I’m currently working on moving a Tomcat-based application into EC2. The code was written for Java 5.0. While Java 6 would probably work, I’d like to keep everything as “same” as possible, since EC2 presents its own challenges. I spun up a couple of t1.micro instances and copied everything over, including the Java 5 JDK, jdk-1_5_0_22-linux-amd64.rpm. Installing from RPM was easy, but the EC2 instance defaults to using OpenJDK 1.6:

[root@ec2 ~]# java -version
java version "1.6.0_20"
OpenJDK Runtime Environment (IcedTea6 1.9.10) (amazon-52.1.9.10.40.amzn1-x86_64)
OpenJDK 64-Bit Server VM (build 19.0-b09, mixed mode)

There were a couple of things I had to do to get the system to accept the Sun JDK as its “real” java.

Alternatives

Red Hat’s “alternatives” system is designed to allow a system to have multiple versions of a program installed and make it easy to choose which one you want to run. Unfortunately I’ve found the syntax a bit strange and always have to Google it, so I figured I’d document it here for posterity.

So here’s the default:

[root@ec2 ~]# alternatives --config java
 
There is 1 program that provides 'java'.
 
  Selection    Command
-----------------------------------------------
*+ 1           /usr/lib/jvm/jre-1.6.0-openjdk.x86_64/bin/java
 
Enter to keep the current selection[+], or type selection number:

Here’s how to add Sun java, assuming the java binary is in /usr/java/jdk1.5.0_22/jre/bin/java (where the RPM puts it).

[root@ec2 ~]# alternatives --install /usr/bin/java java /usr/java/jdk1.5.0_22/jre/bin/java 1
[root@ec2 ~]# alternatives --config java
There are 2 programs which provide 'java'.
 
  Selection    Command
-----------------------------------------------
*+ 1           /usr/lib/jvm/jre-1.6.0-openjdk.x86_64/bin/java
   2           /usr/java/jdk1.5.0_22/jre/bin/java
 
Enter to keep the current selection[+], or type selection number: 2
[root@ec2 ~]# java -version
java version "1.5.0_22"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_22-b03)
Java HotSpot(TM) 64-Bit Server VM (build 1.5.0_22-b03, mixed mode)

Yay! Unfortunately this doesn’t help with the other problem I had with Tomcat, which was that EC2 instances set the JAVA_HOME var to OpenJDK as well (/usr/lib/jvm/jre). Fortunately this is an easy fix as well.

Setting JAVA_HOME

The JAVA_HOME var is set in /etc/profile.d/aws-apitools-common.sh. Comment out this line:

export JAVA_HOME=/usr/lib/jvm/jre

Create a new file, /etc/profile.d/sun-java.sh, and put this in it:

export JAVA_HOME=/usr/java/jdk1.5.0_22/jre

Also in that file I added the following to instruct the JVM to process all dates in America/New_York, since that’s the timezone all of our other servers use, and it makes reading log files easier when all dates are in the same tz:

export TZ=America/New_York

(I found I had to do this even after pointing /etc/localtime to the correct zoneinfo – Java was stuck on UTC even after the rest of the system was using America/New_York.)

I’m currently in the process of moving our DNS over to another provider and I was curious as to whether the old or new provider offers faster lookups. dig shows query times, but I didn’t want to just run that over and over. I decided to write something to do this, in Java since I like Java. I found this post, which has the meat of the work done already. I also read some of Sun’s JNDI/DNS lookup info, which was pretty dense. All I want to do is specify the name server’s IP and do the lookup. I don’t even really care about the result, just how long the query takes.

The thing I wrote only looks up A records, but can easily be modified to do CNAMEs or whatever. Here’s how you call it:

$ java -jar DNSTester.jar 4.2.2.2 www.google.com 25
Resolved www.google.com to 74.125.235.19 against NS 4.2.2.2
Performed 25 lookups in 233.29 milliseconds.  Average 9.3316ms per lookup.
 
$ java -jar DNSTester.jar 8.8.4.4 www.google.com 25
Resolved www.google.com to 74.125.226.146 against NS 8.8.4.4
Performed 25 lookups in 450.034 milliseconds.  Average 18.00136ms per lookup.

Code is in github here. Jar is available here.

Java has functionality for calculating SHA-1 and MD5 checksums but not for displaying them as the 40-char hex strings I’m used to. I want to update my photo reorganizer so it doesn’t create duplicate files so I figured this would be a handy thing to write. I wrote one for MD5 a while ago (the only code you really need to write is the byte-array-to-hex-string converter) but I guess I lost it. Anyway, here it is.

Edit: Rather than paste a huge useless block of code here, I put it on github: https://github.com/evandhoffman/Java-SHA-1-Hasher.

Output appears to match that of the command-line utility:

[evan@EvanMBP bin]$ java -jar SHA1.jar ~/text.txt 
3bbed58697cc1775e8fadcf1324e26d4d092e7c2        /Users/evan/text.txt
[evan@EvanMBP bin]$ shasum ~/text.txt 
3bbed58697cc1775e8fadcf1324e26d4d092e7c2  /Users/evan/text.txt

It’s not as fast as shasum (as I expected) but that may partially be due to reading data in 1k chunks.

