4

I am trying to do something like this:

public class Arquivo {

    private File diretorio  = null ;

    public Arquivo(File dir){
        this.diretorio = dir;
    }

    public Arquivo(String dir){
        this( new File(dir) );
    }

    public Arquivo(String fileName){
        this( new File("./src/Data/"+fileName) );
    }
}
jmj
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Hydrocat
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3 Answers3

10

You can't with constructor, that is one of the limitation of constructors

time to start using static factory pattern

See Also

Community
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jmj
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  • Also, consider how you would _use_ such a pair of constructors. What do you expect `new Arquivo("foo")` would do? Which constructor would it call? – yshavit Oct 28 '13 at 20:07
  • @ysha I could wrap the construction logic in conjunction with setters inside my factory method or I would use Builder pattern – jmj Oct 28 '13 at 20:08
  • Sorry, the "you" there was meant for the OP. :) I was getting at the fact that if Java did allow two constructors with the same signature, it would make usages of those constructors ambiguous. I +1'd your answer -- factory methods are the way to go here. – yshavit Oct 28 '13 at 20:09
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    Some more further reading: *[Effective Java](http://www.amazon.com/Effective-Java-Edition-Joshua-Bloch/dp/0321356683)*, Item 1, "[Consider static factory methods instead of constructors](http://my.safaribooksonline.com/book/programming/java/9780137150021/creating-and-destroying-objects/ch02lev1sec1)". – Jonik Oct 28 '13 at 20:19
3

You can't create two constructors that receive a single String parameter, there can only exist one such constructor. There must be a difference between the signatures, for example, add a second parameter to one of the constructors.

Alternatively, you could create a single constructor and indicate in a second parameter whether it's a file or a directory:

// isFile == true means it's a file. isFile == false means it's a directory
public Arquivo(String fileName, boolean isFile) {
    this(new File((isFile ? "./src/Data" : "") + fileName));
}
Óscar López
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-1

A constructor can not do that

a lazy solution would be

public Arquivo(String s) {}

public Arquivo(String s, boolean b) {}

and just don't use the boolean

mabdrabo
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  • is there a way to do something similar to this, however, using the the most resource-friendly path ?. the solution you provided may be more suitable for the occasion, otherwise, i would have to change some extra code in my project. – Hydrocat Oct 28 '13 at 21:02
  • It can be really, really confusing to use a 'magic boolean'. Coders not expecting this may waste time hunting down a boolean in the code that doesn't exist, and may presume one was deleted (by accident? Who knows?) without documentation. – AncientSwordRage Jan 03 '14 at 08:14
  • like you said `without documentation`, which is not right in its own. then i again i said `a lazy solution`, i agree with you however. – mabdrabo Jan 03 '14 at 11:28