Confusion with toString() method

hi...can you please tell me how to use the toString() method? i'm trying to print out a Vector and convert whatever is in it to strings but the memory addresses keep appearing. i tried using the method to convert (ie. getNames.toString, where getNames returns a vector, but it doesnt seem to work. i dont know what the problem is. i would really appreciate your help...

The objects in the Vector (or whatever collection
type you use) need to implement their owntoString()
method. Otherwise they just inherit
java.lang.Object's implementation, which gives you
the result you are seeing -- how should the system
magically know what to show for a string
representation of any willy-nilly object?Furthermore: the OP actually needs to call it on the
Vector's elements, not on the Vector itself.Not necessarily. I believe Vector.toString() iterates over the elements in it, invoking toString() on them.

Similar Messages

Having some problems with toString method.

Hi well my toString method is fine but what I don't understand is why am I getting the ouput for the toString where I am not supposed to.
import java.text.DecimalFormat;
    public class Sphere
   //Variable Declarations.
      private int diameter;
      private double radius;
   //Constructor: Accepts and initialize instance data.
       public Sphere(int sp_diameter)
         diameter = sp_diameter;
         radius =(double)diameter/2.0;
   //Set methods: Diameter
       public void setDiameter(int new_diameter)
         diameter = new_diameter;
         radius = (double) diameter/2.0;
   //Get methods: Diameter
       public int getDiameter()
         return diameter;
   //Compute volume and surface area of the sphere
       public double getVolume()
         return 4 * Math.PI * radius * radius * radius / 3;
       public double getArea()
         return 4 * Math.PI * radius * radius;
   //toString method will return one line description of the sphere
       public String toString()
         DecimalFormat fmt1=new DecimalFormat("0.###");
         String result = "Diameter : " + fmt1.format(diameter)+ "\tVolume: " + fmt1.format(getVolume()) + "\tArea: " +fmt1.format(getArea());
         return result; // This is fine .. the problem is the driver
Driver
       public static void main(String[]args)
         Sphere sphere1, sphere2, sphere3;
         sphere1 = new Sphere(10);
         sphere2 = new Sphere(12);
         sphere3 = new Sphere(20);
         System.out.println("The sphere diameter are: "); //Here is the problem for the output I only want the diameter, but I am getting the toString output here too..
         System.out.println("\tFirst Sphere diameter is: " + sphere1);
         System.out.println("\tSecond Sphere diameter is: "+ sphere2);
         System.out.println("\tThird Sphere diameter is: " + sphere3);
      //Prints the Sphere Volume and Surface Area.
         DecimalFormat fmt = new DecimalFormat("0.###");
         System.out.println("\nTheir Volume and Surface Area: ");
         System.out.println("\tSphere1: " + "Volume: " + fmt.format(sphere1.getVolume()) + "\tSurface Area: " + fmt.format(sphere1.getArea()));
         System.out.println("\tSphere2: " + "Volume: " + fmt.format(sphere2.getVolume()) + "\tSurface Area: " + fmt.format(sphere2.getArea()));
         System.out.println("\tSphere3: " + "Volume: " + fmt.format(sphere3.getVolume()) + "\tSurface Area: " + fmt.format(sphere3.getArea()));
      //Change the diameter of the sphere.
         sphere1.setDiameter(11);
         sphere2.setDiameter(15);
         sphere3.setDiameter(25);
         System.out.println("\nNew diameter is: ");
         System.out.println("\tFirst Sphere diameter is: " + sphere1);
         System.out.println("\tSecond Sphere diameter is: " + sphere2);
         System.out.println("\tThird Sphere diameter is: " + sphere3);
      //Prints the Sphere Volume and Surface Area.
         System.out.println("\nTheir Volume and Surface Area: ");
         System.out.println("\tSphere1: " + "Volume: " + fmt.format(sphere1.getVolume()) + "\t\tSurface Area: " + fmt.format(sphere1.getArea()));
         System.out.println("\tSphere2: " + "Volume: " + fmt.format(sphere2.getVolume()) + "\tSurface Area: " + fmt.format(sphere2.getArea()));
         System.out.println("\tSphere3: " + "Volume: " + fmt.format(sphere3.getVolume()) + "\tSurface Area: " + fmt.format(sphere3.getArea()));
      //Using the toString Method.
         System.out.println("\nFirst sphere: " + sphere1);
         System.out.println("\nSecond sphere: " + sphere2);
         System.out.println("\nThird sphere: " + sphere3);

System.out.println("The sphere diameter are: "); //Here is the problem for the output I only want the diameter, but I am getting the toString output here too..
System.out.println("\tFirst Sphere diameter is: " + sphere1);
System.out.println("\tSecond Sphere diameter is: "+ sphere2);
System.out.println("\tThird Sphere diameter is: " + sphere3);
If you only want the Diameter, than use a formatter and get the diameter like you did when you printed the surface area and volume. Or, print shpere1.getDiameter();
You have already demonstrated the solution to your problem elsewhere in your code, I think you need to re-read and understand what you have done so far.

Plz help.... toString() method

hi....i came accross this sample of toString method. I was wondering how do i return all the variables instead of dont concat ?Pleas help...
class ToStringClass {
String firstName;
String lastName;
public ToStringClass(String fname, String lname) {
this.firstName = fname;
this.lastName = lname;
// Override the toString() method
public String toString() {
return lastName + ", " + firstName;
}

sorry for the misleading question... here is the simple full coding of it
public class ToStringObjectExample {
    public static void main(String[] args) {
           // Overriding the equals() method
        ToStringClass tsc2 = new ToStringClass("Jane", "Doe");
        System.out.println("Class with toString() method    : " + tsc2);
class ToStringClass {
    String firstName;
    String lastName;
    public ToStringClass(String fname, String lname) {
        this.firstName = fname;
        this.lastName = lname;
    // Override the toString() method
    public String toString() {
        return lastName + ", " + firstName;
}the output will be display like :-
Class with toString() method    : Doe, JaneI was thinking how do i display or print the output directly like below :-
Doe
Jane
, which means that displaying the value of each variable. how do i do the return statement?

