Java J2EE Page

By Sidd Bhattacharjee
Java J2EE Page

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Difference between volatile and synchronized

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volatile is a field modifier, while synchronized modifies code blocks and methods. So we can specify three variations of a simple accessor using those two keywords: int i1; int geti1() {return i1;} volatile int i2; int geti2() {return i2;} int i3; synchronized int geti3() {return i3;} geti1() accesses the value currently stored in i1 in the current thread . Threads can have local copies of variables, and the data does not have to be the same as the data held in other threads. In particular, another thread may have updated i1 in it's thread, but the value in the current thread could be different from that updated value. In fact Java has the idea of a "main" memory, and this is the memory that holds the current "correct" value for variables. Threads can have their own copy of data for variables, and the thread copy can be different from the "main" memory. So in fact, it is possible for the "main...
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Converting Java Map to String

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Java Collections framework, String manipulation etc is something that we often encounter in Development process. For processing collections (like checking null/empty, Intersection, Disjunction) We do have some of the very use full libraries. Some of the Collection related libraries are Apche Commons Collections and Google  Collections(Guava). Problem Use Case This article explains how to convert a Java Map to String(and vice versa) using different libraries and technique. One way is to use StringBuilder(Or String) and loop though the Map and build the String by applying some sort of separator ( for key:value and entry). Here we have to take care of the null value etc. Without Any Library If we want to convert the map to a String with key value separator and also individual entry seperator in the resulting String, we have to write code for that. For a simple Map, we have to iterate though the map, take care of the null values etc. Following is...
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Builder Design Pattern

By Sidd Bhattacharjee
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Type : Creational Design Pattern Summary Builder pattern is a Creational Design Pattern and solves the problem of creating complex objects or objects whose constructor needs many parameters. Details Considering a Class whose constructor has a number of parameters, we have to send all of them to instantiate an instance, which could be error prone and complex sometimes. Also if the constructor has some optional parameters or if we want to have some parameters to have fixed value, we might end up with a number or Constructors for the object. Builder pattern solves this problem by exposing a builder object which can have multiple methods based on different parameters. Example For our example we will consider a Class BlogObject which represents a Blog and has a number of fields. Some of the fields like, Tag, Summary etc are optional. Without Builder we might need to have a number of constructors for the Class. But with Builder we can create the instance of the Object easily a...
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