System.out.println not responding ?

[achana chan]

Hi.
I've following piece of code which gets inserts a few records into an ArrayList and then try to display them with System.out.println on the Java console. However it is not displaying anything, no runtime errors either.
Maybe some can see some obvious flaw this time:

import java.util.*;
import java.io.*;
/**
 *  A TXRecord object encapsulates a transaction records
 */
public class TXRecord
{ // variables set at runtime by other applets...
  public int var_counter=0;
  public static TXRecord selfRef = null;
  private String acctName;
  List lst_acctName, lst_unitCost;
  //
  public void insertTXRecord(String var_acctName, String var_unitCost)
  {
    lst_acctName = new ArrayList();
    lst_unitCost = new ArrayList();
    // add runtime values to list elements...
    lst_acctName.add(var_acctName);
    lst_unitCost.add(var_unitCost);
    var_counter+=1;
    init();
  }
  public final String getTXRecord()
  { 
    return acctName;
  }
  public void init()
  {
    selfRef=this;
    for (int i=0; i<2; i++)
    {
      TXRecord txr = (TXRecord)(lst_acctName.get(i));
      System.out.println(txr.getTXRecord());
//      Iterator it_acctName = lst_acctName.iterator();
//        while(it_acctName.hasNext())
//        {System.out.println(String.valueOf(var_counter) + " " + it_acctName.next());}
//      Iterator it_unitCost = lst_acctName.iterator();
//        while(it_unitCost.hasNext())
//        {System.out.println(String.valueOf(var_counter) + " " + it_unitCost.next());}
    }
  }  
}

TIA :-)

[Dirk Schreckmann]

Your posted code doesn't include a runnable Java program - no main method.
As I see things, the only System.out.println occurs during the course of a for-loop in the init method. The init method is invoked from the insertTXRecord. But I don't see anything calling the insertTXRecord method.
If a main method is inserted, and the insertTXRecord method invoked, then the program throws a ClassCastException since a String that was inserted into an ArrayList is cast to a TXRecord. That's not allowed.
Also, are you sure you want to create two new ArrayLists and discard the old ones each time insertTXRecord is called?

[achana chan]

Its no good, Dirk, the moment I mod the code, Java console reports runtime NullPointerException. Even though insertTXRecord() method is called rather than TXRecord().

import java.util.*;
import java.io.*;
/**
 *  A TXRecord object encapsulates a transaction records
 */
public class TXRecord
{ // variables set at runtime by other applets...
  public int var_counter=0;
  public static TXRecord selfRef = null;
  private String acctName;
  List lst_acctName, lst_unitCost;
  //
  public TXRecord()
  { // created once only, by cbsMenu at startup...
    lst_acctName = new ArrayList();
    lst_unitCost = new ArrayList();
    init();
  }
  public void insertTXRecord(String var_acctName, String var_unitCost)
  {
    // add runtime values to list elements...
    lst_acctName.add(var_acctName);
    lst_unitCost.add(var_unitCost);
    var_counter+=1;
  }
  public final String getTXRecord()
  { 
    return acctName;
  }
  public void init()
  {
    selfRef=this;
    Iterator it_acctName = lst_acctName.iterator();
      while(it_acctName.hasNext())
      {System.out.println(String.valueOf(var_counter) + " " + it_acctName.next());}
    Iterator it_unitCost = lst_acctName.iterator();
      while(it_unitCost.hasNext())
      {System.out.println(String.valueOf(var_counter) + " " + it_unitCost.next());}
  }  
}

This is the startup applet that "loads" TXRecord *and* creates the ArrayLists for the first and only time for a given thread :

public class cbsMenu extends JApplet implements ActionListener, ItemListener
{
  TXRecord txrecord=null;
  // ...lots of related java...
  // ==============================
  public void TXRecord()
  { // creates the ArrayLists for holding transient TX records...
    txrecord = TXRecord.selfRef;
  }
  // ==============================
}// end of class ConfirmationFrame

And this is one of the applet which accesses the insertTXRecord(String, String) in TXRecord:

public class ConfirmationFrame extends JFrame               
{ // TCFrame for menu items action listener
  TXRecord txrecord = null;
  public ConfirmationFrame(URL codeBase, String baseInstr) throws IOException
  {  // ...unrelated Java
  /** Listens to the buttons and the combo box. */
  class prdDtlActionListener implements ActionListener
  {
    public void actionPerformed(ActionEvent aevt)
    { 
      if (aevt.getSource() == portfolioList) // action is on the combobox
      { portfolioName = (String)portfolioList.getSelectedItem();
      } else if (aevt.getSource() == back)   // back to product detail
      { 
        System.out.println("back button"); 
      } else if (aevt.getSource() == confirm)
      { var_acctName = "blank account name";
        var_unitCost = "blank unit cost";
        TXRecord();  // <---- DO I need this
        System.out.println("(1) ConfirmationFrame: "+ var_acctName + " : " + var_unitCost );
      } else if (aevt.getSource() == cancel) 
      { System.out.println("Cancelled");
        f.dispose();
      }
    }
  } // end of class prdDtlActionListener
  // ==============================
  public void TXRecord()
  { // get the static field where pointer to the instance of TXRecord is stored...
    txrecord = TXRecord.selfRef;
    // now you can call any methods in TXRecord...
    txrecord.insertTXRecord("yyyyy", "zzzzz");
  }

I'm sure at the end I'd kick myself, but at the moment I can't see the wood for the trees...
TIA :-)

[achana chan]

The above variation of my codes yield this disheartening Java console output

system datetime stamp: Feb 27, 2004 5:19:10 PM
java.lang.NullPointerException
at ConfirmationFrame.TXRecord(ConfirmationFrame.java:341)
...

[achana chan]

If I could any println to work, I'd be much further... :-(

[Mathews P Srampikal]

public void TXRecord() {
// get the static field where pointer to the instance of TXRecord is stored...
txrecord = TXRecord.selfRef;
// now you can call any methods in TXRecord... OK LETS SEE
System.out.println("Brfore");
txrecord.insertTXRecord("yyyyy", "zzzzz");
System.out.println("After");
}

Jus give 2 print stmt berfore and after below statement
txrecord.insertTXRecord("yyyyy", "zzzzz");
Is it printing After???

[achana chan]

Hi, Matthew.
Tried your suggestion

System.out.println("Before");
txrecord.insertTXRecord(var_acctName, var_unitCost);
System.out.println("After");

And following is the Java console output, so obviously something very bad happened in between...

system datetime stamp: Feb 27, 2004 11:40:00 PM
Before
java.lang.NullPointerException at ConfirmationFrame$prdDtlActionListener.actionPerformed(ConfirmationFrame.java:329)

[Stefan Wagner]

public final String getTXRecord()
{ 
        return acctName;
}
System.out.println(txr.getTXRecord());

As far as I can see, acctName is never set/ never assigned a value.
Therefor you get the NPE.