Confused with JList...

Ok... I'm working on a section of code for my GUI app that requires a JList (or something comparable).
I've read the tutorials and API, and I'm getting confused on how to do what I want. From what I gather, I need to use a ListModel and a listener, but putting it all together is the problem.
Here is what I am trying to accomplish:
I'm writing an RMI group chat app. It's came together wonderfully so far (I just have GUI issues and a couple features to add). I need a user list with the users currently online. Since the users online with vary often, the list needs to be changed dynamically. There's more... The users are divided by department, and the department has a colored heading in the list, the users for that department are underneath it.
Here's how I am handling the data:
When a user joins or exits, the server fires a remote call to each client to update the userlist. It passes the departments and users as a hashtable. I then loop through each department (setting the department to the list with a colored cell). While each department is looped through, it loops through the users hash to see if they are in that department. If they are, it adds that username to the list. Obviously, since the list will be updated continuouly, the list must be cleared before it is repopulated. Finally, when any user is clicked on, it invokes a method (the method is arbituary at this point).
I know this is a lot of code, but I'm confused on how to even begin this section of my app. If anyone has a solution or can point me in the right direction, that would wonderful.
Thanks so much!
Jason

Well, you could just clear all and loop thru and create a Vector or Object[] and call setListData() on the list, which will update. However, this is not the best approach because of all the processing of the list for each change.
What I would do is first create a class extending AbstractListModel which can hold all your list items. So you need an add method and remove method, and a list to store the objects in, like ArrayList. If possible, just add or remove whatever was actually added or removed, don't update the whole list. The getElementAt method can just call the get method on the internal list.
Then create an object that implements comparable that contains the user name and the department they are in. The compareTo method can check the departments and if they are equal, compare the names to sort, otherwise compare the department strings. This will allow the objects to be sorted in the list easily. Make sure to implement equals in the object as well.
For add, after adding to the internal list, sort it with Collection.sort(), find the index of the item just added and call fireIntervalAdded(this, index, index) from the AbstractListModel. For remove, get the current index, then remove the item and call fireIntervalRemoved(this, index, index). The fire... methods will tell the JList itself to repaint.
The object to store the value might need more info in it then user and dept name, like color to use. And you could then create a cell renderer to enable drawing of the items, otherwise it'll use the toString method to get the string to show.
Registering a listener, the listener will get the actual object from your internal list as the selected item, so based on that you can do whatever.

I'm confused about accessor methods.