Someone recently asked me how to do this, so I figured I’d write it up in Java since it’s still the language I’m most comfortable with:

Node.java

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package com.evanhoffman.bst;
 
import org.apache.log4j.Logger;
 
/**
 * Node in a binary search tree in which values < are in the left branch and 
 * values >= are in the right branch.
 * @author evan
 *
 * @param <V>
 */
public class Node<V extends Comparable<V>> {
	private static Logger logger = Logger.getLogger(Node.class);
 
	private Node<V> left = null;
	private Node<V> right = null;
	private V value = null;
 
	public Node(V t) {
		this.value = t;
	}
 
	public V getValue() {
		return value;
	}
	public boolean isLeaf() {
		return (left == null && right == null);
	}
 
 
	public void addNode(Node<V> node) {
		if (node.getValue().compareTo(value) < 0) {
			if (left == null) {
				left = node;
				logger.debug("Assigning "+node.getValue()+" "+
						"to left child of node "+value);
			} else {
				left.addNode(node);
			}
		} else {
			if (right == null) {
				right = node;
				logger.debug("Assigning "+node.getValue()+" "+
						"to right child of node "+value);
			} else {
				right.addNode(node);
			}
		}
 
	}
 
	public V findMaxStrictlyLessThan(V t) {
		return findMaxStrictlyLessThan(t, null);
	}
 
	/**
	 * Returns the greatest value in the tree strictly
	 * less than (as defined by {@link Comparable#compareTo(Object)} the given value.
	 * @param t
	 * @return
	 */
	private V findMaxStrictlyLessThan(V t, V currentMax) {
		if (t.compareTo(value) < 0) {
			logger.debug(t +" is less than current node "+value+", checking left (if it exists)");
			return left == null ? currentMax : left.findMaxStrictlyLessThan(t, currentMax);
		} else {
			logger.debug(t +" is >= current node "+value+", checking right (if exists)");
			currentMax = value;
			return right == null ? currentMax : right.findMaxStrictlyLessThan(t, currentMax);
		}
 
	}
 
	@Override
	public String toString() {
		if (isLeaf()) {
			return "{value="+value+"}";
		} else {
			return "{value="+value+", left="+left+", right="+right+"}";
		}
	}
 
}

IntBstBuilder.java:

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package com.evanhoffman.bst;
 
import java.util.Random;
 
import org.apache.log4j.BasicConfigurator;
import org.apache.log4j.Logger;
 
public class IntBstBuilder {
 
	private static int min = 0;
	private static int max = 200;
	private static int size = 10;
 
	private static Random rng = new Random();
	private static Logger logger = Logger.getLogger(IntBstBuilder.class);
 
	public static void main(String args[]) {
		BasicConfigurator.configure();
 
		Node<Integer> root = new Node<Integer>((max - min)/2);
		for (int i = 0; i < size; i++) {
			int num = (Math.abs(rng.nextInt()) % (max - min)) + min;
			Node<Integer> newNode = new Node<Integer>(num);
			root.addNode(newNode);
		}
 
		logger.info(root);
 
		logger.info(root.findMaxStrictlyLessThan(50));
		logger.info(root.findMaxStrictlyLessThan(90));
		logger.info(root.findMaxStrictlyLessThan(130));
		logger.info(root.findMaxStrictlyLessThan(220));
		logger.info(root.findMaxStrictlyLessThan(-100));
 
	}
}

Output:

0 [main] DEBUG com.evanhoffman.bst.Node  - Assigning 192 to right child of node 100
1 [main] DEBUG com.evanhoffman.bst.Node  - Assigning 140 to left child of node 192
1 [main] DEBUG com.evanhoffman.bst.Node  - Assigning 162 to right child of node 140
1 [main] DEBUG com.evanhoffman.bst.Node  - Assigning 54 to left child of node 100
1 [main] DEBUG com.evanhoffman.bst.Node  - Assigning 155 to left child of node 162
1 [main] DEBUG com.evanhoffman.bst.Node  - Assigning 118 to left child of node 140
2 [main] DEBUG com.evanhoffman.bst.Node  - Assigning 52 to left child of node 54
2 [main] DEBUG com.evanhoffman.bst.Node  - Assigning 184 to right child of node 162
2 [main] DEBUG com.evanhoffman.bst.Node  - Assigning 41 to left child of node 52
2 [main] DEBUG com.evanhoffman.bst.Node  - Assigning 161 to right child of node 155
2 [main] INFO com.evanhoffman.bst.IntBstBuilder  - {value=100, left={value=54, left={value=52, left={value=41}, right=null}, right=null}, right={value=192, left={value=140, left={value=118}, right={value=162, left={value=155, left=null, right={value=161}}, right={value=184}}}, right=null}}
2 [main] DEBUG com.evanhoffman.bst.Node  - 50 is less than current node 100, checking left (if it exists)
2 [main] DEBUG com.evanhoffman.bst.Node  - 50 is less than current node 54, checking left (if it exists)
2 [main] DEBUG com.evanhoffman.bst.Node  - 50 is less than current node 52, checking left (if it exists)
2 [main] DEBUG com.evanhoffman.bst.Node  - 50 is >= current node 41, checking right (if exists)
2 [main] INFO com.evanhoffman.bst.IntBstBuilder  - 41
2 [main] DEBUG com.evanhoffman.bst.Node  - 90 is less than current node 100, checking left (if it exists)
2 [main] DEBUG com.evanhoffman.bst.Node  - 90 is >= current node 54, checking right (if exists)
2 [main] INFO com.evanhoffman.bst.IntBstBuilder  - 54
2 [main] DEBUG com.evanhoffman.bst.Node  - 130 is >= current node 100, checking right (if exists)
2 [main] DEBUG com.evanhoffman.bst.Node  - 130 is less than current node 192, checking left (if it exists)
3 [main] DEBUG com.evanhoffman.bst.Node  - 130 is less than current node 140, checking left (if it exists)
3 [main] DEBUG com.evanhoffman.bst.Node  - 130 is >= current node 118, checking right (if exists)
3 [main] INFO com.evanhoffman.bst.IntBstBuilder  - 118
3 [main] DEBUG com.evanhoffman.bst.Node  - 220 is >= current node 100, checking right (if exists)
3 [main] DEBUG com.evanhoffman.bst.Node  - 220 is >= current node 192, checking right (if exists)
3 [main] INFO com.evanhoffman.bst.IntBstBuilder  - 192
3 [main] DEBUG com.evanhoffman.bst.Node  - -100 is less than current node 100, checking left (if it exists)
3 [main] DEBUG com.evanhoffman.bst.Node  - -100 is less than current node 54, checking left (if it exists)
3 [main] DEBUG com.evanhoffman.bst.Node  - -100 is less than current node 52, checking left (if it exists)
3 [main] DEBUG com.evanhoffman.bst.Node  - -100 is less than current node 41, checking left (if it exists)
3 [main] INFO com.evanhoffman.bst.IntBstBuilder  - 

