11 2012 档案

摘要：1.单线程实现package com.mime; import java.io.File; public class TotalFileSizeSequential { private long getTotalSizeOfFilesInDir(final File file) { if (file.isFile()) return file.length(); final File[] children = file.listFiles(); long total = 0; if (children != null) for (final File chil... 阅读全文

摘要：我们先看下面一个示例 public class RaceCondition { private static boolean done; public static void main(final String[] args) throws InterruptedException { new Thread(new Runnable() { public void run() { int i = 0; while (!done) { i++; } System.out.println("Done!"); } }).start... 阅读全文

摘要：public abstract class AbstractPrimeFinder { public boolean isPrime(final int number) { if (number <= 1) return false; for (int i = 2; i <= Math.sqrt(number); i++) if (number % i == 0) return false; return true; } public int countPrimesInRange(final int lower, final int upper) { ... 阅读全文

摘要：字典树查找，Trie,又称字典树、单词查找树,是一种树形结构，用于保存大量的字符串。它的优点是：利用字符串的公共前缀来节约存储空间。package com.jwetherell.algorithms.data_structures; import java.util.Arrays; /** * A trie, or prefix tree, is an ordered tree data structure that is used to * store an associative array where the keys are usually strings. * * =... 阅读全文

摘要：区间树可以统计某个区间对应的重复的区间package com.jwetherell.algorithms.data_structures; import java.security.InvalidParameterException; import java.util.ArrayList; import java.util.Comparator; import java.util.Iterator; import java.util.List; import java.util.Set; import java.util.TreeSet; /** * An interval tree ... 阅读全文

摘要：1.到这里下载apache的最新版2.4.3http://httpd.apache.org/download.cgi#apache242.先安装apache需要的几个模块下载所需软件包： wget http://archive.apache.org/dist/apr/apr-1.4.5.tar.gz wget http://archive.apache.org/dist/apr/apr-util-1.3.12.tar.gz wget http://jaist.dl.sourceforge.net/project/pcre/pcre/8.10/pcre-8.10.zip 具体步骤如下... 阅读全文

摘要：最近重新学习数据结构和算法，刚刚看完java版的这几个数据结构，比较浅显易懂，有兴趣的可以自己去调试学习，关于这几个的介绍网上很多。二叉搜索树，比较简单的树结构了package com.jwetherell.algorithms.data_structures; import java.util.ArrayDeque; import java.util.ArrayList; import java.util.List; import java.util.Random; import java.util.Queue; /** * A binary search tree (BST), wh... 阅读全文

摘要：1.到mysql网站下载mysql cluster版本http://www.mysql.com/downloads/cluster/ 下载到/home/weijianzhongwj/software下2.安装mysql clustercd /home/weijianzhongwj/software tar xvfmysql-cluster-gpl-7.2.8-linux2.6-i686.tar.gz ln -smysql-cluster-gpl-7.2.8-linux2.6-i686 mysqlc在$HOME/.bashrc增加 export PATH=$PATH:/home/weijianz 阅读全文

摘要：我使用的ubutun，安装用apt-get非常方便。weijianzhongwj@ubuntu:~$ dstat You did not select any stats, using -cdngy by default. ----total-cpu-usage---- -dsk/total- -net/total- ---paging-- ---system-- usr sys idl wai hiq siq| read writ| recv send| in out | int csw 16 5 77 2 0 1| 181k 147k| 0 ... 阅读全文

摘要：public OfferInfo parseXml(String content) throws NumberFormatException, XMLStreamException { if (content == null || content.isEmpty()) { return null; } XMLInputFactory factory = XMLInputFactory.newInstance(); XMLStreamReader reader = null; try ... 阅读全文

摘要：1.先去hadoop官网下载hadoop的源码http://svn.apache.org/repos/asf/hadoop/common/trunk2.下载maven3，当前hadoop的最新版必须使用maven3编译3.到hadoop下载源码目录执行mvn clean install；mvn eclipse:eclipse；4.将源码导入eclipse；5.在eclipse设置执行的WordCount.java的jvm启动参数，最少需要两个，输入目录和输出目录6.然后就可以设置断点进行调试了，我们在处理mapreduce的主干流程上设置断点org.apache.hadoop.mapred.L 阅读全文

摘要：在Arrays.java中的sort中 public static void sort(Object[] a, int fromIndex, int toIndex) { if (LegacyMergeSort.userRequested) legacyMergeSort(a, fromIndex, toIndex); else ComparableTimSort.sort(a, fromIndex, toIndex); } /** To be removed in a future rel... 阅读全文

摘要：/* * Copyright (c) 1996, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * publishe... 阅读全文

摘要：在java中可能很多人都会忽略数据结构（类似树，跳跃表等），大家都比较熟悉链表，数组，栈，队列，哈希表等。最近看了jdk中关于树和跳跃表等的实现，其实数据结构真的是基础，有兴趣的java程序员可以翻开jdk的代码仔细阅读下面几种数据结构的学习。TreeMap:红黑树http://v.163.com/movie/2010/12/9/J/M6UTT5U0I_M6V2TJ49J.html这里有网易公开课的教学视频PriorityQueue：最小堆比较简单的一种实现，queue[n]的左右儿子是queue[2*n+1]和queue[2*n+2]，每次根据排序类取第一个queue[0],然后把queue 阅读全文