Java Review: Tuesday, October 12, 2011

Java Run-time Exceptions

http://download.oracle.com/javase/1.4.2/docs/api/java/lang/IllegalStateException.html

• Class IllegalStateException
• example
• throw new IllegalStateException();
• use to catch programming development errors.
• exception should never occur unless there is a programming error.

http://download.oracle.com/javase/tutorial/essential/exceptions/throwing.html

• tutorial

http://download.oracle.com/javase/1.4.2/docs/api/java/lang/RuntimeException.html

• Class RuntimeException
• not checked
• not extra code
• danger of being a 'lazy programmer'

http://download.oracle.com/javase/tutorial/essential/exceptions/runtime.html

• can use to side step catch and specify requirements
• Runtime exceptions represent problems that are the result of programming problems
• If the client can reasonable be expected to recover from an exception, make it a checked exception

Garbage Collection in Java VMs

http://terracotta.org/products/bigmemory?asrc=eliminate-java-gc-tuning-2-gc-sno&gclid=CKzY28G346sCFcPt7Qod4kU9Rg

• Big memory
• works with
• JVMs
• HotSpot
• IBM JDK
• JRockit
• what about Dalvik?
• off-heap store
• not subject to Java GC
• Terracotta's tiered cache
• Enterprise Ehcache
• store up to a terabyte in the off-heap

http://www.koushikdutta.com/2009/01/dalvik-vs-mono.html

• Dalvik vs Mono

http://stackoverflow.com/questions/3078301/dalvik-memory-allocation-how-to-change-the-default-limits

• heap-limits set by OEM with Dalvik

http://pallergabor.uw.hu/androidblog/dalvik_opcodes.html

• Dalvik opcodes

http://mylifewithandroid.blogspot.com/2008/12/dalvik-opcodes.html

• DEX file format

http://mylifewithandroid.blogspot.com/2009/12/understanding-dalvik-bytecode-with.html

• Dalvik bytecode and Dedexer tool

http://en.wikipedia.org/wiki/Java_Virtual_Machine

• overview of Java VM

http://ryanolson.wordpress.com/2010/07/13/test-how-changing-the-max-amount-of-memory-per-vm-heap-can-effect-your-rom-cyanogen/

• Cyanogen allow Dalvik VM settings to be modified

http://blog.javia.org/android-allocation-free-code-avoids-the-gc-freeze/

• allocation-free code to avoid GC freeze

http://developer.android.com/guide/practices/design/performance.html

• Android, designing from performance

http://www.xinotes.org/notes/note/1449/

• heap size can be change in 'dx'
• example of changing

http://stackoverflow.com/questions/2298784/determine-when-the-android-gc-runs

• code to see the android GC run

http://stackoverflow.com/questions/1521317/is-it-possible-to-call-gc-in-android

• requesting GC
• System.gc();
• no guarantee it will run

Java Constants and Conditional Compile

http://www.javaworld.com/javaworld/javatips/jw-javatip5.html

• No textual preprocessor
• constants and conditional compilation
• use public static final boolean constant for  a regular if statement in regular code
• Have class using the constant interface implement the constant interface

Tech Review: Monday, October 10, 2011

C# null-coalescing operator

http://msdn.microsoft.com/en-us/library/ms173224.aspx

• From C# Reference for VS 2010
• example
• int? x = null;
• int y = x ?? -1;
• string s = null;
• Console.WriteLine (s ?? "Unspecified");
• used to define a default value for a nullable value type
• it returns the left-hand operand if it is not null; otherwise it returns the right operand

http://msdn.microsoft.com/en-us/library/1t3y8s4s.aspx

• more example from C# Programming Guide for VS 2010

http://stackoverflow.com/questions/278703/unique-ways-to-use-the-null-coalescing-operator

• not in Java, but some would like to add the feature

http://blog.joda.org/2009/01/java-7-null-default-and-null-safe_7527.html

• more about not in Java

http://www.merriam-webster.com/dictionary/coalescing

• coalescing mean "to grow together"
• does this sound like a good description of what the operator is doing?

Regions in Java

I know the above picture is not about 'Regions in Java' code, but it looked nice.

http://stackoverflow.com/questions/2344524/java-equivalent-to-region-in-c

• Basically, there are no region pre-compiler directives in Java
• There is support in some IDEs
• NetBeans
• // <editor-fold defaultstate="collapsed" desc="Your Fold Comment">
• ...
• // <editor-fold>
• Eclipse
• does it automatically for methods, imports, etc.
• Not declaration like in NetBeans
• Could you add one?
• Emacs?

