Arquivo do mês: janeiro 2009

Maravilha de Sun Spot!!!

Olhem isso:

Mais sobre Sun Spot aqui.

Sem dúvida, é o futuro!

João Sávio



Uma das chaves que leva ao sucesso:

João Sávio

Marketing Pessoal

Olá galera, vídeo bem explicativo sobre este tema:

João Sávio

Artigo sobre JSF

Aqui mais um artigo explicando um pouco sobre JSF (Java Server Faces).

João Sávio

Os 10 erros mais comuns em Java

Aqui encontra-se este artigo escrito por David Reilly.

João Sávio

Dicas SCJP

Direto do site da Kathy Sierra:

* Two top-level public classes cannot be in the same source file.
* main() cannot call an instance (non-static) method.
* Methods can have the same name as the constructor(s).
* Watch for thread initiation with classes that don’t have a run() method.
* Local classes cannot access non-final variables.
* Case statements must have values within permissible range.
* Watch for Math class being an option for immutable classes.
* instanceOf is not the same as instanceof.
* Constructors can be private.
* Assignment statements can be mistaken for a comparison; e.g., if(a=true)…
* Watch for System.exit() in try-catch-finally blocks.
* Watch for uninitialized variable references with no path of proper initialization.
* Order of try-catch-finally blocks matters.
* main() can be declared final.
* -0.0 == 0.0 is true.
* A class without abstract methods can still be declared abstract.
* RandomAccessFile descends from Object and implements DataInput and DataOutput.
* Map does not implement Collection.
* Dictionary is a class, not an interface.
* Collection (singular) is an Interface, but Collections (plural) is a helper class.
* Class declarations can come in any order (e.g., derived first, base next, etc.).
* Forward references to variables gives a compiler error.
* Multi-dimensional arrays can be “sparse” — i.e., if you imagine the array as a matrix, every row need not have the same number of columns.
* Arrays, whether local or class-level, are always initialized
* Strings are initialized to null, not empty string.
* An empty string is not the same as a null reference.
* A declaration cannot be labelled.
* continue must be in a loop (e.g., for, do, while). It cannot appear in case constructs.
* Primitive array types can never be assigned to each other, even though the primitives themselves can be assigned. For example, ArrayofLongPrimitives = ArrayofIntegerPrimitives gives compiler error even though longvar = intvar is perfectly valid.
* A constructor can throw any exception.
* Initializer blocks are executed in the order of declaration.
* Instance initializers are executed only if an object is constructed.
* All comparisons involving NaN and a non-NaN always result in false.
* Default type of a numeric literal with a decimal point is double.
* int and long operations / and % can throw an ArithmeticException, while float and double / and % never will (even in case of division by zero).
* == gives compiler error if the operands are cast-incompatible.
* You can never cast objects of sibling classes (sharing the same parent).
* equals() returns false if the object types are different. It does not raise a compiler error.
* No inner class can have a static member.
* File class has no methods to deal with the contents of the file.
* InputStream and OutputStream are abstract classes, while DataInput and DataOutput are interfaces.

Abraços e bons estudos!!!
João Sávio

Diferença SCJP 6 da SCJP 5

Segundo SCJP FAQ do site da Kathy Sierra:

How is the SCJP 1.6 exam different from the SCJP 1.5?

* Exam objectives: Several new API classes/interfaces have been added:, java.util.NavigableSet, java.util.NavigableMap. Explicit garbage collector calls (i.e. System.gc()) will no longer be tested, but candidates will still be expected to understand garbage collection and the finalize() method. Also, the following topics will be tested in greater depth: exception handling, collections, assertions, threads, and flow control. See the SCJP forum for more details.
* Number of questions: 72 (no change)
* Time: 210 minutes (increased from 175 minutes)
* Passing score: 65% (increased from 59%)
* Format of questions: No change.

João Sávio