Simple Java type based on String

Question

I'd like a simple way of generating a type safe type based on String.

I have a bunch of places where I usually use just a String to hold opaque UID (example) and I'd like to move away from this.

java.lang.String is final. Ideally I would have liked to extend String but I understand I can't be doing that. What are my best options?

I know I can use an encapsulation but I am looking for something a bit more efficient, if at all possible.

Update: I want a meaningful name for the type i.e. not just UUID everywhere.

@Roddy: because I want to have a meaningful name for the type. — jldupont
– jldupont, Commented Sep 23, 2012 at 19:15
if i may ask, what would you name the type? mySuperSpecialUUID? i don't see the significance in wrapping a type just to give it a new name. — Alex Lynch
– Alex Lynch, Commented Sep 23, 2012 at 19:23
I just want to be as close as a String as possible without the overhead of another type... just to carry a String. — jldupont
– jldupont, Commented Sep 23, 2012 at 19:27

Ted Hopp · Accepted Answer · 2012-09-23 19:30:51Z

Because String is declared final, I think encapsulation is the only thing you can do. To provide some level of plug-compatibility, you can declare your class to implement CharSequence.

public class TypeSafeStringBase implements CharSequence {
    protected final String mString;
    protected TypeSafeStringBase(String string) {
        mString = string;
    }
    @Override
    public char charAt(int index) {
        return mString.charAt(index);
    }
    @Override
    public int length() {
        return mString.length();
    }
    @Override
    public CharSequence subSequence(int start, int end) {
        return mString.subSequence(start, end);
    }
    @Override
    public String toString() {
        return mString;
    }
}

public class ParamName extends TypeSafeStringBase {
    ParamName(String string) {
        super(string);
    }
}

public class Prompt extends TypeSafeStringBase {
    Prompt(String string) {
        super(string);
    }
}

// etc.

You might consider also declaring the base class to implement Serializable and Comparable<String> (or a type-safe Comparable for each subclass).

Alex Lynch · Accepted Answer · 2012-09-23 19:33:14Z

3

String inherits from CharSequence

If change your reference type CharSequence, you can use StringBuilder or any other mutable CharSequence.

Hope it helps.

edited Sep 23, 2012 at 19:33

Alex Lynch

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answered Sep 23, 2012 at 19:21

sharadendu sinha

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