simple Java Set/Map initialization

Nikolaus Gradwohl2008-04-20T07:55:00+02:00

When you need a array in java filled with some data, initializing it is easy

String[] bla = new String[] { "Foo", "Bar", "Bla" };

and done. but when you need a Map or a Set prefilled with some data it starts getting complicated. you can either use a static initializer block like

public class Bla {
    static Set<String> dings;
    static {
        dings = new HashSet<String>();
        dings.add("foo");
        dings.add("bla");
    }
}

or you fill your set or map in the contructor if it is still null (be carefull if you use this in a multithreaded application)

another way i have learnd at the last jax is using this code

public class Bla {
    static Set<String> dings = new HashSet<String>() {{ 
        add("Foo"); add("Bar"); add("Bla"); }};
}

neat isn't it?

this also works with a Map

public class Bla {
    static Map<String,String> dings = new HashMap<String,String>() {{ 
        put("k1", "Foo"); put("k2", "Bar"); put("k2", "Bla"); }};
}
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Typo Update

Nikolaus Gradwohl2008-04-10T07:32:00+02:00

I recently updated my blog to the latest shiny blinking bleeding edge "typo version":http://www.typosphere.org the updates really went very smooth and my nagios tells me that the stability has improved very much :-)

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download bots

Nikolaus Gradwohl2008-03-15T17:13:00+01:00

UPDATE: I posted some building instructions for Download-Bots

i just started a lengthy download and had to kill some time so i started to build some toy-robots for my kids.

it took me aproxymatly 90 mb to build 2 robots

so while downloading my next ubuntu cd 1 could build 12 of them and while downloading the iphone sdk i could make another 48! An army of little robots! World donimation! muaaahahaha!

bots

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Rfid-Reader (part2)

Nikolaus Gradwohl2008-01-18T22:23:00+01:00

due high public demand ( i have a reader! ) i post a photo of my rfid-reader. The small black dot on the plastic-disk surrounded by copper-wire is the actual rfid-transponder chip - awsome

RFID-Reader

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Multicard setup with freevo

Nikolaus Gradwohl2008-01-15T07:07:00+01:00

I'm using freevo for my vdr and like it very much. Recently in austria terestrial analog tv has bin turned off and everyone had to switch to DVB. So our block got a big Satelite-Receiver and a box that transcodes the DBV-S signal to DBV-C. and i hat to put a DVB-C card in my freevo box ...

to "make the hunt more interessting (shirkan - the jungle-book)" some of the channels still come over analog-tv. freevo handles mulit-card setups very well, but only if the cards are the same type. So i had to patch it a little to support my setup where some channels have to be recorded and viewed from one card and some from the other.

i extended the 'VideoGroup' class by a "vcr_cmd" member, and wrote a little record-pluin that sets the command depending on the channel description

VIDEO_GROUPS = [
    VideoGroup(vdev='/dev/video0',
            adev=None,
            input_type='tuner',
            input_num=0,
            tuner_norm='pal',
            tuner_chanlist='europe-west',
            desc='Default Video Group',
            group_type='ivtv',
            record_group=None,
            vcr_cmd='/usr/local/bin/ivtv-record.py %(filename)s %(channel)s %(seconds)s',
      ),
    VideoGroup(
            vdev='/dev/video0',
            adev=None,
            input_type='tuner',
            input_num=0,
            desc='DVB Viewer',
            group_type='dvb',
            record_group=None,
            vcr_cmd = 'mencoder -oac copy -ovc copy -o %(filename)s -dvbin card=1
                            "dvb://%(channel)s" -endpos %(seconds)s'
      )
    ]

ivtv-record is a small script i have written because i cant use the ivtv plugin anymore (it doesnt use the cmd variables). my record-plugin is a extenion to the "generic-record.py" where i changed the line 'self.rec_command = config.VCR_CMD % cl_options' to 'self.rec_command = vg.vcr_cmd % cl_options'

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network environments

Nikolaus Gradwohl2008-01-15T06:45:00+01:00

i have a new version of my "detect where i am" script that workes absolutly hands free. i rarely turn my mac off, most of the times it stayes in sleep mode when im traveling from one site to another.

