background preloader

JAVA

Facebook Twitter

Java Questions

CyclicBarrier. The java.util.concurrent.CyclicBarrier class is a synchronization mechanism that can synchronize threads progressing through some algorithm.

CyclicBarrier

In other words, it is a barrier that all threads must wait at, until all threads reach it, before any of the threads can continue. Here is a diagram illustrating that: The threads wait for each other by calling the await() method on the CyclicBarrier. Once N threads are waiting at the CyclicBarrier, all threads are released and can continue running. Creating a CyclicBarrier When you create a CyclicBarrier you specify how many threads are to wait at it, before releasing them. CyclicBarrier barrier = new CyclicBarrier(2); Waiting at a CyclicBarrier.

Unsafe

Java Cache. POI - EXCEL. JUnit. NIO. Java : different ways to filter a Collection - My name is Guido. Java : different ways to filter a Collection by Guido García on 29/10/2011 Imagine we have a simple Java class: And that you have a Collection of Person objects, such as the following one: How would you create a new Collection containing only men over 21?

Java : different ways to filter a Collection - My name is Guido

Use plain Java, like real men do Filtering by predicate The second option is what Commons Collections and Guava propose, and that I think should have been part of the Java core at least since Java 5. It remembers me the visitor pattern. I find it very similar to Python’s filter() function, but more verbose due to Java’s nature. This way your code becomes cleaner, and you can combine fine-grained reusable predicates.

JSR 335, Project Lambda and lambdaj JSR 335 (Lambda Expressions for the Java Programming Language) is part of JSR 337 (Java SE 8), which is scheduled for release in late 2012. If you can not wait and need to start using that kind of syntax today, I recommend the lambdaj library, it is not the same but it is handy in some cases: Java Reflection (parte 1) - Blog - Arume. Clases de Utilidad Java VII: Reflection. Bueno, pues vamos a avanzar un poco más en nuestras clases de utilidad y hoy vamos a poner unos cuantos métodos con los que poder usar el API reflection.

Clases de Utilidad Java VII: Reflection

Éste API es muy usado dentro de la comunidad y es una herramienta muy potente a la hora de invocar métodos o clases por ejemplo definidos en base de datos. Obtener una clase a partir de un nombre: * Obtiene una clase a partir del nombre de la misma. * @param clazz La cadena que identifica la clase que se quiere obtener. * @return La clase correspondiente si se ha encontrado, y sino una excepción PLNException. Java concurrency (multi-threading) - tutorial. Java concurrency (multi-threading) - Tutorial Copyright © 2008-2015 vogella GmbH.

Java concurrency (multi-threading) - tutorial

Keytool

Guava. Upgrade from Tiles 2 to Tiles 3 on Spring MVC 3 application. I’ve just upgraded the web application that powers Podcastpedia.org to use Apache Tiles 3 instead of Tiles 2.

Upgrade from Tiles 2 to Tiles 3 on Spring MVC 3 application

I am particularly interested in the Tiles integration with Velocity for email generation. Note: You need at least the Spring 3.2 release for this to work. This occured in three small steps: upgrade maven dependenciesupgrade tiles elements in the Spring application contextupgrade tiles dtd version 1. What I had to do was just replace the ${tiles.version} in the maven pom.xml file from 2.2.2 to 3.0.1 for the Tiles dependencies I use, and now it looks like this: 2. The next thing was to upgrade to version 3 the tilesViewResolver and tilesConfigurer in the Spring application context: Tiles configuration in the Spring application context .................... <! Design Patterns in Java Tutorial. Design patterns represent the best practices used by experienced object-oriented software developers.

Design Patterns in Java Tutorial

Design patterns are solutions to general problems that software developers faced during software development. These solutions were obtained by trial and error by numerous software developers over quite a substantial period of time. This tutorial will take you through step by step approach and examples using Java while learning Design Pattern concepts. This reference has been prepared for the experienced developers to provide best solutions to certain problems faced during software development and for un-experienced developers to learn software design in an easy and faster way.

Before you start proceeding with this tutorial, I'm making an assumption that you are already aware about basic java programming concepts.

Struts 2

Play framework - Home. Java Weak Reference. Releasing unused objects for garbage collection can be done efficiently using java weak reference.

Java Weak Reference

Yes. weak reference is related to garbage collection. In java we need to not anything explicitly for garbage collection (GC), this memory management overhead is taken care by java run-time itself. Then what is the use of java weak reference? Let us see an example scenario, which will help us understand the problem in detail. Before that, we should be aware there are four types of references in java and they are strong reference, weak reference, soft reference and phantom reference. Weak Reference When there are one or more reference to an object it will not be garbage collected in Java.

Let us take a sample scenario to understand it better. Key is TextView object and value is the Id. So, programmatic we need to ensure that, when a textView is removed then its corresponding entry in the map should be removed. WeakHashMap. JBoss AS Storage Hints - jboss configuration.

EJBs

Retrieve Oracle version information. This Oracle tutorial explains how to find the Oracle version information with syntax and examples.

Retrieve Oracle version information

Description You can check the Oracle version by running a query from the command prompt. The version information is stored in a table called v$version. In this table you can find the version information for Oracle, PL/SQL, etc. Syntax The syntax to retrieve the Oracle version information is: SLF4J. Java - Using Jpcap to create JAVA applications that capture network traffic. Jpcap network packet capture library.

Network Packet Capture Facility for Java. Kaitoy/pcap4j. Programación con Java: 10 de las Mejores Prácticas en Java. 1.- Evitar la creación innecesaria de objetos, Lazy Initialitation La creación de objetos en Java es una de las operaciones mas costosas en términos de uso de memoria e impacto en el performance.

Programación con Java: 10 de las Mejores Prácticas en Java

Esto es evitable creando o inicializando objetos solo en el momento en que serán requeridos en el código. public class Paises { private List paises; public List getPaises() { //se inicializa solo cuando es requerido if(null == paises) { paises = new ArrayList(); } return paises; } } 2.- Nunca hacer variables de instancia públicas Hacer una clase publica se puede ocasionar problemas en un programa. Public class MiCalendario { public String[] diasDeLaSemana = {"Domingo", "Lunes", "Martes", "Miércoles", "Jueves", "Viernes", "Sábado"}; //mas código } La mejor práctica es como mucho de ustedes saben, es siempre definir estas variables como privadas y crear los métodos accesores, “setters“ y “getters” Pero escribir los métodos accesores no resuelve el problema del todo.

Buenas prácticas para la construcción de software. Your Source for Java Information.