StringBstBuilder.java:

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package com.evanhoffman.bst;
 
import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Random;
 
import org.apache.log4j.BasicConfigurator;
import org.apache.log4j.Logger;
 
public class StringBstBuilder {
 
	private static int size = 100;
 
	private static Random rng = new Random();
	private static Logger logger = Logger.getLogger(StringBstBuilder.class);
 
	private ArrayList<String> words = new ArrayList<String>();
 
	public ArrayList<String> getWords() {
		return words;
	}
 
 
 
	StringBstBuilder(File f, int maxLines) {
 
		logger.debug("Creating "+this.getClass()+" with word list file: "+f+" up to "+maxLines+" lines");
 
		int i = 0;
		try {
			BufferedReader br = new BufferedReader(new FileReader(f));
			String line = null;
			while ((i < maxLines) && (line = br.readLine()) != null) {
				words.add(line);
				i++;
			}
			logger.debug("Added "+words.size()+" words to list");
 
		} catch (FileNotFoundException fe) {
			logger.error("File not found: "+f,fe);
			throw new RuntimeException(fe);
		} catch (IOException ie) {
			logger.error("IO Exception: "+ie.getMessage(),ie);
			throw new RuntimeException(ie);
		}
	}
 
 
 
	public static void main(String args[]) {
		BasicConfigurator.configure();
 
		StringBstBuilder sbt = new StringBstBuilder(new File(args[0]), Integer.parseInt(args[1]));
 
		ArrayList<String> words = sbt.getWords();
 
		int wordListSize = words.size();
 
		// Random number between 1/4 and 3/4 through the list.
		int seedWordIndex = (Math.abs(rng.nextInt()) % (wordListSize/2)) + (wordListSize / 4);
 
		Node<String> root = new Node<String>(words.get(seedWordIndex));
		logger.debug("Root word: "+root.getValue());
 
		for (int i = 0; i < size; i++) {
			int index = (Math.abs(rng.nextInt()) % (words.size()));
			Node<String> newNode = new Node<String>(words.get(index));
			root.addNode(newNode);
		}
 
		logger.info("Entire tree: "+root);
 
		String[] searches = {"andy", "joker", "kale", "moonshine", "zebra"};
		for (String str : searches) {
			logger.info("Search for "+str+": ");
			String s = root.findMaxStrictlyLessThan(str);
			logger.info("max word: "+s);
		}
 
	}
}

Output:

0 [main] DEBUG com.evanhoffman.bst.StringBstBuilder  - Creating class com.evanhoffman.bst.StringBstBuilder with word list file: /Users/evan/Downloads/scowl-7.1/final/english-words.20 up to 10000 lines
47 [main] DEBUG com.evanhoffman.bst.StringBstBuilder  - Added 7951 words to list
48 [main] DEBUG com.evanhoffman.bst.StringBstBuilder  - Root word: patient's
48 [main] DEBUG com.evanhoffman.bst.Node  - Assigning scroll's to right child of node patient's
48 [main] DEBUG com.evanhoffman.bst.Node  - Assigning dual to left child of node patient's
48 [main] DEBUG com.evanhoffman.bst.Node  - Assigning bat to left child of node dual
48 [main] DEBUG com.evanhoffman.bst.Node  - Assigning moderate to right child of node dual
48 [main] DEBUG com.evanhoffman.bst.Node  - Assigning abort to left child of node bat
48 [main] DEBUG com.evanhoffman.bst.Node  - Assigning migrates to left child of node moderate
48 [main] DEBUG com.evanhoffman.bst.Node  - Assigning terrifying to right child of node scroll's
48 [main] DEBUG com.evanhoffman.bst.Node  - Assigning equilibrium to left child of node migrates
48 [main] DEBUG com.evanhoffman.bst.Node  - Assigning polynomial to left child of node scroll's
48 [main] DEBUG com.evanhoffman.bst.Node  - Assigning tomatoes to right child of node terrifying
48 [main] DEBUG com.evanhoffman.bst.Node  - Assigning unusable to right child of node tomatoes
48 [main] DEBUG com.evanhoffman.bst.Node  - Assigning nailing to right child of node moderate
48 [main] DEBUG com.evanhoffman.bst.Node  - Assigning supporter to left child of node terrifying
49 [main] DEBUG com.evanhoffman.bst.Node  - Assigning prosecution to right child of node polynomial
49 [main] DEBUG com.evanhoffman.bst.Node  - Assigning management to right child of node equilibrium
49 [main] DEBUG com.evanhoffman.bst.Node  - Assigning disabled to right child of node bat
49 [main] DEBUG com.evanhoffman.bst.Node  - Assigning planted to left child of node polynomial
49 [main] DEBUG com.evanhoffman.bst.Node  - Assigning midday to right child of node management
49 [main] DEBUG com.evanhoffman.bst.Node  - Assigning cloth to left child of node disabled
49 [main] DEBUG com.evanhoffman.bst.Node  - Assigning hip to left child of node management
49 [main] DEBUG com.evanhoffman.bst.Node  - Assigning tune's to left child of node unusable
49 [main] DEBUG com.evanhoffman.bst.Node  - Assigning mortal to left child of node nailing
49 [main] DEBUG com.evanhoffman.bst.Node  - Assigning dangers to right child of node cloth
49 [main] DEBUG com.evanhoffman.bst.Node  - Assigning concentrate to left child of node dangers
49 [main] DEBUG com.evanhoffman.bst.Node  - Assigning intimate to right child of node hip
49 [main] DEBUG com.evanhoffman.bst.Node  - Assigning stairs to left child of node supporter
49 [main] DEBUG com.evanhoffman.bst.Node  - Assigning attorney to right child of node abort
49 [main] DEBUG com.evanhoffman.bst.Node  - Assigning globally to left child of node hip
49 [main] DEBUG com.evanhoffman.bst.Node  - Assigning vertical to right child of node unusable
49 [main] DEBUG com.evanhoffman.bst.Node  - Assigning close's to left child of node cloth
49 [main] DEBUG com.evanhoffman.bst.Node  - Assigning debatable to right child of node dangers
50 [main] DEBUG com.evanhoffman.bst.Node  - Assigning guarding to right child of node globally
50 [main] DEBUG com.evanhoffman.bst.Node  - Assigning aided to left child of node attorney
50 [main] DEBUG com.evanhoffman.bst.Node  - Assigning contend to right child of node concentrate
50 [main] DEBUG com.evanhoffman.bst.Node  - Assigning shined to left child of node stairs
50 [main] DEBUG com.evanhoffman.bst.Node  - Assigning journals to right child of node intimate
50 [main] DEBUG com.evanhoffman.bst.Node  - Assigning warmed to right child of node vertical
50 [main] DEBUG com.evanhoffman.bst.Node  - Assigning blaming to left child of node close's
50 [main] DEBUG com.evanhoffman.bst.Node  - Assigning ingredient to left child of node intimate
50 [main] DEBUG com.evanhoffman.bst.Node  - Assigning gleaning to left child of node globally
50 [main] DEBUG com.evanhoffman.bst.Node  - Assigning boys to right child of node blaming
50 [main] DEBUG com.evanhoffman.bst.Node  - Assigning stream's to right child of node stairs
50 [main] DEBUG com.evanhoffman.bst.Node  - Assigning tragedy to left child of node tune's
50 [main] DEBUG com.evanhoffman.bst.Node  - Assigning brands to right child of node boys
50 [main] DEBUG com.evanhoffman.bst.Node  - Assigning revenge to right child of node prosecution
50 [main] DEBUG com.evanhoffman.bst.Node  - Assigning knight to right child of node journals
50 [main] DEBUG com.evanhoffman.bst.Node  - Assigning discard to right child of node disabled
50 [main] DEBUG com.evanhoffman.bst.Node  - Assigning successor to right child of node stream's
51 [main] DEBUG com.evanhoffman.bst.Node  - Assigning synonymous to right child of node supporter
51 [main] DEBUG com.evanhoffman.bst.Node  - Assigning bow to left child of node boys
51 [main] DEBUG com.evanhoffman.bst.Node  - Assigning satisfaction to right child of node revenge
51 [main] DEBUG com.evanhoffman.bst.Node  - Assigning mutters to right child of node mortal
51 [main] DEBUG com.evanhoffman.bst.Node  - Assigning tray to right child of node tragedy
51 [main] DEBUG com.evanhoffman.bst.Node  - Assigning linkage to right child of node knight
51 [main] DEBUG com.evanhoffman.bst.Node  - Assigning face's to left child of node gleaning
51 [main] DEBUG com.evanhoffman.bst.Node  - Assigning decreasing to right child of node debatable
51 [main] DEBUG com.evanhoffman.bst.Node  - Assigning spoiling to right child of node shined
51 [main] DEBUG com.evanhoffman.bst.Node  - Assigning slave's to left child of node spoiling
51 [main] DEBUG com.evanhoffman.bst.Node  - Assigning clarified to right child of node brands
51 [main] DEBUG com.evanhoffman.bst.Node  - Assigning inspection to right child of node ingredient