Part of the application I'm developing translates a sequence of strings into a series of hex values. The number of strings will be either 2 or 3. In the cass where there's 3 strings the last would represent an integer or a decimal fraction.
I have a class Xlate that has 3 translation methods thus:
public int[] translate(String msg) {};
public int[] translate(String msg, int val) {};
public int[] translate(String msg, String aValString) {};
The problem I have is that the Xlate does not return what is expected when passed an argument via the method signature. If explicitly passed a string sequence it works OK.
If I pass the argumants... "pause" "21.09876"
I would expect to see a translation of ... "msg translation array = 76,98,10,20,0A"
What I get is "msg translation array = FF, FF, FF, FF,FF" which indicates the array has not been amended after initialised.
This is most likely due to the lack of accessor definitions and their use. HOWEVER, I am confused by such methods.
I now realise that to pass values setter/getter accessor methods are .
I think these might be along the lines of the following:
private String[] commandList; // declares a string variable
public Xlate() { this(""); }
public Xlate(String[] msg) { this.commandList = msg[1]; } // holds the name
public String getCommandStrings() { return this.commandList; } // gets the commandList
I can't get this to work and know these are not correct.
I need help to get me moving ahead of this problem. Any help would be appreciated.
Thanks.
Philip
import java.lang.String;
public class Control {
public Control() {
   int i;
static final public Xlate x = new Xlate();
// static final public Comms rc = new Comms();
public static void main(String[] args) {
    String cmd[] = args;
    for (int i=0;i<args.length;i++)
      cmd=args[i];
controller(cmd);
// public static void controller(String portName, String command, String parameter) {
public static void controller(String[] parameters) {
Control c = new Control();
int[] msg ={1,1,1,1,1};
// Booleans 'pragmaN' are used to select/deselect debug statements
// though would be embedded in the bytecode
// so these are not compiler directives
boolean pragma1=true, pragma2=true, pragma3=true; // toggle using !
int pVal;
if (pragma1==true) {
System.out.print("msg array = ");
for (pVal=0; pVal<4;pVal++)
     System.out.print(Integer.toHexString(msg[pVal]).toUpperCase() + ",");
System.out.println(Integer.toHexString(msg[pVal++]).toUpperCase());
// rc.setupComPort(parameters[0]); // Configure the port referenced
msg = x.translate("start"); //*********TRANSLATE()************
msg = x.translate("pause","12.34567"); //*********TRANSLATE()************
if (pragma2==true) {
System.out.print("msg translation array = ");
for (pVal=0; pVal<4;pVal++)
     System.out.print(Integer.toHexString(msg[pVal]).toUpperCase() + ",");
System.out.println(Integer.toHexString(msg[pVal++]).toUpperCase());
// rc.writeCmd(msg);
// Control messages have 3 fixed formats comprising 'a string', 'a string
// plus an integer' and 'a String plus a String'.
// For the control messages with an argument a string is constructed before
// translation by parging the arguments.
// Do ensure the number of args is greater than 1 and less than 3.
// Converts integer types to Strings
String argString="";
System.out.println("arg len = "+ parameters.length);;
switch (parameters.length) {
case 2:
     System.out.println("in switch 2");;
     argString = (parameters[1]);
     msg = x.translate(argString); //*********TRANSLATE()************
     if (pragma3==true) {
     System.out.print("msg translation array = ");
     for (pVal=0; pVal<4;pVal++)
     System.out.print(Integer.toHexString(msg[pVal]).toUpperCase() + ",");
     System.out.println(Integer.toHexString(msg[pVal++]).toUpperCase());
     break;
case 3:
     if (pragma3==true) {
     System.out.println("in switch 3"); ;
     argString = (parameters[1] + parameters[2]);
     msg = x.translate(argString); //*********TRANSLATE()************
     if (pragma3==true) {
     System.out.print("msg translation array = ");
     for (pVal=0; pVal<4;pVal++)
     System.out.print(Integer.toHexString(msg[pVal]).toUpperCase() + ",");
     System.out.println(Integer.toHexString(msg[pVal++]).toUpperCase());
     break;
default:
     System.out.println("Argument length error");
break;
// rc.writeCmd(msg);
import java.text.*;
import java.text.StringCharacterIterator; // required for CharacterIterator class
public class Xlate {
private String[] commandList; // declares a string variable
public Xlate() { this(""); }
public Xlate(String[] msg) { this.commandList = msg[1]; } // holds the name
public String getCommandStrings() { return this.commandList; } // gets the commandList
// These methods form a basic translation mechanism used as proof
public int[] translate(String msg) {
int[] paramList = {
     0xFF, 0xFF, 0xFF, 0xFF, 0xFF}; //initialise this array
//Power On and Off controls
if (msg == "start") {
paramList = new int[] {
     0xFF, 0xFF, 0xFF, 0x01, 0x20};
if (msg == "stop") {
paramList = new int[] {
     0xFF, 0xFF, 0xFF, 0x00, 0x20};
return (paramList);
public int[] translate(String msg, int val) {
int[] paramList = {};
int pVal;
// Memory recall with memory ID.
if (msg == "M") { // Recall memory
paramList = new int[] {
     0xFF, 0xFF, 0xFF, 0xFF, 0x02};
// stuff the argument in to the paramList array
paramList[3] = Integer.decode(Integer.toHexString(val)).shortValue();
return (paramList);
public int[] translate(String msg, String aValString) {
// Convert the string
    int i, j, k;
    int index = 0, c = 0;
    int[] p, paramList = {};
    final StringBuffer result = new StringBuffer(); // only ever one buffer
    char character;
    if (msg == "pause") {
      paramList = new int[] {
       0xFF, 0xFF, 0xFF, 0xFF, 0x0A};
// The period character is the axle where operations centre...
// working from the left most position index until period is found.
// append chars to result string en route.
// if period then stop - this is the integer part
    StringCharacterIterator sci = new StringCharacterIterator(aValString);
    result.append('0'); // a fudge to pad out the resulting string
    character = sci.current();
    while (character != '.') {
      //char is not a period so append to buffer
      result.append(character);
      character = sci.next();
    character = sci.next();
// working from the position of 'the period character' append chars to result string en route.
// stop at the end having bound the fraction part
    while (character != StringCharacterIterator.DONE) {
      result.append(character);
      character = sci.next();
    aValString = result.toString(); // save the result
    sci = new StringCharacterIterator(aValString);
    String[] part = {
     "00", "00", "00", "00"}; // array index ordered 0 to 3 from left to right
    result.delete(0, result.capacity()); // initialise the StringBuffer result
    character = sci.first();
    for (index = 0; index <= 3; ++index) {
      for (i = 0; i <= 1; ++i) {
     if (character != StringCharacterIterator.DONE) {
       result.append(character);
       character = sci.next();
     else {
       result.append('0');
      part[index] = result.toString();
      result.delete(0, result.capacity()); // initialise the StringBuffer result
// the sequence handles the conversion of decimal to packed BCD for transmission
    for (k = 0; k <= 3; k++) {
      // cast the String in the array part indexed by k to an int
      i = Integer.parseInt(part[k]);
      for (j = 0; j < 10; j++) {
     if ( (i >= (j * 10)) & (i < ( (j + 1) * 10))) {
       paramList[k] = (j * 0x10 + (i - (j * 10)));
    return (paramList);

Sorry, this is way too much to look at (at least for me). Please create a small test function that fails & post the formatted code. In doing this, you may even spot the problem yourself!

Using JOptionPane to exit program & Using toString method

Hello,
In my program I have to use a toString method below
public String toString(Hw1NCBEmployee[] e)
        String returnMe = String.format(getStoreName() + "\n" + getStoreAddress() + "\n" + getCityState() + "\nYou have " + getEmpCount() + "employee(s)");
        return returnMe;
}Now, at first, when I initially tested my code, it was working just fine, printing out the right way
Point is -- now that Im practically finished with my program, and am going back and running it - calling the toString method gives me the address rather than the information . . . Can anyone help me with this issue??
Also, Im using JOptionPane to display everything, but -- at first, it worked fine, then (around the same time I started having the above problem) it stopped exiting the do-while loop:
while(go)
             int option = JOptionPane.showConfirmDialog(null, "Do you want to enter employee information?", "Welcome!", JOptionPane.YES_NO_OPTION);
                 if(option == JOptionPane.NO_OPTION)
                    go = false; //exit loop


ncjb wrote:
well, for the toString - I have to print out the info inside the array -- am I right in thinking that the only way to do this is to pass in the array ??If the array is part of the class then there is no need to pass it as a parameter. If it is being passed in from outside the class then I have to question your design. Why should class X being formatting data that is not a representation of itself?
and i have 2 other files that go with this program . . . I just want to know if there is a way to make sure that when the user presses the NO option, it will exit the loop -- the piece of code you see if apart of an entire method (not long) -- do you want me to include this??You read that link I provided REAL quick!

