Re: Interface with implied Constructor
In article <kri3sj$lnl$1@speranza.aioe.org>,
Richard Maher <maher_rjSPAMLESS@hotmail.com> wrote:
On 7/9/2013 7:08 PM, Robert Klemme wrote:
Why do you want to do that?
For me it's personal preference, but for some technical rationale: -
If you don't provide sufficient information to the constructor:
1) You get half-baked objects
2) Every real (non-init()) method now has to check "Has init() run? Am I
complete?"
3) If using setters, how do you enforce that they are called in the
correct order?
Most importantly, Why the hell do you think Java (and all other OO
languages) support arguments to constructors and overloading in the
first place??? Do you think the authors have been wasting their time or
providing redundant technology all these years?
So let me ask you "Why do you want to use setters or an init() method?"
Cheers Richard Maher
There's a builder pattern than works. It's a little ugly but it's what
you have when you can't use abstract classes for some reason. Move
around the interfaces as you see fit.
MyThingBuilder.java:
public interface MyThingBuilder
{
interface MyThing
{
String doThing ();
}
MyThing build(int arg1, String arg2);
}
MyThingBuilderImpl.java
public class MyThingBuilderImpl implements MyThingBuilder
{
@Override
public MyThing build(int arg1, String arg2)
{
return new MyThingImpl(arg1, arg2);
}
private static class MyThingImpl implements MyThingBuilder.MyThing
{
private final int arg1;
private final String arg2;
MyThingImpl (int arg1, String arg2)
{
this.arg1= arg1;
this.arg2= arg2;
}
@Override
public String doThing()
{
return "MyThingImpl(" + arg1 + ", " + arg2 +')';
}
}
}
Main code:
public static void main (String args[]) throws Exception
{
//From factory Class
final Class<? extends MyThingBuilder> c= MyThingBuilderImpl.class;
System.out.println(c.newInstance().build(1, "two").doThing());
//From Factory instance
final MyThingBuilder thing= new MyThingBuilderImpl();
System.out.println(thing.build(2, "three").doThing());
}
--
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