Re: How to create an instance of type T?

From:
Daniel Pitts <newsgroup.spamfilter@virtualinfinity.net>
Newsgroups:
comp.lang.java.programmer
Date:
Sat, 23 Feb 2008 08:34:32 -0800
Message-ID:
<47c04b14$0$28586$7836cce5@newsrazor.net>
Joshua Cranmer wrote:

prowyh wrote:

I want to write a generic method that return the specified object
constructed with type parameter T and the parameter of type String.


Wherefore?

class GClass<T>
{
    public T getValue(String p) throws Exception
    {
        // create and instance of type T or a Class class of type T
        // construct the object with p by reflection
        // return the object
    }
}


You'll need to modify the code here somewhat:
class GClass<T> {
    private Class<T> clazz;

    public GClass<T>(Class<T> clazz) {
        this.clazz = clazz;
    }

    public T getValue(String p) throws Exception {
        return clazz.getConstructor(String.class).newInstance(p);
    }
}

Beware: reflection is slow.

Not *that* slow. Granted, slower than normal object instantiation, but
every Java release they seem to enhance the speed of reflection.

--
Daniel Pitts' Tech Blog: <http://virtualinfinity.net/wordpress/>

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