Develop Reference

Parsing Serialized Java objects in Python

The string at the bottom of this post is the serialization of a java.util.GregorianCalendar object in Java. I am hoping to parse it in Python.
I figured I could approach this problem with a combination of regexps and key=val splitting, i.e. something along the lines of:
text_inside_brackets = re.search(r"\[(.*)\]", text).group(1)
and
import parse
for x in [parse('{key} = {value}', x) for x in text_inside_brackets.split('=')]:
my_dict[x['key']] = x['value']
My question is: What would be a more principled / robust approach to do this? Are there any Python parsers for serialized Java objects that I could use for this problem? (do such things exist?). What other alternatives do I have?
My hope is to ultimately parse this in JSON or nested Python dictionaries, so that I can manipulate it it any way I want.
Note: I would prefer to avoid a solution relies on Py4J mostly because it requires setting up a server and a client, and I am hoping to do this within a single
Python script.
java.util.GregorianCalendar[time=1413172803113,areFieldsSet=true,areAllFieldsSet=true,lenient=true,zone=sun.util.calendar.ZoneInfo[id="America/New_York",offset=-18000000,dstSavings=3600000,useDaylight=true,transitions=235,lastRule=java.util.SimpleTimeZone[id=America/New_York,offset=-18000000,dstSavings=3600000,useDaylight=true,startYear=0,startMode=3,startMonth=2,startDay=8,startDayOfWeek=1,startTime=7200000,startTimeMode=0,endMode=3,endMonth=10,endDay=1,endDayOfWeek=1,endTime=7200000,endTimeMode=0]],firstDayOfWeek=1,minimalDaysInFirstWeek=1,ERA=1,YEAR=2014,MONTH=9,WEEK_OF_YEAR=42,WEEK_OF_MONTH=3,DAY_OF_MONTH=13,DAY_OF_YEAR=286,DAY_OF_WEEK=2,DAY_OF_WEEK_IN_MONTH=2,AM_PM=0,HOUR=0,HOUR_OF_DAY=0,MINUTE=0,SECOND=3,MILLISECOND=113,ZONE_OFFSET=-18000000,DST_OFFSET=3600000]

The serialized form of a GregorianCalendar object contains quite a lot of redundancy. In fact, there are only two fields that matter, if you want to reconstitute it:
the time
the timezone
There is code for extracting this in How to convert Gregorian string to Gregorian Calendar?
If you want a more principled and robust approach, I echo mbatchkarov's suggestion to use JSON.

How do I add the new currency code to Java?

The Chinese currency has the ISO 4217 code CNY. Since free global trading in that currency is restricted though, there's a second 'offshore' currency equivalent, called CNH. Wikipedia has a bit of summary of this all.
CNH isn't in ISO 4217, but I'd like to be able to use it in my app without having to write my own Currency class. Presumably there's some kind of list somewhere inside the JVM install. How do I go about adding additional currency codes?
EDIT: See this question for dealing with this in Java 7

Looks like support for this was added with Java 7.
For earlier versions, you could use an equivalent Currency class of your own devising, or less happily, replace the default java.util.Currency class (or java.util.CurrencyData, which contains the raw data) in your classpath (whitepaper).

BigDecimal notation eclipse plugin or nice external tool

I need to make a lot of operations using BigDecimal, and I found having to express
Double a = b - c * d; //natural way
as
BigDecimal a = b.subtract(c.multiply(d))//BigDecimal way
is not only ugly, but a source of mistakes and communication problems between me and business analysts. They were perfectly able to read code with Doubles, but now they can't.
Of course a perfect solution will be java support for operator overloading, but since this not going to happen, I'm looking for an eclipse plugin or even an external tool that make an automatic conversion from "natural way" to "bigdecimal way".
I'm not trying to preprocess source code or dynamic translation or any complex thing, I just want something I can input text and get text, and keep the "natural way" as a comment in source code.
P.S.: I've found this incredible smart hack but I don't want to start doing bytecode manipulation. Maybe I can use that to create a Natural2BigDecimal translator, but I don't want to reinvent the wheel if someone has already done such a tool.
I don't want to switch to Scala/Groovy/JavaScript and I also can't, company rules forbid anything but java in server side code.