Socket Programing in J2ME - Confused with Sun Sample Code

Hai Everybody,
I have confused with sample code provided by Sun Inc , for the demo of socket programming in J2ME. I found the code in the API specification of J2ME. The code look like :-
// Create the server listening socket for port 1234
ServerSocketConnection scn =(ServerSocketConnection) Connector.open("socket://:1234");
where Connector.open() method return an interface Connection which is the base interface of ServerSocketConnection. I have confused with this line , is it is possible to cast base class object to the derived class object?
Plese help me in this regards
Thanks in advance
Sulfikkar

There is nothing to be confused about. The Connector factory creates an implementation of one of the extentions of the Connection interface and returns it.
For a serversocket "socket://<port>" it will return an implementation of the ServerSocketConnection interface. You don't need to know what the implementation looks like. You'll only need to cast the Connection to a ServerSocketConnection .

JSP Tags, EL and toString() method

Hi,
I want to pass a Java object to a custom tag via EL, but am finding that since the class has a toString() method, EL automatically converts the class to a string using the toString method. Consequently, I get an error because the string cannot be cast back to the parent object in the tag handler class.
I played around with a dummy class and found that if the toString() method wasn't defined, EL would pass the object as is without converting to a string.
Is there some reason for this behaviour and is there some way I can get around this without having to remove the toString() method ? The object I am trying to process is from an external library, so I can't modify it.
Thanks for any tips on this.
Paul Samuel

My initial guess was that you hadn't defined the type of the attribute, and it was defaulting to String as a result. Now that I've seen the tld file thats obviously not the cause.
Next guess: EL evaluation is disabled, and it is interpreting ${model.results} as a string, rather than evaluating it.
1 - What happens if you just put ${1 + 1} onto a JSP page. Does it print ${1 + 1} or evaluate it as 2?
2 - What server are you using? What version? Which J2EE spec does it support?
You can use the following JSP snippet to confirm this info:
<h2> Server Info</h2>
Server info = <%= application.getServerInfo() %> <br>
Servlet engine version = <%= application.getMajorVersion() %>.<%= application.getMinorVersion() %><br>
Java version = <%= System.getProperty("java.vm.version") %><br>
Session id = <%= session.getId() %><br>3 - What version is your web.xml declared as? 2.3 or 2.4?
4- If you have a Servlet2.4/JSP2.0 container (eg Tomcat 5), try putting the following on your page and see if it works
<%@ page isELIgnored="false" %>
http://forum.java.sun.com/thread.jspa?threadID=629437&tstart=0
Cheers,
evnafets

Problem Using toString method from a different class

Hi,
I can not get the toString method to work from another class.
// First Class Separate file MyClass1.java
public class MyClass1 {
     private long num1;
     private double num2;
   public MyClass1 (long num1, double num2) throws OneException, AnotherException {
        // Some Code Here...
    // Override the toString() method
   public String toString() {
        return "Number 1: " + num1+ " Number 2:" + num2 + ".";
// Second Class Separate file MyClass2.java
public class MyClass2 {
    public static void main(String[] args) {
        try {
           MyClass1 myobject = new MyClass1(3456789, 150000);
           System.out.println(myobject);
         } catch (OneException e) {
              System.out.println(e.getMessage());
         } catch (AnotherException e) {
              System.out.println(e.getMessage());
}My problem is with the System.out.println(myobject);
If I leave it this way it displays. Number 1: 0 Number 2: 0
If I change the toSting method to accept the parameters like so..
public String toString(long num1, double num2) {
      return "Number 1: " + num1 + " Number 2:" + num2 + ".";
   }Then the program will print out the name of the class with some garbage after it MyClass1@fabe9. What am I doing wrong?
The desired output is:
"Number 1: 3456789 Number 2: 150000."
Thanks a lot in advance for any advice.

Well here is the entire code. All that MyClass1 did was check the numbers and then throw an error if one was too high or too low.
// First Class Separate file MyClass1.java public class MyClass1 {
     private long num1;
     private double num2;
     public MyClass1 (long num1, double num2) throws OneException, AnotherException {
     // Check num2 to see if it is greater than 200,000
     if (num2 < 10000) {
            throw new OneException("ERROR!: " +num2 + " is too low!");
     // Check num2 to see if it is greater than 200,000
     if (num2 > 200000) {
            throw new AnotherException ("ERROR!: " +num2 + " is too high!");
     // Override the toString() method
     public String toString() {
          return "Number 1: " + num1+ " Number 2:" + num2 + ".";
// Second Class Separate file MyClass2.java
public class MyClass2 {
    // Main method where the program begins.
    public static void main(String[] args) {
        // Instantiate first MyClass object.
        try {
           MyClass1 myobject = new MyClass1 (3456789, 150000);
           // if successful use MyClass1 toString() method.
           System.out.println(myobject);
                     // Catch the exceptions within the main method and print appropriate
                     // error messages.
         } catch (OneException e) {
              System.out.println(e.getMessage());
         } catch (AnotherException e) {
              System.out.println(e.getMessage());
         }I am not sure what is buggy. Everything else is working fine.

Overriding toString() method

hello all,
in the following class how toString() is overriding?
class Box {
    public Box(){
    public String toString(){
        return "Hello";
    public static void main(String args[]){
        System.out.println(new Box());
}even though i am not extending anything.
how the toString() method of String class is overriding here?
is it due to Object class?
thanks
daya

even though i am not extending anything.
how the toString() method of String class is
overriding here?
is it due to Object class?Yes, thats it exactly. Even when you do not extend and class, by default every class inherits from the Object class. Since toString is defined in the Object class, you override it when you defing toString with the same signature.

