Thursday, February 14, 2013

Java - String comparison

Does it give you a bellyache?
Never mind, you can compare them like this-

System.out.println(gg1.compareTo(gg3));

Saturday, February 9, 2013

Url encode an HTTP GET Solr request and parse json using gson java library

Make a request to the SOLR webserver and parse the json string to Java classes using the code snippets below.
The JSON to be parsed- The corresponding Java classes- Code snippet to make a web server call and parse using gson-

The Java classes must have the same variable names as the Json's keys. Notice how nested Json elements are handled.

Wednesday, February 6, 2013

Errors running builder 'Google WebApp Project Validator'

Error:

Problems occurred building the selected resources.
Errors running builder 'Java Builder' on project 'curve_app'.
com/google/gdt/eclipse/suite/preferences/GdtPreferences
Errors running builder 'Google WebApp Project Validator' on project 'curve_app'.
java.lang.NullPointerException

Workaround solution:

Close all projects, close eclipse.

Start eclipse using, "eclipse -clean" option.

You can try repeating the process 2-3 times,  if it does not work first time.

Not sure of the exact reason why this appears.


Tuesday, February 5, 2013

Highcharts Phantomjs Export - TypeError: 'undefined' is not an object

Generating a png file from config-

phantomjs-1.8.1/bin/phantomjs highcharts-convert.js -infile config.json  -outfile out1.png -width 300 -scale 2.5 -constr Chart -callback callback.js

Error-

Things to check-
1. The following 3 files should be there in same folder or you have to set the paths to these here-
var config = {
                /* define locations of mandatory javascript files */
                HIGHCHARTS: 'highstock.js',
                HIGHCHARTS_MORE: 'highcharts-more',
                JQUERY: 'jquery-1.8.2.min.js'
        },

2. The 'infile' parameter should have an extension of .json, because that is what it uses to decide between svg input and a configuration json.

Friday, February 1, 2013

Monday, January 21, 2013

Hadoop - OutOfMemoryError: Java heap space

I was writing a hadoop job which processes many files and creates multiple files from each file. I was using "MultipleOutputs" to write them. It worked fine for a small number of files but I was getting the following error for large number of files. I tried increasing the ulimit and -Xmx but to no avail.

2013-01-15 13:44:05,154 FATAL org.apache.hadoop.mapred.Child: Error running child : java.lang.OutOfMemoryError: Java heap space
    at org.apache.hadoop.hdfs.DFSOutputStream$Packet.(DFSOutputStream.java:201)
    at org.apache.hadoop.hdfs.DFSOutputStream.writeChunk(DFSOutputStream.java:1423)
    at org.apache.hadoop.fs.FSOutputSummer.writeChecksumChunk(FSOutputSummer.java:161)
    at org.apache.hadoop.fs.FSOutputSummer.flushBuffer(FSOutputSummer.java:136)
    at org.apache.hadoop.fs.FSOutputSummer.flushBuffer(FSOutputSummer.java:125)
    at org.apache.hadoop.fs.FSOutputSummer.write1(FSOutputSummer.java:116)
    at org.apache.hadoop.fs.FSOutputSummer.write(FSOutputSummer.java:90)
    at org.apache.hadoop.fs.FSDataOutputStream$PositionCache.write(FSDataOutputStream.java:54)
    at java.io.DataOutputStream.write(DataOutputStream.java:90)
    at org.apache.hadoop.mapreduce.lib.output.TextOutputFormat$LineRecordWriter. writeObject( TextOutputFormat.java:78)
    at org.apache.hadoop.mapreduce.lib.output.TextOutputFormat$LineRecordWriter. write(TextOutputFormat.java:99)
    **at org.apache.hadoop.mapreduce.lib.output.MultipleOutputs.write( MultipleOutputs.java:386)
    at com.demoapp.collector.MPReducer.reduce(MPReducer.java:298)
    at com.demoapp.collector.MPReducer.reduce(MPReducer.java:28)**
    at org.apache.hadoop.mapreduce.Reducer.run(Reducer.java:164)
    at org.apache.hadoop.mapred.ReduceTask.runNewReducer(ReduceTask.java:595)
    at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:433)
    at org.apache.hadoop.mapred.Child$4.run(Child.java:268)
    at java.security.AccessController.doPrivileged(Native Method)
    at javax.security.auth.Subject.doAs(Subject.java:396)
    at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1332)
    at org.apache.hadoop.mapred.Child.main(Child.java:262)


Solution:
I used the following configuration values to resolve it-
OPTS="-Dmapred.reduce.tasks=8 -Dio.sort.mb=640 -Dmapred.task.timeout=1200000"
hadoop jar ${JAR} ${OPTS} -src ${SRC} -dest ${DST}









Tuesday, September 25, 2012

iOS 6 - Apple maps needs to find a shorter route to the correct destination

We all have heard a lot about Apple Maps lately. The verdict is already out. A forgettable job by Apple. The last full update(Iphone 4) had the dropped signal issue and now it is the maps. I usually don't like to get involved in the Apple/Android war but this was one incident, I couldn't resist writing about.
Yes, I have an iPhone. It is an iPhone 4 and I recently updated to iOS 6. I am on AT&T and want to move to T-mobile. I am eligible for an upgrade but I will skip the upgrade this time for reasons I would like to keep out of this blog entry. So on a Sunday morning, when I am finished buying groceries at the nearby Lucky's, the first thing I do is search for a T-mobile store on my new Apple maps and this is what it shows-



So I start driving and I find another Lucky's supermarket at my destination and no T-mobile store anywhere close. That was such a shame.

So tried to search for the same route from Google maps and this is what I get-

Interestingly, the place is in an opposite direction all together.
Then I tried to move the destination pin to the location where Apple maps was locating the T-mobile store and this is what I get-


So it looks like there is not a problem with locating the address alone, but also the route taken. Google maps takes me via a simpler route- a U turn and a right turn but Apple maps goes through a series of twists and turns, getting on the highway, changing lanes etc. The route by Google maps is also shorter 3.2 miles (to the wrong destination of course)

I am not an expert, but I guess Apple needs to map the correct co-ordinates to the expected destination and also debug those algorithms for shortest route possible. It will be a while before I trust Apple maps. Meanwhile, I will use my secondary phone, Nokia N8 for my navigation needs.

On a side note, Nokia 920 does sound appealing to me.