"I'm not trying to preprocess source code ... I just want something I can input [bigDecimal arithmetic expression] text".
Half of solving a problem is recognizing the problem for what it is. You exactly want something to preprocess your BigDecimal expressions to produce legal Java.
You have only two basic choices:
A stand-alone "domain specific language" and DSL compiler that accepts "standard" expressions and converts them directly to Java code. (This is one kind of preprocessor). This leaves you with the problem of keeping all the expression fragments around, and somehow knowing where to put them in the Java code.
A tool that reads the Java source text, finds such expressions, and converts them to BigDecimal in the text. I'd suggest something that let you code the expressions outside the actual code and inserted the translation.
Perhaps (stolen from another answer):
// BigDecimal a = b - c * d;
BigDecimal a = b.subtract( c.multiply( d ) );
with the meaning "compile the big decimal expression in the comment into its java equivalent, and replace the following statement with that translation.
To implement the second idea, you need a program transformation system, which can apply source-to-source rewriting rules to transforms (generate as a special case of transform) the code. This is just a preprocessor that is organized to be customizable to your needs.
Our DMS Software Reengineering Toolkit with its Java Front End could do this. You need a full Java parser to do that transformation part; you'll want name and type resolution so that you can parse/check the proposed expression for sanity.
While I agree that the as-is Java notation is ugly, and your proposal would make it prettier, my personal opinion is this isn't worth the effort. You end up with a dependency on a complex tool (yes, DMS is complex: manipulating code isn't easy) for a rather marginal gain.
If you and your team wrote thousands of these formulas, or the writers of such formulas were Java-naive it might make sense. In that case,
I'd go further, and simply insist you write the standard expression format where you need it. You could customize the Java Front End to detect when the operand types were of decimal type, and do the rewriting for you. Then you simply run this preprocessor before every Java compilation step.

I agree, it's very cumbersome! I use proper documentation (comments before each equation) as the best "solution" to this.
// a = b - c * d;
BigDecimal a = b.subtract( c.multiply( d ) )

You might go the route of an expression evaluator. There is a decent (albeit paid) one at http://www.singularsys.com/jep. Antlr has a rudimentary grammar that also does expression evaluation (tho I am not sure how it would perform) at http://www.antlr.org/wiki/display/ANTLR3/Expression+evaluator.
Neither would give you the compile-time safety you would have with true operators. You could also write the various algorithm-based classes in something like Scala, which does support operator overloading out of the box and would interoperate seamlessly with your other Java classes.

Java Unit conversion

I have a database table which stores the units name in full like liters, kilograms, milliliters, milligrams etc.. I need a library to recogonize these units and convert it to the unit I wish to. How do i do this ?
Code Logic:
I will read the unit "liters" from database and i wish to convert it to milli-liters so her the input is "20 liters" and output should be "20000 milli-liters"
I downloaded JScience library but i am not sure how to do this. please tel me how to use that or suggest any alternative. It would be better if you explain me with a code sample. Thanks!!

I'm inclined to say use Frink, but it does WAY more than you need here, although it does solve the problem
20 litres -> milliliters
//gives 20000
And it is just a cool little language. In java you'd have to run it like any other scripting library. The website has loads of info

I'm not aware that JScience provides a facility for parsing strings like "20 liters" (that spelling makes me cringe...), so you'll probably have to handle that yourself, by tokenizing the string into quantities and units.
Once you have that, you can use JScience to convert between units easily enough, although obviously converting from litres to milliltres is trivial. But in principle, it's something like:
Measure<Integer, Volume> input = Measure.valueOf(20, NonSI.LITRE);
Measure<Integer, Volume> output = input.to(SI.MILLI(NonSI.LITRE));
System.out.println(output);

Java simple String diff util

I'm looking for a simple java lib/src to highlight differences between two Strings, case-sensitive. A html output would be great, but I would be happy to get the indexes of the diffs, something like:
diff("abcd","aacd")
> [2,2]
diff("maniac", "brainiac")
> ["man",brain"] or [0,3] or something like that
The idea is to higlight typos or such in a swing program, since the input shold follow strict conventions.

Apache Commons Lang has a class called StringUtils which has both difference and indexOfDifference which fulfills your needs.
http://commons.apache.org/lang/
Check it out

The java-diff project might also be useful.
This is an implementation of the longest common subsequences (LCS) algorithm for Java. The Diff#diff() method returns a list of Difference objects, each of which describes an addition, a deletion, or a change between the two collections.