Using a toString() method to round decimals

I've been working on this project for school, building a class which models cartesian coordinates and can also convert them to polar coordinates. After much work I have a working product with some time to spare. Theres a small amount of extra credit to be gained if i can use toString() methods to manipulate my results to be exactly to two decimal places.
I've been looking at the api documentation, which is what my teacher suggested, but its a little tough for a rookie like me to wade through. A point in the right direction or any help would be greatly apreciated.
Thanks in advance

I understand, I just dont want yall to feel like youre doing all the work for me.
Anyways i searched google and using what i saw on this site
http://www.particle.kth.se/~lindsey/JavaCourse/Book/Part1/Tech/Chapter05/decimalFormat.html
adapted what i could to my class and came up with this
String fmt = "0.00";
DecimalFormat df = new DecimalFormat( fmt );
String str_x = df.format(x);
String str_y = df.format(y);
public String toString()
return "( " + str_x + ", " + str_y + " )";
}x and y are the instance variables im using for my class: Coord
when i try to compile i get these two error messages:
Coord.java:133: cannot find symbol
symbol : class DecimalFormat
location: class Coord
DecimalFormat df = new DecimalFormat( fmt );
^
Coord.java:133: cannot find symbol
symbol : class DecimalFormat
location: class Coord
DecimalFormat df = new DecimalFormat( fmt );
^
I assume these errors mean my syntax is off but hopefully im headed in the right direction.

Overiding the toString method

If I have a method which takes an array of strings as the first argument and a string as the second argument.
I will compare the string to each index in the passed in array and add the smaller strings to an arraylist.
firstly to return an ArrayList, what type of method would it be, String?
Then how is the toString method overridden to print out the ArrayList if the ArrayList could vary depending on the passed in arguments?
;)

Encephalopathic wrote:
Implode wrote:
If I want to print out an ArrayList using a for loop, the toString method needs to be overridden?No, not at all. You simply loop through the ArrayList and println each element. Now if the elements are complex objects, then the toString method of the class that the elements are composed of may need a toString override.
I had to do that with previous examples.Code is worth a thousand words. What do you mean here? Did what?
Yeah, sorry, I guess I never explained properly. I know how to override toString method, (totally serperate question)but what if the ArrayList was containing object references , and the ArrayList was built depending on arguments passed to a method , how would the toString be overridden then?Again, you would need to have a toString override of the objects held by the ArrayList, not the ArrayList itself.
For e.g.,
import java.util.ArrayList;
import java.util.Random;
public class MyFoo {
private String text;
private int value;
public MyFoo(String text, int value) {
super();
this.text = text;
this.value = value;
@Override // here's the necessary toString override
public String toString() {
return text + ": " + value;
public static void main(String[] args) {
String[] strings = {"Mon", "Tues", "Wed", "Thurs", "Fri"};
Random random = new Random();
ArrayList<MyFoo> fooList = new ArrayList<MyFoo>();
for (String text : strings) {
fooList.add(new MyFoo(text, random.nextInt(100)));
// to print out in a for loop:
for (MyFoo myFoo : fooList) {
System.out.println(myFoo);
}Edited by: Encephalopathic on Nov 15, 2009 9:11 AMI did override toString using complex objects in previous examples(university assignments).
Thanks for the help. Forget the question. It was sidetrack.
Edited by: Implode on Nov 15, 2009 9:23 AM

Polymorphism with Overloaded Methods

I am running into a problem when I try to leverage java��s polymorphism with overloaded Methods. Basically, what I am trying to do is iterate through a generic list of properties and call the correct overloaded method on each one based on the type of containing object.
Here is the general code (4 classes)
AbstractCronJob �� EmailCronJob
BaseProperty �� SubjectLineProperty
public abstract class BaseProperty implements CronPropertyExecutable{
    public BaseProperty() {
        super();
   public void execute(AbstractCronJob job) {
       System.out.println( "executing on abstract cron job" ) ;
public class SubjectLineProperty extends BaseProperty {
    public SubjectLineProperty() {
        super();
    public final void execute( EmailCronJob emailCronJob ) {
        System.out.println( "executing on email cron job" ) ;
public abstract class AbstractCronJob {
    protected int _id ;
    protected PropertyList _propertyList ;
    public AbstractCronJob( int id ) {
        super();
        _id = id ;
        _propertyList = new PropertyList() ;
    protected void createProperties() {
        //fill in with factory crap
        _propertyList.add( new SubjectLineProperty() ) ;
    protected abstract void executeProperties();
    protected abstract void run() ;
    public void execute() {
        createProperties() ;
        executeProperties() ;
        run() ;
public class EmailCronJob extends AbstractCronJob {
    public EmailCronJob( int id ) {
        super( id ) ;
    /* (non-Javadoc)
     * @see com.reged.cron.AbstractCronJob#run()
    protected void run() {
        //send email
    protected void executeProperties() {
        //we had this as abstract...unless I'm missing something, we can do this
        //in this class instead of pushing it down
        Iterator iter = _propertyList.iterator() ;
        while ( iter.hasNext() ) {
            //safe cast
            BaseProperty baseProperty = ( BaseProperty ) iter.next() ;
            baseProperty.execute( this ) ;
}Okay, here is the problem that I am running into. The EmailCronJob knows that it has a list of properties, it doesn't know what type of properties it as. So when it iterates through its property list it upcasts then to the BaseProperty parent class. Then it calls the execute method on each property passing in itself.
I thought that the execute(EmailCronJob job) method in SubjectLineProperty would be executed since the overloaded method with the mailCronJob parameter lives in that class, instead I am finding that the execute(AbstractCronJob job) method in the BaseProperty class is eing exercised.
I am confused on why this doesn't work. Does polymorphism work with overloaded methods or just overridden methods?
Thanks!

