚拟主机�?

Context

Wrapper代表的是某一个具体的servlet

下面我从Container的抽象实现ContainerBase来切入Container�Q�Context�Q�Engine�Q�Host�Q�Wrapper的实现�?

�׃��Container接口是web application中各部分的抽象的公共部分�Q�因此其实现�c�ContrainerBase是一个抽象类。对于Container接口的各个子接口的实现类�Q�则通过�l�承ContainerBase来实现接口Container接口。例如Engine接口�l�承Container接口�Q�Engine的实现类StandardEnginer�l�承ContainerBase�c�R�?

ContainerBase实现得接口有Container�Q�Lifecycle�Q�MBeanRegistration, Pipeline�Q�Serializable。其中Lifecycle�Q�Pipeline和Container属于同一个包�?

Lifecycle接口定义了一个具有生命期属性的�l��g所必须提供的方法：start�Q�启动一个组�Ӟ��Q�stop�Q�停止一个组�Ӟ��Q�除此之外该接口�q�定义了与具有生命期属性的�l��g的Listener相关�?个方法，用来��d��、删除、查扑֯�该组件的生命期阶�D�变化感兴趣的Listener�?

Pipeline在Tomcat中是一个或者多个Value的组合，Value用来对Request�q�行处理�Q�生成Response或者将Request和Response传给下一个Value�q�行处理。Tomcat�q�没有象通常一样将Pipeline和Value作�ؓ同一个接口，即��用Composite模式�Q�而是Pipeline和Value分别作�ؓ集合和元素，Pipeline只能加入Value而不能加入Pipeline�Q�Value则不能包含�Q何子Value�?

ContainerBase对lifecycle接口的实现分��Z��c�，addLifecycleListener、findLifecycleListener、removeLifecycleListener都是通过调用ContainerBase的一个LifecycleSupport成员实现�Q�start和stop�Ҏ��则�ؓContainerBase自己实现。我一开始以为LifecycleSupport也实��C��lifecycle接口�Q�但实际上�ƈ不是�q�样�Q�原因是start和stop�Ҏ��与具体的�l��g密切相关。此外LifecycleSupport中还包括一个名为fireLifecycleEvent的方法，该方法遍历所有的LifeCycleListener�Q��ƈ触发Lifecycle事�g。��M��上看LifecycleSupport实现了所有实现Lifecycle接口的组件的公共部分�Q�维护一个LifecycleListener的数�l�，提供了添加、修攏V��获取LifecycleListener和触发各个Listener的方法。一个有��的情况是，LifecycleSupport是一个final�c�，无法被��承，利用java的语�a�性质强制执行了面向对象中�l�合优于�l�承的思想�?/p>

Job Hu 2007-04-25 22:21 发表评论

丝袜美腿一区二区三区,亚洲欧洲精品一区二区,在线播放一区二区三区

实现一个栈,使其push,pop,min(取得栈中的最���元�?均�ؓO(1)

Byte in Java

Java Language Keywords

实现一个栈,使其push,pop,min(取得栈中的最��元�?均�ؓO(1)