Uno scrittoio digitale …

21 maggio 2015

Appunti

Archiviato in: Senza categoria — admin @ 20:38

http://stackoverflow.com/questions/74674/how-to-do-i-check-cpu-and-memory-usage-in-java

http://www.vogella.com/tutorials/JavaPerformance/article.html

http://javatune.com/post.cfm/15-useful-performance-tools-for-java-environments

http://docs.oracle.com/javase/7/docs/platform/jvmti/jvmti.html

MapDB (java library)

Archiviato in: java — Tag:, , , — admin @ 20:24

MapDB is embedded database engine. It provides java collections backed by disk or memory database store. MapDB has excellent performance comparable to java.util.HashMap and other collections, but is not limited by GC. It is also very flexible engine with many storage backend, cache algorithms, and so on. And finally MapDB is pure-java single 400K JAR and only depends on JRE 6+ or Android 2.1+.

What for?
> In-memory cache with expiration based on time-to-live or maximal size, Redis or EZCache replacement
> Huge indexes
> Persistent data model
> Alternative memory model if you are limited by GC

6 maggio 2015

caniuse html5/css3 feature ?

Archiviato in: Senza categoria — Tag:, — admin @ 09:21

http://caniuse.com/

Grazie Giada D. :D

28 aprile 2015

Ninna nanna per Lorenzo

Archiviato in: Senza categoria — Tag: — admin @ 22:09

ninna nanna

21 aprile 2015

Java7 ForkJoin Framework

Archiviato in: Senza categoria — Tag:, , — admin @ 11:17

For learning about basic parallel operations, there are only 2-4 classes you need to know about:

  • ForkJoinPool: you create exactly one of these to run all your fork-join tasks in the whole program
  • RecursiveTask: you run a subclass of this in a pool and have it return a result; see the examples below
  • RecursiveAction: just like RecursiveTask except it does not return a result
  • ForkJoinTask: superclass of RecursiveTask and RecursiveAction. fork and join are methods defined in this class. You won’t use this class directly, but it is the class with most of the useful javadoc documentation, in case you want to learn about additional methods

import java.util.Random;
import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.RecursiveTask;

public class MaximumFinder extends RecursiveTask {

  private static final int SEQUENTIAL_THRESHOLD = 5;

  private final int[] data;
  private final int start;
  private final int end;

  public MaximumFinder(int[] data, int start, int end) {
    this.data = data;
    this.start = start;
    this.end = end;
  }

  public MaximumFinder(int[] data) {
    this(data, 0, data.length);
  }

  @Override
  protected Integer compute() {
    final int length = end - start;
    if (length < SEQUENTIAL_THRESHOLD) {
      return computeDirectly();
    }
    final int split = length / 2;
    final MaximumFinder left = new MaximumFinder(data, start, start + split);
    left.fork();
    final MaximumFinder right = new MaximumFinder(data, start + split, end);
    return Math.max(right.compute(), left.join());
  }

  private Integer computeDirectly() {
    System.out.println(Thread.currentThread() + ' computing: ' + start
                       + ' to ' + end);
    int max = Integer.MIN_VALUE;
    for (int i = start; i < end; i++) {
      if (data[i] > max) {
        max = data[i];
      }
    }
    return max;
  }

  public static void main(String[] args) {
    // create a random data set
    final int[] data = new int[1000];
    final Random random = new Random();
    for (int i = 0; i < data.length; i++) {
      data[i] = random.nextInt(100);
    }

    // submit the task to the pool
    final ForkJoinPool pool = new ForkJoinPool(4);
    final MaximumFinder finder = new MaximumFinder(data);
    System.out.println(pool.invoke(finder));
  }
}

19 aprile 2015

Measure Anything, Measure Everything

Archiviato in: code — Tag:, — admin @ 16:01

statsd

13 aprile 2015

Run your code online

Archiviato in: code — Tag: — admin @ 10:14

http://runnable.com/

Fatto veramente bene e molto semplice da usare.

19 gennaio 2015

Css

Archiviato in: sapere è potere — admin @ 19:35

purecss
css rule

da rivedere … :D (grazie Giada D.)

16 gennaio 2015

pancake più buoni del mondo

Archiviato in: sapere è potere — admin @ 22:33

primo
secondo

Ottimi entrambi … :D

15 gennaio 2015

A Visual Explanation of SQL Joins

Archiviato in: code — Tag:, — admin @ 18:36

Visto che me le scordo sempre … qua c’è un modo visuale per ricordarsi delle diverse JOIN.

JPA 2.*

Archiviato in: code, java — admin @ 00:41

Solo qualche link utile … a capirci qualcosa :D

guice and jpa
example
wiki

31 dicembre 2014

Clean/flush DNS Cache in linux

Archiviato in: sapere è potere — Tag: — admin @ 14:08

qua

30 dicembre 2014

Rest Principles

Archiviato in: Senza categoria — Tag:, — admin @ 11:49

slide 10 on http://www.slideshare.net/dmytro-chyzhykov/making-java-rest-with-jaxrs-20

GET     /questions          index       list of questions
GET     /questions/new      new         show new question form
POST    /questions          create      create a new question
GET     /questions/:id      show        show a specific question
GET     /questions/:id/edit edit        show form to edit question
PUT     /questions/:id      update      update a specific question
DELETE  /questions/:id      destroy     delete a specific question

27 dicembre 2014

jGroups

Archiviato in: java — Tag:, — admin @ 17:25

qua

JGroups is a toolkit for reliable messaging. It can be used to create clusters whose nodes can send messages to each other. The main features include

> Cluster creation and deletion. Cluster nodes can be spread across LANs or WANs
> Joining and leaving of clusters
> Membership detection and notification about joined/left/crashed cluster nodes
> Detection and removal of crashed nodes
> Sending and receiving of node-to-cluster messages (point-to-multipoint)
> Sending and receiving of node-to-node messages (point-to-point)

27 novembre 2014

Css Layout

Archiviato in: sapere è potere — Tag:, , — admin @ 16:06

here

20 novembre 2014

Force Element To Self-Clear its Children

Archiviato in: sapere è potere — Tag: — admin @ 20:00
.clearfix:after {
     visibility: hidden;
     display: block;
     font-size: 0;
     content: " ";
     clear: both;
     height: 0;
}

Just apply a class=”clearfix” to the parent element.

original page are available here

12 novembre 2014

Martin Fowler

Archiviato in: sapere è potere — admin @ 22:34

here and his websites

6 novembre 2014

Ruby on Rails application server solution

Archiviato in: code, rails — Tag:, — admin @ 17:24

Giusto qualche link utile per capire le alternative:

phusion-passenger-for-dummies
ruby-on-rails-server-options
rack

26 ottobre 2014

Come installare Popcorn Time su Ubuntu

Archiviato in: ubuntu — Tag:, — admin @ 13:15

$> sudo add-apt-repository ppa:webupd8team/popcorntime
$> sudo apt-get update
$> sudo apt-get install popcorn-time

10 ottobre 2014

How to revert (roll back) to a previous revision with Subversion

Archiviato in: sapere è potere — Tag: — admin @ 17:46

> svn merge –dry-run -r:73:68 http://my.repository.com/my/project/trunk
> svn merge -r:73:68 http://my.repository.com/my/project/trunk
> svn commit -m “Reverted to revision 68.”

If you want to see exactly what changes will be applied, do a diff:

> svn diff -r:73:68 http://my.repository.com/my/project/trunk

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