We can think about it based on suppositions, satisfactory explanations, and based on OO design.
According to the experience from the code above, we can suppose that, at runtime, the virtual machine looks for an exact identical signature of an method to perform the overriding.
But, why does it work in that way? Is there any good justification, or is it just a implementation decision?
I think there is a good justification.
Let me get the Object.equals() method as an example, and let�s make an analogy with the code above. According to our conclusions from the experience above, that we suppose are right and should work, but actually they should not work, in order to use the equals() method, we can simply do this:
class TheClass {
private int whatever;
public TheClass(int param) {
    whatever = param;
//notice that the param is not Object
public boolean equals(TheClass param) {
    //we don�t need either to cast to TheClass or
    //verify if the param is an instance of TheClass
    if (this == param) return false;
    if (this.whatever == param.whatever) return true;
    else return false;
}Apparently, this equals() method above is more efficient, and it does make sense, too, and it would be considered a good and logic implementation of equals() method. Although, these conclusions are wrong, if you consider some OO concepts that are being broken here.
equals() method is defined in Object class as an contract, like an interface. It says that this method must receive an Object param. And according to this contract, two instances of Object can use this method. You have to obey this contract, because it is Oriented Object Programming.
If you use equals method without passing Object as an parameter, but passing other different class (like TheClass, in my example), you would not obey the contract, that says that two instances of Object can use this method. Try to do this:
public static void main(String[] args) {
    TheClass theClass1 = new TheClass(1);
    TheClass theClass2 = new TheClass(1);
    //Good, more or less, because our objective, that is,
    //calling the customized equals(), will be performed.
    System.out.println(theClass1.equals(theClass2));
    String str = "blah";
    //oops! The customized equals() method will not
    //be called this time
    System.out.println(theClass1.equals(str));
    Object obj1 = theClass1;
    Object obj2 = theClass2;
    //Again, the customized equals() method will not
    //be called this time. Thanks God it works in this way!
    //Because if the customized equals() method
    //could be called here, the "OO law"
    //and the "contract" of equals method
    //defined in Object class would be broken
    System.out.println(obj1.equals(obj2));
}Therefore, I think Java working in this way is good, because it obligates us to "obey the laws", in certain way.

Confusion with Image/BufferedImage

Hello,
I'm trying to write an applet that displays and modifies local image files (gif). I'm running into some confusion with the different image APIs and drawing methods though.
I want to read the files, display them, and then create new images from sections of the original ones. I wrote an applet that succesfully loads and displays files as Image objects, but then I saw that BufferedImage has a method getSubImage() that I thought I could use to create the new images.
But my problem is that even without manipulating the images, I can't get them to display as BufferedImages. Here's the code, where I try to display the series of images twice, once as Image, once as BufferedImage, but the BI come out as black squares.
public class myapplet extends Applet
     BufferedImage[] img = new BufferedImage[NUM_PICS];
     Image[] im = new Image[NUM_PICS];
     public void init()
          Toolkit t = Toolkit.getDefaultToolkit();
          Graphics2D bg;
          MediaTracker tracker = new MediaTracker (this);
          for(int i = 0;i<NUM_PICS;i++)
               try
                    im[i] = t.getImage(gen.getLogo());
//the getLogo method is from a class I wrote -
//it returns a string with a filename
               catch(Exception e)
                    System.out.println("ERROR: "+e.getMessage());
               img[i] = new BufferedImage(70, 70,BufferedImage.TYPE_INT_RGB);
bg = img[i].createGraphics();
bg.drawImage(im[i],0,0,this);
     public void paint(Graphics g)
          Graphics2D g2 = (Graphics2D)g;
          for(int i=0;i<NUM_PICS;i++)
               g.drawImage(im[i],10,i*70,this);
               g2.drawImage(img[i],null,80,i*70);
Any help would be great.

You have to use the MediaTracker before drawing the image onto the BufferedImage:
try {
im[i] = t.getImage(gen.getLogo());
tracker.addImage(im[i], i);
tracker.waitForID(i);