Velocity Android 2.0 Internet Table 7" $100

http://www.tigerdirect.com/applications/searchtools/item-Details.asp?EdpNo=7188918&sku=V266-3032

• almost what I want
• missing the camera
• Multi touch capacitive screen

Viewsonic gTablet 10.1" Android 2.2:  $270

http://www.tigerdirect.com/applications/searchtools/item-Details.asp?EdpNo=7212231&sku=V18-0020

• This is what I want except the price and Android version

Simple C# Program

http://www.csharp-station.com/Tutorials/Lesson01.aspx

• the main routine starts with a Capital 'M' in C#
• starts with a lower case 'm' in Java

Listeners and Events (Actions) in Java

http://download.oracle.com/javase/tutorial/uiswing/events/index.html

• lesson on writing event listeners

http://download.oracle.com/javase/tutorial/uiswing/events/intro.html

• action listener
• public class Beeper ... implements ActionListener {
• adding an action listener to something
• button.addActionLisener ( new Beeper() )
• implement the method that does the action
• public void actionPerformed (ActionEvent e) {

http://download.oracle.com/javase/tutorial/uiswing/examples/events/BeeperProject/src/events/Beeper.java

• complete Beeper example

Java Color Map

http://www.ee.columbia.edu/~ronw/code/MEAPsoft/doc/html/ColorMap_8java-source.html

• color map in java
• Copyright
• Carnegie Mellon
• Sun
• Mitsubishi

Java List Interface and ArrayList Class

http://download.oracle.com/javase/6/docs/api/java/util/List.html

• Interface List <E>

http://download.oracle.com/javase/6/docs/api/java/util/ArrayList.html

• Class ArrayList<E>
• Example
• List list = Collections.synchronizedList (new ArrayList(...));

Java Collection Interface and Collections Class

http://download.oracle.com/javase/1,5.0/docs/api/java/util/Collection.html

• Interface Collection<E>

http://download.oracle.com/javase/1.4.2/docs/api/java/util/Collections.html

• static void sort (List list)
• reverse (List list)

Java Queue Interface and PriorityQueue Class

http://en.wikipedia.org/wiki/Queue_(abstract_data_type)

• new elements are put (enqueued) on the back of the queue
• element are pulled (dequeued) from the front of the queue
• First In First Out (FIFO)

http://download.oracle.com/javase/1,5.0/docs/api/java/util/Queue.html

• Interface Queue<E>
• offer (E o) // enqueue
• adds an element to the tail of the queue
• poll () // dequeue
• returns a removed element from the queue
• null is empty

http://download.oracle.com/javase/1,5.0/docs/api/java/util/PriorityQueue.html

• Class PriorityQueue<E>
• boolean add (E o)
• boolean offer (E o)
• E poll ()

Java Map Interface and HashMap Class

http://download.oracle.com/javase/tutorial/collections/interfaces/map.html

• tutorial

http://download.oracle.com/javase/6/docs/api/java/util/Map.html

• Interface Map<K,V>
• V put (K key, V value)
• V get (Object key)

http://download.oracle.com/javase/6/docs/api/java/util/HashMap.html

• Class HashMap<K,V>
• Example:
• Map m = Collections.synchronizedMap (new HashMap (...));

Chrome Remote Desktop

https://chrome.google.com/webstore/detail/gbchcmhmhahfdphkhkmpfmihenigjmpp

• BETA
• allow users to remotely access another computer through the Chrome browser or Chromebook
• An add on
• can easily miss the Icon after installation 

Tech Review: Wednesday, September 21, 2011

Working with porting C# to Java today.