so i use "SleepWatcher" a great tool from Bernhard Baehr to trigger a script that scanns for known wlans and changes my proxy settings

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RFID-Reader

Nikolaus Gradwohl2007-12-12T22:38:00+01:00

I got my RFID-Reader 2 plus from conrad running!!! it took me just 5 months to find out what "stabilized 5V+" means :-)

the reader can be configured to send all the id strings it reads. but unless a barcode reader, it isnt triggerd by the user but sends the strings it finds all the time like crazy - looks cool in a terminal program :-) is also fun to see which tags are read if more than one is in the reading distance - maybe i make a game out of that :-)

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PDF for N770

Nikolaus Gradwohl2007-12-07T06:42:00+01:00

I own a Nokia 770 which i use to read pdf-files in the subway. i realy like it, but it has one downside - it is extreamly slow in changing the page if the page has to be zoomed or scrolled. the solution i found was to define a custom papersize for my "print-to-pdf" dialog, which fits into my N770 screen without the need to scroll or zoom.

if i want to read some website-content offline in the subway, i just have to print it to pdf using my custom page-format and copy it to my device using bluetooth.

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automatic proxy configuration in firefox

Nikolaus Gradwohl2007-11-03T15:43:00+01:00

In an erlier article i describe how to switch between the network environments i am using, but there was one programm i could not convince to let me change the proxy settings via apple script - firefox.

i still needet to switch the firefox settings per hand - something i didnt like at all.

one day the little "fetch proxy settings for url" dialog part from the firefox proxysettigns made me courious and i found out, that firefox expects a javascript file on this url, which tells firefox what proxy to use.

function FindProxyForURL(url, host) {
    if ( dnsResolve( host ) == "127.0.0.1" ) {
        return "DIRECT";
    } else {
        return "PROXY proxyhost:8080";
    }
}

this script can use some predefined functions like "isInNet" or "dnsResolve" to determine which network Im in and use the appropriate proxy. the file doesnt even have to live on a http server, a file:// url is sufficient.

e voila - no more manual proxy switching

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Using "functional"-Programming to map Resultsets to POJOs

Nikolaus Gradwohl2007-09-26T20:40:00+02:00

When I use jdbc to develop a small tool, where using a OR-Mapper like Hibernate is overkill, I always dislike that i have to dublicate all the "getStatement" "execQuery" "while (resultSet.next())" stuff.

i dont like to repeat stuff in my code. It would be very easy if java had closures, but i dont want to wait until java7 to simplify my code so I needet another idea.

java has no closures but it has something that can be used in a similar manner - Anonymous inner classes.

so to simplify the following class

Connection con = getConnection()
Statement st = con.createStatement();
ResultSet rs = st.executeQuery( "sqlstring");
List<Foo> result = new ArrayList<Foo>();
while (rs.next()) {
    Foo f = new Foo();
    f.setProperty1( rs.getString( "property1" ));
    f.setProperty2( rs.getString( "property2" ));
    result.add( f );
}
// imagine catch/finaly block here
st.close();
con.close();

i define a interface called Function

interface Function<T> {
    public T valueOf( ResultSet rs ) throws SQLException;
}

Then i define a QueryMapper like this

public class QueryMapper<T> {
    private Database db;
    public QueryMapper( Database db ) {
        this.db = db;
    }

    List<T> listOf( Function<T> f, String query ) {
        List<T> res = new ArrayList<T>();
        Resultset rs = ... get resultset for query ..
        while ( rs.next() ) {
            res.add( f.valueOf( rs ));
        }
        // catch/finaly block here
        return res;
    }
}

So all i have to do in my code now is calling

Function<Foo> fn = new Function<Foo>() {
    public Foo valueOf( ResultSet rs) throws SQLException {
        Foo res = new Foo();
        res.setPropery1( rs.getString( "property1" ));
        res.setPropery2( rs.getString( "property2" ));
        return res;
    }
}

QueryMapper<Foo> qm = QueryMapper<Foo>( db );
List<Foo> res = qm.listOf( fn, "select * from foo");

I can even recycle the Function objects ( if i query different object of the same type but with different ids for example ) thats more how i like it

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