Fractional Futurist

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Category: Java

  • Consuming Twitter streams from Java

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    A while ago I was playing with the Twitter Streaming API, one of the first things I wanted to do was collect a lot of data for off-line analysis (in Hadoop).  I wrote a hacky little utility class called TwitterConsumer.java that did just the trick. Basically you just initialise it with a valid Twitter account…

  • Reading ZIP files from Hadoop Map/Reduce

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    This post has been obsoleted by my update here: Hadoop: Processing ZIP files in Map/Reduce One of the first use-cases I had for playing with Apache Hadoop involved extracting and parsing the contents of thousands of ZIP files.  Hadoop doesn’t have a built-in reader for ZIP files, it just sees them as binary blobs. To solve…

  • Velocimacro – Generate a HTML Select box and its Options

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    A quick and simple Velocimacro to generate HTML Select boxes and its Options; automatically selects the correct option based on the value given. You can place this #macro anywhere in your Velocity templates but I used my global VM_global_library.vm file. Code [code] #macro( generateSelectBox $name $options $value ) #foreach ( $option in $options ) #set(…

  • Java Document to String

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    This is a very simple utility function to produce an indented XML document as a String given a Document. It throws a TransformerException if anything drastic goes wrong. [java] import java.io.*; import org.w3c.dom.Document; import javax.xml.transform.*; import javax.xml.transform.dom.DOMSource; … public static String documentToString( Document document ) throws TransformerException { TransformerFactory tFactory = TransformerFactory.newInstance(); Transformer transformer =…

  • Java Object Digester

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    I was working on a web-based application recently and wanted a lazy way to get data from a simple ‘value object’ out to the front end without having any hard-coded field names; I came up with this. Basically, this method will take any Object, iterate through its methods looking for any of the format “get<something>”…

  • Java Snippet – ANT Jar Task

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    Builds a JAR file Test.jar and generates a manifest specifying that class Test is the Main-Class. [xml] [/xml]

  • Java Snippet – Using SecureRandom

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    A better random number generator [java] import java.security.SecureRandom; … public static SecureRandom random = null; static { try { random = SecureRandom.getInstance(“SHA1PRNG”); random.setSeed( random.generateSeed(256) ); } catch( Exception e ) { e.printStackTrace(); } } [/java]

  • Java Snippet – Fast File Copy

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    When using JDK 1.4 and above… [java] public static void copyFile(File in, File out) { try { FileChannel sourceChannel = new FileInputStream(in).getChannel(); FileChannel destinationChannel = new FileOutputStream(out).getChannel(); sourceChannel.transferTo(0, sourceChannel.size(), destinationChannel); // or, you can also copy it this way // destinationChannel.transferFrom(sourceChannel, 0, sourceChannel.size()); sourceChannel.close(); destinationChannel.close(); } catch ( Exception e ) { e.printStackTrace(); } }…

  • Java Snippet – Recursive Directory Deletion

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    Returns true on success, false on failure: [java] public static boolean deleteDir(File dir) { if (dir.isDirectory()) { String[] children = dir.list(); for (int i=0; i<children.length; i++) { boolean success = deleteDir(new File(dir, children[i])); if (!success) { return false; } } } return dir.delete(); } [/java]