RE: (forte-users) Confusion with return event

Samer,
The return event is delivered to the calling task, which is the window in
your first test. It is not deliverd to the event loop of the service object
unless the call to the processor originated in the event loop, which is the
case in your second test. The output you get from the server is exactly as I
would expect.
You need the following code in you client:
event loop
postregister
SomeService1.StartImmediate();
when SomeService1.Proc.ProcessEvent_return do
task.Part.Logmgr.Putline('ProcessEvents_return');
when SomeService1.Proc.ProcessEvent_exception do
task.Part.Logmgr.Putline('ProcessEvents_exception');
end event;
Note that this logoutput will not be written to a logfile, but will appear
in the logwindow which is opened when you start a client application.
Pascal Rottier
Atos Origin Nederland (BAS/West End User Computing)
Tel. +31 (0)10-2661223
Fax. +31 (0)10-2661199
E-mail: Pascal.Rottiernl.origin-it.com
++++++++++++++++++++++++++++
Philip Morris (Afd. MIS)
Tel. +31 (0)164-295149
Fax. +31 (0)164-294444
E-mail: Rottier.Pascalpmintl.ch
-----Original Message-----
From: Samer Kanjo [mailto:skanjoyahoo.com]
Sent: Thursday, January 18, 2001 1:54 AM
To: ForteUsers
Subject: (forte-users) Confusion with return event
I have observed some odd behavior when attempting to
catch a return event for a method invoked using start
task. I provided the primary classes I used during my
test and some output produced by those classes at the
bottom of this message.
The SomeService1 class is used to create an
environment visible service object and the Processor
class is one of its members. The Processor class
starts processing when one of two things happens: the
SomeService1 timer ticks off 10 seconds or when
SomeService1.StartImmediate is called directly by
another entity. Either way StartImmediate is called to
start processing.
The provided output is the result of starting a test
application and invoking StartImmediate from another
object (I used a window) and then observing what
happens when the timer ticks. As you can see the
invocation from the window did not result in the
return event being received. However, the return event
was received when the timer ticked.
According to the Forte documentation a return event
will only be posted to the parent task's event queue.
Since I am making a cross partition call, the window
and service object are not really in the same task
(Unless my assumption is wrong). That would explain
why the window did not cause a return event to be
generated but was an event generated but not caught
and if so where did the event go?
In SomeService2 class I added an event StartProcessing
and moved the code from StartImmediate to the
StartProcessing event case in the event loop and
simply posted the StartProcessing event in
StartImmediate. I performed the same test I used when
testing SomeService1. The Traceback output is
identical for the window invocation but the return
event is received this time! Why?
It seems that to guarantee the receipt of a return
event an asynchronous task must be initiated from
within an event loop. Is this correct?
I do not understand this behavior does someone have
any thoughts on this? How can you guarantee the
receipt of a return event?
Samer Kanjo
OUTPUT FROM SOMESERVICE1
StartTaskTest_cl0: processing loop listening
StartTaskTest_cl0:
Traceback:
SomeService.StartImmediate at line 1
TestWin.Display at line 4
C++ Method(s)
UserApp.Run at offset 105
StartTaskTest_cl0:
StartTaskTest_cl0: Start processing...
StartTaskTest_cl0: Processing complete.
StartTaskTest_cl0:
Traceback:
SomeService.StartImmediate at line 1
SomeService.ProcessingLoop at line 9
StartTaskTest_cl0:
StartTaskTest_cl0: Start processing...
StartTaskTest_cl0: Processing complete.
StartTaskTest_cl0: ProcessEvents_return
OUTPUT FROM SOMESERVICE2
StartTaskTest_cl0: processing loop listening
StartTaskTest_cl0:
Traceback:
SomeService2.StartImmediate at line 1
TestWin.Display at line 4
C++ Method(s)
UserApp.Run at offset 105
StartTaskTest_cl0:
StartTaskTest_cl0: Start processing...
StartTaskTest_cl0: Processing complete.
StartTaskTest_cl0: ProcessEvents_return
StartTaskTest_cl0:
Traceback:
SomeService2.StartImmediate at line 1
SomeService2.ProcessingLoop at line 9
StartTaskTest_cl0:
StartTaskTest_cl0: Start processing...
StartTaskTest_cl0: Processing complete.
StartTaskTest_cl0: ProcessEvents_return
SOMESERVICE1 CLASS
begin CLASS;
class SomeService1 inherits from Framework.Object
has public attribute proc: StartTaskTest.Processor;
has public attribute processing: Framework.boolean;
has public method Init;
has public method ProcessingLoop;
has public method StartImmediate;
has property
shared=(allow=off, override=on);
transactional=(allow=off, override=on);
monitored=(allow=off, override=on);
distributed=(allow=on, override=on, default=off);
end class;
method SomeService1.Init
begin
super.Init();
processing = FALSE;
proc = new;
start task ProcessingLoop();
end method;
method SomeService1.ProcessingLoop
begin
timer : Timer = new;
timer.tickInterval = 10000;
event loop
task.part.logmgr.putline('processing loop
listening');
timer.isActive = TRUE;
when timer.tick do
StartImmediate();
when proc.ProcessEvents_return do
task.part.logmgr.putline('ProcessEvents_return');
processing = FALSE;
when proc.ProcessEvents_exception do
task.part.logmgr.putline('ProcessEvents_exception');
processing = FALSE;
when task.shutdown do
exit;
end event;
end method;
method SomeService1.StartImmediate
begin
task.part.logmgr.putline(task.traceBack());
processing = TRUE;
start task proc.ProcessEvents() where completion =
event;
end method;
end CLASS;
SOMESERVICE2 CLASS
begin CLASS;
class SomeService2 inherits from Framework.Object
has public attribute proc: StartTaskTest.Processor;
has public attribute processing: Framework.boolean;
has public event StartProcessing;
has public method Init;
has public method ProcessingLoop;
has public method StartImmediate;
has property
shared=(allow=off, override=on);
transactional=(allow=off, override=on);
monitored=(allow=off, override=on);
distributed=(allow=on, override=on, default=off);
end class;
method SomeService2.Init
begin
super.Init();
processing = FALSE;
proc = new;
start task ProcessingLoop();
end method;
method SomeService2.ProcessingLoop
begin
timer : Timer = new;
timer.tickInterval = 10000;
event loop
task.part.logmgr.putline('processing loop
listening');
timer.isActive = TRUE;
when timer.tick do
StartImmediate();
when self.StartProcessing do
processing = TRUE;
start task proc.ProcessEvents() where completion =
event;
when proc.ProcessEvents_return do
task.part.logmgr.putline('ProcessEvents_return');
processing = FALSE;
when proc.ProcessEvents_exception do
task.part.logmgr.putline('ProcessEvents_exception');
processing = FALSE;
when task.shutdown do
exit;
end event;
end method;
method SomeService2.StartImmediate
begin
task.part.logmgr.putline(task.traceBack());
post StartProcessing;
end method;
end CLASS;
PROCESSOR CLASS
begin CLASS;
class Processor inherits from Framework.Object
has public method Init;
has public method ProcessEvents where completion =
(return = ProcessEvents_return, exception =
ProcessEvents_exception);
has property
shared=(allow=off, override=on);
transactional=(allow=off, override=on);
monitored=(allow=off, override=on);
distributed=(allow=off, override=on);
end class;
method Processor.Init
begin
super.Init();
end method;
method Processor.ProcessEvents
begin
task.part.logmgr.putline('Start processing...');
task.Delay(msecs = 1500);
task.part.logmgr.putline('Processing complete.');
end method;
end CLASS;
For the archives, go to: http://lists.xpedior.com/forte-users and use
the login: forte and the password: archive. To unsubscribe, send in a new
email the word: 'Unsubscribe' to: forte-users-requestlists.xpedior.com