51 [main] DEBUG com.evanhoffman.bst.Node  - Assigning technically to right child of node synonymous
51 [main] DEBUG com.evanhoffman.bst.Node  - Assigning supervises to right child of node successor
51 [main] DEBUG com.evanhoffman.bst.Node  - Assigning disconnect to right child of node discard
51 [main] DEBUG com.evanhoffman.bst.Node  - Assigning whence to right child of node warmed
51 [main] DEBUG com.evanhoffman.bst.Node  - Assigning creator to right child of node contend
52 [main] DEBUG com.evanhoffman.bst.Node  - Assigning oppress to right child of node nailing
52 [main] DEBUG com.evanhoffman.bst.Node  - Assigning magnificent to right child of node linkage
52 [main] DEBUG com.evanhoffman.bst.Node  - Assigning launch to left child of node linkage
52 [main] DEBUG com.evanhoffman.bst.Node  - Assigning compensation to left child of node concentrate
52 [main] DEBUG com.evanhoffman.bst.Node  - Assigning cave to left child of node clarified
52 [main] DEBUG com.evanhoffman.bst.Node  - Assigning unbearable to right child of node tune's
52 [main] DEBUG com.evanhoffman.bst.Node  - Assigning verifies to left child of node vertical
52 [main] DEBUG com.evanhoffman.bst.Node  - Assigning compact to left child of node compensation
52 [main] DEBUG com.evanhoffman.bst.Node  - Assigning immense to left child of node ingredient
52 [main] DEBUG com.evanhoffman.bst.Node  - Assigning empire to left child of node equilibrium
52 [main] DEBUG com.evanhoffman.bst.Node  - Assigning foreseeable to right child of node face's
52 [main] DEBUG com.evanhoffman.bst.Node  - Assigning joking to left child of node journals
52 [main] DEBUG com.evanhoffman.bst.Node  - Assigning opts to right child of node oppress
52 [main] DEBUG com.evanhoffman.bst.Node  - Assigning convicting to left child of node creator
52 [main] DEBUG com.evanhoffman.bst.Node  - Assigning divisions to right child of node disconnect
52 [main] DEBUG com.evanhoffman.bst.Node  - Assigning fascinate to left child of node foreseeable
52 [main] DEBUG com.evanhoffman.bst.Node  - Assigning reactions to left child of node revenge
52 [main] DEBUG com.evanhoffman.bst.Node  - Assigning discriminated to left child of node divisions
53 [main] DEBUG com.evanhoffman.bst.Node  - Assigning unrealistic to right child of node unbearable
53 [main] DEBUG com.evanhoffman.bst.Node  - Assigning crowds to right child of node creator
53 [main] DEBUG com.evanhoffman.bst.Node  - Assigning marketed to left child of node midday
53 [main] DEBUG com.evanhoffman.bst.Node  - Assigning broad to left child of node cave
53 [main] DEBUG com.evanhoffman.bst.Node  - Assigning socket to right child of node slave's
53 [main] DEBUG com.evanhoffman.bst.Node  - Assigning verbal to left child of node verifies
53 [main] DEBUG com.evanhoffman.bst.Node  - Assigning register's to right child of node reactions
53 [main] DEBUG com.evanhoffman.bst.Node  - Assigning attributes to right child of node attorney
53 [main] DEBUG com.evanhoffman.bst.Node  - Assigning clarity to right child of node clarified
53 [main] DEBUG com.evanhoffman.bst.Node  - Assigning engage to right child of node empire
53 [main] DEBUG com.evanhoffman.bst.Node  - Assigning succeeded to left child of node successor
53 [main] DEBUG com.evanhoffman.bst.Node  - Assigning resembled to right child of node register's
53 [main] DEBUG com.evanhoffman.bst.Node  - Assigning kernel to left child of node knight
53 [main] DEBUG com.evanhoffman.bst.Node  - Assigning dot to right child of node divisions
53 [main] DEBUG com.evanhoffman.bst.Node  - Assigning wrecked to right child of node whence
54 [main] DEBUG com.evanhoffman.bst.Node  - Assigning gratuitously to left child of node guarding
54 [main] DEBUG com.evanhoffman.bst.Node  - Assigning syndicate to left child of node synonymous
54 [main] INFO com.evanhoffman.bst.StringBstBuilder  - Entire tree: {value=patient's, left={value=dual, left={value=bat, left={value=abort, left=null, right={value=attorney, left={value=aided}, right={value=attributes}}}, right={value=disabled, left={value=cloth, left={value=close's, left={value=blaming, left=null, right={value=boys, left={value=bow}, right={value=brands, left=null, right={value=clarified, left={value=cave, left={value=broad}, right=null}, right={value=clarity}}}}}, right=null}, right={value=dangers, left={value=concentrate, left={value=compensation, left={value=compact}, right=null}, right={value=contend, left=null, right={value=creator, left={value=convicting}, right={value=crowds}}}}, right={value=debatable, left=null, right={value=decreasing}}}}, right={value=discard, left=null, right={value=disconnect, left=null, right={value=divisions, left={value=discriminated}, right={value=dot}}}}}}, right={value=moderate, left={value=migrates, left={value=equilibrium, left={value=empire, left=null, right={value=engage}}, right={value=management, left={value=hip, left={value=globally, left={value=gleaning, left={value=face's, left=null, right={value=foreseeable, left={value=fascinate}, right=null}}, right=null}, right={value=guarding, left={value=gratuitously}, right=null}}, right={value=intimate, left={value=ingredient, left={value=immense}, right={value=inspection}}, right={value=journals, left={value=joking}, right={value=knight, left={value=kernel}, right={value=linkage, left={value=launch}, right={value=magnificent}}}}}}, right={value=midday, left={value=marketed}, right=null}}}, right=null}, right={value=nailing, left={value=mortal, left=null, right={value=mutters}}, right={value=oppress, left=null, right={value=opts}}}}}, right={value=scroll's, left={value=polynomial, left={value=planted}, right={value=prosecution, left=null, right={value=revenge, left={value=reactions, left=null, right={value=register's, left=null, right={value=resembled}}}, right={value=satisfaction}}}}, right={value=terrifying, left={value=supporter, left={value=stairs, left={value=shined, left=null, right={value=spoiling, left={value=slave's, left=null, right={value=socket}}, right=null}}, right={value=stream's, left=null, right={value=successor, left={value=succeeded}, right={value=supervises}}}}, right={value=synonymous, left={value=syndicate}, right={value=technically}}}, right={value=tomatoes, left=null, right={value=unusable, left={value=tune's, left={value=tragedy, left=null, right={value=tray}}, right={value=unbearable, left=null, right={value=unrealistic}}}, right={value=vertical, left={value=verifies, left={value=verbal}, right=null}, right={value=warmed, left=null, right={value=whence, left=null, right={value=wrecked}}}}}}}}}