Example of Java enums:  http://javahowto.blogspot.com/2008/04/java-enum-examples.html

• It is sort of like a class because you can override method inside the enum.
• @Override public String toString() {....}

Struct like objects in Java:  

• http://stackoverflow.com/questions/36701/struct-like-objects-in-java
• http://www.javacamp.org/javavscsharp/struct.html
• Java doesn't have structs
• in C# structs are:
• sealed (final)
• lightweight
• a value type, not a reference type (Object)
• more efficient than classes

Java vs. C# page: http://www.javacamp.org/javavscsharp/

• Has lots of really nice and clear comparisons.
• I need to read the whole thing

Benefits of using Final classes in Java:  http://www.java-tips.org/blog/java-se/benefits-of-using-final-class.html

• Control
• no one can inherit 
• final methods run faster than normal methods
• Java compiler may be able to inline a final method
• this link is suppose to dispute that
• http://www.ibm.com/developerworks/java/library/j-jtp1029.html
• 
  

Ternary or conditional operator in Java:  http://www.janeg.ca/scjp/oper/ternary.html

• operand1 ? operand2 : operand3;
• operand1 must be a boolean value or experssion

Operator overloading in Java:  http://stackoverflow.com/questions/77718/java-operator-overload

• program cannot overload operator like '+' or '-'
• http://www.velocityreviews.com/forums/t141181-operator-overloading-in-java.html
• JFront will take overload code and convert it to something Java can compile
• http://www.gginc.biz/jfront/index.html

The C# dictionary is similar to the Java Map interface:  

• http://download.oracle.com/javase/1.4.2/docs/api/java/util/Dictionary.html
• http://stackoverflow.com/questions/687942/java-map-equivalent-in-c
• Show going from Java Map to C# dictionary 
• description of Map interface
• http://download.oracle.com/javase/tutorial/collections/interfaces/map.html

The ArrayList Generic Class in Java:

• http://download.oracle.com/javase/6/docs/api/java/util/ArrayList.html
• Implements in List interface along with others
• not synchronized
• has an example of how to synchronize an ArrayList object

The C# ICollection interface:

• http://msdn.microsoft.com/en-us/library/92t2ye13.aspx
• seems similar to function of the Java Collection interface
• http://download.oracle.com/javase/6/docs/api/java/util/Collection.html

Another C#/Java comparison:  http://www.25hoursaday.com/CsharpVsJava.html#collections

A Java tutorial on collection interfaces:  

• http://download.oracle.com/javase/tutorial/collections/interfaces/
• http://download.oracle.com/javase/tutorial/collections/
• top of tutorial for collections

Today I was confused as to why code would compile in my simple command line program and not in Eclipse.

• Sometimes the error messages in Eclipse are miss leading
• I was trying to write code in the class body outside a method

Some examples of testing for null:  http://www.daniweb.com/software-development/java/threads/156111

• if (child == null) child = new Lista(c, null);

A tutorial on Eclipse:

• http://www.vogella.de/articles/Eclipse/article.html
• perspectives
• a visual container for a set of view and editors
• java
• debug
• C++?
• view and editors are grouped into
• views
• editors
• projects
• located in workspace
• workspace
• physical location of projects
• I thing Eclipse is more complex for many things that NetBeans.
• It's really an SDK, rather than an IDE (NetBeans)
• Seeing the error can be a pain in the neck
• http://stackoverflow.com/questions/1671115/how-to-detect-eclipse-compile-errors-java-jdt
• http://stackoverflow.com/questions/585642/eclipse-3-4-1-how-to-view-compiler-output-in-console-while-building-a-project
• The Eclipse JDT provides its own build-in Java compiler
• tightly integrated with Eclipse and JDT (Java Development Tools)
• http://www.eclipse.org/jdt/
• problems clearing 'Problems' window:  http://stackoverflow.com/questions/2385402/eclipse-cdt-how-to-clear-problems-window-without-invoking-clean-project-or-build
• tried what was recommended, but it didn't work
• no good solution given

Comparing Java and C# Generics:  http://www.jprl.com/Blog/archive/development/2007/Aug-31.html

Java Properties and C# properties are not the same thing at all:  http://download.oracle.com/javase/1.4.2/docs/api/java/util/Properties.html

• C# properties are a value in the object
• Java properties are a way of saving the state to a file and reading it back

Another very nice Java/C# Comparison:  http://www.harding.edu/fmccown/java_csharp_comparison.html

• This one would be best to read first

Java random number generation:

• generating a number in a range:
• http://stackoverflow.com/questions/363681/java-generating-random-number-in-a-range

In doing Repast Simphony development, the RandomHelper class should be used:

• Don't be confused by some of the descriptions of how to do random number in earlier versions of Repast
• Use the RandomHelper
• http://repast.sourceforge.net/docs/reference/SIM/Random%20Numbers.html
• http://repast.sourceforge.net/docs/api/repastjava/repast/simphony/random/RandomHelper.html#RandomHelper()
• RandomHelper has only static methods.
• encapsulates the colt library's random number generation
• Very complicated
• used a uniform distribution by default
• can use
• Beta
• Binomial
• ChiSquare
• etc
• Wraps "Colt":  http://acs.lbl.gov/software/colt/

A very nice example of a Java singleton implementation:  http://www.javaworld.com/javaworld/jw-04-2003/jw-0425-designpatterns.html

Default parameters in Java:

• http://stackoverflow.com/questions/965690/java-optional-parameters
• Doesn't really exist in Java
• http://stackoverflow.com/questions/997482/does-java-support-default-parameter-values
• can be done but is a bit ugly

Calling a constructor within a constructor in Java:  http://stackoverflow.com/questions/285177/how-do-i-call-one-constructor-from-another-in-java

• this(); //without a parameter

Java coding style:

• http://geosoft.no/development/javastyle.html#Naming Conventions
• methods begin in lower case

Declaring generic arrays:

• http://forums.techarena.in/software-development/1117589.htm
• HashMap <?,?> [] x = new HashMap <?,?>[3];
• this work but I could access 'x'
• Best to avoid and wrap in a list instead
• List<HashMap<Class, Class> x = new ArrayList<HashMap<Class1, Class2>(3);
• the above code may not be correct, but it has the idea

C# ArgumentException can be changed to a Java IllegalArgumentException:  https://forums.oracle.com/forums/thread.jspa?threadID=472866

Comparing Java and C# Generics:  http://www.jprl.com/Blog/archive/development/2007/Aug-31.html

• performance advantages in C#

For each Loop in Java:

• http://download.oracle.com/javase/1,5.0/docs/guide/language/foreach.html
• for (List item : arrayList) { }

Generics and array construction in Java:

• http://stackoverflow.com/questions/217065/cannot-create-an-array-of-linkedlists-in-java
• is broken

Comparison between Java HashMap and .NET Hastable:  http://www.microsoft.com/mspress/books/sampchap/6173.aspx#116

Sorting a collection in Java: http://stackoverflow.com/questions/740299/how-do-i-sort-a-set-in-java

• List myList = new ArrayList (collection);
• Collections.sort (mylist);

Repast Simphony Projections

• Interface Projection
• http://repast.sourceforge.net/docs/api/repastjava/repast/simphony/space/projection/Projection.html
• interface ContinuousSpace
• AbstractContinuousSpace
• ContextPhysics
• ContextSpace
• DefaultContinuousSpace 
• DefaultPhysicsSpace
• Projected3DSpace
• interface Geography
• ContextGeography
• DefaultGeography
• interface Grid
• AbstractGrid, 
• ContextFastSingleGrid, 
• ContextGrid, 
• DefaultGrid, 
• FastDenseSingleOccuGrid, 
• Projected3DGrid
• interface NetWork
• ContextJungNetwork, 
• DirectedJungNetwork, 
• JungNetwork, 
• UndirectedJungNetwork
• interface PysicsSpace
• ContextPhysics
• DefaultPhysicsSpace
• Implementing Classes
• Abstract
1. AbstractContinuousSpace, 
2. AbstractGrid, 
• Concrete 
1. ContextFastSingleGrid, 
2. ContextGeography, 
3. ContextGrid, 
4. ContextJungNetwork, 
5. ContextPhysics, 
6. ContextSpace, 
7. DefaultContinuousSpace, 
8. DefaultGeography, 
9. DefaultGrid, 
10. DefaultPhysicsSpace, 
11. DefaultProjection, 
12. DirectedJungNetwork, 
13. FastDenseSingleOccuGrid, 
14. JungNetwork, 
15. Projected3DGrid, 
16. Projected3DSpace, 
17. UndirectedJungNetwork

Calling C Code from Java

http://www.mactech.com/articles/mactech/Vol.13/13.09/CallingCCodefromJava/index.html

• Example and discussion.
• dated

Java Buffered Reader

http://download.oracle.com/javase/6/docs/api/java/io/BufferedReader.html

• import java.io.BufferedReader;
• BufferedReader in = new BufferedReader(new FileReader("filename"));

How Do I Include a Class

If the class is not in a package, simple put the compiled class file in the same directory and the class you are compiling.

If the class is in a package, build a directory structure beneight the directory of the file you are trying to compile that mirrors the package structure.