Yes, you're right. The return event is queued until the moment that you
actually enter an eventloop. I stand corrected.
Pascal Rottier
Atos Origin Nederland (BAS/West End User Computing)
Tel. +31 (0)10-2661223
Fax. +31 (0)10-2661199
E-mail: Pascal.Rottiernl.origin-it.com
++++++++++++++++++++++++++++
Philip Morris (Afd. MIS)
Tel. +31 (0)164-295149
Fax. +31 (0)164-294444
E-mail: Rottier.Pascalpmintl.ch
-----Original Message-----
From: Adamek, Zenon [mailto:ZAdamekpurolator.com]
Sent: Thursday, January 18, 2001 6:13 PM
To: Rottier, Pascal
Cc: 'forte-userslists.xpedior.com'
Subject: RE: (forte-users) Confusion with return event
I think it is always safe to use start task with where complition = event
clause before event loop. The reason is described in Forte Help in the
Complition Clause index:
"Requesting the return and exception events automatically registers the
events for the calling task. When the asynchronous method completes or
terminates, Forté adds the appropriate event to the calling task's event
queue.
This registration is unlike the event registration for the event statement.
In the event statement, the event is registered just before the event
statement is ready to process the event. In the start task statement, the
return and exception events are registered when the task is started, even
though it can be much later on that your application is prepared to wait for
those events. Therefore, only the "parent" task that executes the start task
statement is registered for the completion event of the started task."
and some comments from "Forte Performance and Patterns" page 18:
"When you use the where completion = event clause in the start task
statement, Forte automatically buffer the return event until you register
for it. Therefore, you do not need to worry about the child task completing
before you register for its return event".
Regards,
Zenon
-----Original Message-----
From: Rottier, Pascal [SMTP:Rottier.Pascalpmintl.ch]
Sent: Thursday, January 18, 2001 11:16 AM
To: 'Samer Kanjo'; ForteUsers
Subject: RE: (forte-users) Confusion with return event
Yes, if you want the eventloop of the service object to be informed when
the
method on the processor class is invoked, regardless of who invoked it,
then
you should simply post an event as the last statement inside the method on
the processor class.
The return events are only used to inform a partent task that a child-task
has completed. So, only the calling task receives the event, only if the
calling task is inside an event-loop at the moment the child-task
terminates
and only if there really is a child task (method started using "start task
Note, that the calling task doesn't have to be inside an event loop when
the
asynchronous call is made. It has to be inside an eventloop when the
asynchronous task terminates. The following piece of code works just as
well:
SomeService1.StartImmediate();
self.DoSomeOtherStuff();
event loop
when SomeService1.Proc.ProcessEvent_return do
task.Part.Logmgr.Putline('ProcessEvents_return');
when SomeService1.Proc.ProcessEvent_exception do
task.Part.Logmgr.Putline('ProcessEvents_exception');
end event;
However, if the asynchronous task started from within "StartImmediate"
finishes before the client gets a chance to enter its event loop, then
you're too late to catch the event. That's why it's safer to use the
"postregister" function, which makes sure a certain action is not started
untill all events from the event loop have been registered.
Pascal Rottier
Atos Origin Nederland (BAS/West End User Computing)
Tel. +31 (0)10-2661223
Fax. +31 (0)10-2661199
E-mail: Pascal.Rottiernl.origin-it.com
++++++++++++++++++++++++++++
Philip Morris (Afd. MIS)
Tel. +31 (0)164-295149
Fax. +31 (0)164-294444
E-mail: Rottier.Pascalpmintl.ch
-----Original Message-----
From: Samer Kanjo [mailto:skanjoyahoo.com]
Sent: Thursday, January 18, 2001 5:04 PM
To: ForteUsers
Subject: RE: (forte-users) Confusion with return event
Pascal,
So you are confirming that a return event can only be
received in an event loop if a task is started from
within that event loop.
After making your proposed changes I was able to
receive the return event in the window.
I originally wanted the SomeService event loop to
always receive the return event regardless of whether
or not StartImmediate is called by some other entity
or called when the timer ticks. It seems that the only
way to do this is with events. Is that correct?
Thank you for insight,
Samer Kanjo
--- "Rottier, Pascal" <Rottier.Pascalpmintl.ch>
wrote:
Samer,
The return event is delivered to the calling task,
which is the window in
your first test. It is not deliverd to the event
loop of the service object
unless the call to the processor originated in the
event loop, which is the
case in your second test. The output you get from
the server is exactly as I
would expect.
You need the following code in you client:
event loop
postregister
SomeService1.StartImmediate();
when SomeService1.Proc.ProcessEvent_return do
task.Part.Logmgr.Putline('ProcessEvents_return');
when SomeService1.Proc.ProcessEvent_exception do
task.Part.Logmgr.Putline('ProcessEvents_exception');
end event;
Note that this logoutput will not be written to a
logfile, but will appear
in the logwindow which is opened when you start a
client application.
Pascal Rottier
Atos Origin Nederland (BAS/West End User Computing)
Tel. +31 (0)10-2661223
Fax. +31 (0)10-2661199
E-mail: Pascal.Rottiernl.origin-it.com
++++++++++++++++++++++++++++
Philip Morris (Afd. MIS)
Tel. +31 (0)164-295149
Fax. +31 (0)164-294444
E-mail: Rottier.Pascalpmintl.ch--
For the archives, go to: http://lists.xpedior.com/forte-users and use
the login: forte and the password: archive. To unsubscribe, send in a new
email the word: 'Unsubscribe' to: forte-users-requestlists.xpedior.com
For the archives, go to: http://lists.xpedior.com/forte-users and use
the login: forte and the password: archive. To unsubscribe, send in a new
email the word: 'Unsubscribe' to: forte-users-requestlists.xpedior.com

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