Details
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Improvement
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Status: Closed
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Major
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Resolution: Won't Fix
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None
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None
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None
Description
The "Closure" in commons collections is not named well: for non-functional programmers it will induce a "what's that?", and for functional programmers it will confuse expectations.
From http://en.wikipedia.org/wiki/Closure_(computer_science):
A closure combines the code of a function with a special lexical environment bound to that function (scope).
Java cannot pass functions, so the only way this can be done is with an (inner) class, as follows (also from wikipedia):
class CalculationWindow extends JFrame {
private JButton btnSave;
...
public final calculateInSeparateThread(final URI uri) {
// The expression "new Runnable()
" is an anonymous class.
Runnable runner = new Runnable() {
void run() {
// It can access final local variables:
calculate(uri);
// It can access private fields of the enclosing class:
btnSave.setEnabled(true);
}
};
new Thread(runner).start();
}
}
Note how the Runnable accesses the btnSave variable in the function scope. This "special lexical environment" is NOT the same as passing a parameter through a constructor OR execute method. A Closure should NOT take a parameter for execute. It is not actually possible to have a "Closure" object, as that breaks the lexical environment.
So, what to do?
I would propose an interface called Processor. It is more intuitive and has many "real world" examples that can anchor the term so that it makes sense to the average programmer.
For example, when applying for a passport, some documentation needs to be filled out, and then it will go through a process to get you a passport. You hand (or send) your forms to a clerk (Processor), and that's it. The Processor does not reply - the context that is passed in your form (your details) allows a message to be sent back at a later date.
For backwards compatibility the interface would be
public interface Processor<T> extends Closure<T>{}
with the appropriate documentation. Closure would be deprecated with an appropriate explanation.
However, it may be acceptable with the new version just to do a rename.