55 [main] INFO com.evanhoffman.bst.StringBstBuilder  - Search for andy:
55 [main] DEBUG com.evanhoffman.bst.Node  - andy is less than current node patient's, checking left (if it exists)
55 [main] DEBUG com.evanhoffman.bst.Node  - andy is less than current node dual, checking left (if it exists)
55 [main] DEBUG com.evanhoffman.bst.Node  - andy is less than current node bat, checking left (if it exists)
55 [main] DEBUG com.evanhoffman.bst.Node  - andy is >= current node abort, checking right (if exists)
55 [main] DEBUG com.evanhoffman.bst.Node  - andy is less than current node attorney, checking left (if it exists)
55 [main] DEBUG com.evanhoffman.bst.Node  - andy is >= current node aided, checking right (if exists)
55 [main] INFO com.evanhoffman.bst.StringBstBuilder  - max word: aided
56 [main] INFO com.evanhoffman.bst.StringBstBuilder  - Search for joker:
56 [main] DEBUG com.evanhoffman.bst.Node  - joker is less than current node patient's, checking left (if it exists)
56 [main] DEBUG com.evanhoffman.bst.Node  - joker is >= current node dual, checking right (if exists)
56 [main] DEBUG com.evanhoffman.bst.Node  - joker is less than current node moderate, checking left (if it exists)
56 [main] DEBUG com.evanhoffman.bst.Node  - joker is less than current node migrates, checking left (if it exists)
56 [main] DEBUG com.evanhoffman.bst.Node  - joker is >= current node equilibrium, checking right (if exists)
56 [main] DEBUG com.evanhoffman.bst.Node  - joker is less than current node management, checking left (if it exists)
56 [main] DEBUG com.evanhoffman.bst.Node  - joker is >= current node hip, checking right (if exists)
56 [main] DEBUG com.evanhoffman.bst.Node  - joker is >= current node intimate, checking right (if exists)
56 [main] DEBUG com.evanhoffman.bst.Node  - joker is less than current node journals, checking left (if it exists)
56 [main] DEBUG com.evanhoffman.bst.Node  - joker is less than current node joking, checking left (if it exists)
56 [main] INFO com.evanhoffman.bst.StringBstBuilder  - max word: intimate
56 [main] INFO com.evanhoffman.bst.StringBstBuilder  - Search for kale:
56 [main] DEBUG com.evanhoffman.bst.Node  - kale is less than current node patient's, checking left (if it exists)
56 [main] DEBUG com.evanhoffman.bst.Node  - kale is >= current node dual, checking right (if exists)
56 [main] DEBUG com.evanhoffman.bst.Node  - kale is less than current node moderate, checking left (if it exists)
56 [main] DEBUG com.evanhoffman.bst.Node  - kale is less than current node migrates, checking left (if it exists)
56 [main] DEBUG com.evanhoffman.bst.Node  - kale is >= current node equilibrium, checking right (if exists)
57 [main] DEBUG com.evanhoffman.bst.Node  - kale is less than current node management, checking left (if it exists)
57 [main] DEBUG com.evanhoffman.bst.Node  - kale is >= current node hip, checking right (if exists)
57 [main] DEBUG com.evanhoffman.bst.Node  - kale is >= current node intimate, checking right (if exists)
57 [main] DEBUG com.evanhoffman.bst.Node  - kale is >= current node journals, checking right (if exists)
57 [main] DEBUG com.evanhoffman.bst.Node  - kale is less than current node knight, checking left (if it exists)
57 [main] DEBUG com.evanhoffman.bst.Node  - kale is less than current node kernel, checking left (if it exists)
57 [main] INFO com.evanhoffman.bst.StringBstBuilder  - max word: journals
57 [main] INFO com.evanhoffman.bst.StringBstBuilder  - Search for moonshine:
57 [main] DEBUG com.evanhoffman.bst.Node  - moonshine is less than current node patient's, checking left (if it exists)
57 [main] DEBUG com.evanhoffman.bst.Node  - moonshine is >= current node dual, checking right (if exists)
57 [main] DEBUG com.evanhoffman.bst.Node  - moonshine is >= current node moderate, checking right (if exists)
57 [main] DEBUG com.evanhoffman.bst.Node  - moonshine is less than current node nailing, checking left (if it exists)
57 [main] DEBUG com.evanhoffman.bst.Node  - moonshine is less than current node mortal, checking left (if it exists)
57 [main] INFO com.evanhoffman.bst.StringBstBuilder  - max word: moderate
57 [main] INFO com.evanhoffman.bst.StringBstBuilder  - Search for zebra:
57 [main] DEBUG com.evanhoffman.bst.Node  - zebra is >= current node patient's, checking right (if exists)
57 [main] DEBUG com.evanhoffman.bst.Node  - zebra is >= current node scroll's, checking right (if exists)
57 [main] DEBUG com.evanhoffman.bst.Node  - zebra is >= current node terrifying, checking right (if exists)
58 [main] DEBUG com.evanhoffman.bst.Node  - zebra is >= current node tomatoes, checking right (if exists)
58 [main] DEBUG com.evanhoffman.bst.Node  - zebra is >= current node unusable, checking right (if exists)
58 [main] DEBUG com.evanhoffman.bst.Node  - zebra is >= current node vertical, checking right (if exists)
58 [main] DEBUG com.evanhoffman.bst.Node  - zebra is >= current node warmed, checking right (if exists)
58 [main] DEBUG com.evanhoffman.bst.Node  - zebra is >= current node whence, checking right (if exists)
58 [main] DEBUG com.evanhoffman.bst.Node  - zebra is >= current node wrecked, checking right (if exists)
58 [main] INFO com.evanhoffman.bst.StringBstBuilder  - max word: wrecked

