I was reading some tutorials and documentation and came up with two different ways to declare RequestContext :
RequestContext requestContext = RequestContext.getCurrentInstance();
requestContext.execute(/*coisas*/);
and
RequestContext.getCurrentInstance().execute(/*coisas*/);
What I want to know is if there is any difference between these two, if so, which ones? When should I use each one?
In the first example, you are catching the instance of class RequestContext and inserting into a "local" variable ( RequestContext requestContext ) where its maintenance changes the state of the "Singleton" class (it seems) / p>
Now the second example ( RequestContext.getCurrentInstance().execute(/*coisas*/); ) would be taking the instance of the class itself and changing it, so if you need it in some local processing, doing RequestContext context = RequestContext.getCurrentInstance(); will already have the .execute() active.
Look at the codes:
Main.java class
private static Singleton singleton;
public static void main(String[] args) {
//Estou alterando a própria classe Singleton;
Singleton.getSingleton().setAtivo(false);
System.out.println(Singleton.getSingleton().isAtivo());//Imprime false
//Aqui a variável singleton está com a instância modificada da classe Singleton;
singleton = Singleton.getSingleton();
singleton.setAtivo(true);
System.out.println(singleton.isAtivo());//Imprime true
//O que acontece já que a variável singleton e a própria instância Singleton estão compartilhando informação;
Singleton.getSingleton().setAtivo(false);
System.out.println(singleton.isAtivo());//Imprime false
//Ou até:
singleton.setAtivo(true);
System.out.println(Singleton.getSingleton().isAtivo());//Imprime true
//Imprime true pois como a classe Singleton foi instanciada uma única vez (no próprio construtor da classe), as informações acabam compartilhadas;
}
Singleton.java class
private boolean ativo;
private static Singleton retorno = new Singleton();
private Singleton(){
this.setAtivo(false);
}
public static Singleton getSingleton(){
return retorno;
}
public boolean isAtivo() {
return ativo;
}
public void setAtivo(boolean ativo) {
this.ativo = ativo;
}
Note: I used the Singleton pattern because that was what the RequestContext class seemed to be.