Recently had someone ask me to solve this problem: assume you have a list of objects, some of which may be lists of arbitrary depths. Write a function to return the list “flattened,” so sublists are all in the “main” list. I solved it recursively pretty easily, but it took some thought to do it without recursion. My solutions are below.

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package com.evanhoffman.listflattener;
 
import java.util.LinkedList;
import java.util.List;
import java.util.ListIterator;
 
import org.apache.log4j.BasicConfigurator;
import org.apache.log4j.Logger;
 
public class ListFlattener {
 
        private static Logger logger = Logger.getLogger(ListFlattener.class);
 
        public static List<Object> flattenList(List<Object> inList) {
                List<Object> newList = new LinkedList<Object>();
 
                for (Object i : inList) {
                        // If it's not a list, just add it to the return list.
                        if (!(i instanceof List)) {
                                newList.add(i);
                        } else {
                                // It's a list, so add each item to the return list.
                                newList.addAll(flattenList((List<Object>)i));
                        }
                }
 
                return newList;
        }
 
        public static List<Object> flattenListNoRecursion(List<Object> inList) {
                List<Object> tempList = null;
 
                // Clone the input list to newList
                List<Object> newList = new LinkedList<Object>();
                newList.addAll(inList);
 
                ListIterator<Object> iterator = newList.listIterator();
 
 
                int currentPosition = 0;
 
                while (iterator.hasNext()) {
                        Object i = iterator.next();
                        if (!(i instanceof List)) {
                                // If it's not a list, advance the position.  Don't advance position if this IS a list.
                                currentPosition++;
                        } else {
                                // If the current item is a list, save it to a temp var.
                                tempList = (List<Object>) i;
 
                                // Delete the list from the list
                                iterator.remove();
 
                                // Add each item from the temp list to the master list at the same position the sublist was removed.
                                for (Object obj : tempList) {
                                        iterator.add(obj);
                                }
 
                                // reset the iterator to re-walk the list that was just inserted (within the master) to check for more lists.
                                iterator = newList.listIterator(currentPosition);
                        }
                }
                return newList;
        }
 
        public static void printList(List<Object> list) {
                int i = 0;
                for (Object item : list) {
                        logger.debug("List item #"+i +": "+item);
                        i++;
                }
        }
 
        public static void main(String[] args) {
 
                BasicConfigurator.configure();
 
                // List of strings
                LinkedList<String> stringList = new LinkedList<String>();
                for (Integer i = 0; i < 10; i++) {
                        stringList.add("String #" +i.toString());
                }
 
                // List of integers
                LinkedList<Integer> intList = new LinkedList<Integer>();
                for (Integer i = 10; i < 20; i++) {
                        intList.add(i);
                }
 
                // Nested Lists
                LinkedList<Object> nestedList1 = new LinkedList<Object>();
                LinkedList<Object> nestedList2 = new LinkedList<Object>();
                LinkedList<String> nestedList3 = new LinkedList<String>();
 
                nestedList3.add("Nested String 1");
                nestedList3.add("Nested String 2");
                nestedList2.add(nestedList3);
                nestedList1.add(nestedList2);
 
                LinkedList<Object> bigList = new LinkedList<Object>();
 
                bigList.add("First item");
                bigList.add(stringList);
                bigList.add("Third Item");
                bigList.add(intList);
                bigList.add("Fifth Item");
                bigList.add(nestedList1);
                bigList.add("Seventh Item");
 
//              List<Object> flattenedList = flattenList(bigList);
                List<Object> flattenedListRecursion = flattenList(bigList);
                List<Object> flattenedList = flattenListNoRecursion(bigList);
 
                logger.debug("Original list:                 "+bigList.toString());
//              printList(bigList);
                logger.debug("Flattened list (w/ recursion): "+flattenedListRecursion.toString());
                logger.debug("Flattened list (no recursion): "+flattenedList.toString());
//              printList(flattenedList);
 
        }
}

I’m giddy! I found this post on mozdev.org which was magical.

[evan@ehoffman ~]$ java -version
java version "1.6.0_17"
Java(TM) SE Runtime Environment (build 1.6.0_17-b04)
Java HotSpot(TM) 64-Bit Server VM (build 14.3-b01, mixed mode)

[root@ehoffman plugins]# uname -a
Linux ehoffman 2.6.30.8-64.fc11.x86_64 #1 SMP Fri Sep 25 04:43:32 EDT 2009 x86_64 x86_64 x86_64 GNU/Linux
[root@ehoffman plugins]# pwd
/usr/lib64/mozilla/plugins
[root@ehoffman plugins]# ln -s /usr/java/jdk1.6.0_16/jre/lib/amd64/libnpjp2.so

The main thing I was missing was that the plugin isn’t libpluginjava_oji.so, or whatever I thought it was, but libnpjp2.so. Once I created the symlink into /usr/lib64/mozilla/plugins it worked (as verified on http://www.java.com/en/download/help/testvm.xml and http://www.java.com/en/download/installed.jsp).

That’s all it takes to get the Sun Java plugin working in Firefox on Linux.

I wrote a thing to calculate compound interest and print out how much you’ve accrued after each period. It’s pretty basic but I was bored and didn’t want to do it via calculator. The code is in InterestCalculator.java, sample output is below:

Initial principal: 5000.00
Interest rate:     0.05 (4.93%)
# of ann. periods: 4
Total years:       5
Annual Addition:   500.0
Starting year 1 with $5000.00
Year 1, period 1, accrued $61.62, value is now: $5061.62
Year 1, period 2, accrued $62.38, value is now: $5124.01
Year 1, period 3, accrued $63.15, value is now: $5187.16
Year 1, period 4, accrued $63.93, value is now: $5251.09
Added $500.00 for the end of year 1, total is now: 5751.09
Starting year 2 with $5751.09
Year 2, period 1, accrued $70.88, value is now: $5821.98
Year 2, period 2, accrued $71.76, value is now: $5893.73
Year 2, period 3, accrued $72.64, value is now: $5966.37
Year 2, period 4, accrued $73.54, value is now: $6039.91
Added $500.00 for the end of year 2, total is now: 6539.91
Starting year 3 with $6539.91
Year 3, period 1, accrued $80.60, value is now: $6620.51
Year 3, period 2, accrued $81.60, value is now: $6702.11
Year 3, period 3, accrued $82.60, value is now: $6784.71
Year 3, period 4, accrued $83.62, value is now: $6868.34
Added $500.00 for the end of year 3, total is now: 7368.34
Starting year 4 with $7368.34
Year 4, period 1, accrued $90.81, value is now: $7459.15
Year 4, period 2, accrued $91.93, value is now: $7551.08
Year 4, period 3, accrued $93.07, value is now: $7644.15
Year 4, period 4, accrued $94.21, value is now: $7738.37
Added $500.00 for the end of year 4, total is now: 8238.37
Starting year 5 with $8238.37
Year 5, period 1, accrued $101.54, value is now: $8339.90
Year 5, period 2, accrued $102.79, value is now: $8442.69
Year 5, period 3, accrued $104.06, value is now: $8546.75
Year 5, period 4, accrued $105.34, value is now: $8652.09
Added $500.00 for the end of year 5, total is now: 9152.09
Final value: $9152.09

Edit: I’ve moved this code to github (https://github.com/evandhoffman/JPEG-Organizer). I recently modified it so it won’t move duplicate files – if you have a file named IMG_0012.JPG in the target directory already, it will calculate the SHA-1 sum of the source & target files. If the files have the same hash (i.e., they’re identical files) it won’t copy the duplicate over. If they hash differently, it will still copy the new file as IMG_0012.JPG.001 (or whatever).

Edit 2: I just realized that the old links to the code didn’t work (apparently since I moved to JustHost) so I’ve deleted them.

I wrote a little utility to reorganize my digital camera pics based on the EXIF date-taken data stored in the pic. It’s pretty simple, I hacked it together in about an hour,
but I thought it might be worth sharing for anyone else looking to do something similar. My camera organizes stuff as it sees fit sometimes, I am particular about my directory structure. This is probably a job best left to perl, but I don’t feel like getting Perl running on my Windows box where all the pics are. Now I can finally burn all my images to DVD.