Override protected method as public
I am new to Java.
My doubt is :
I have a class named Base having one protected method(let's say x()) and another class named Derived which extends Base.
Now i want to override method x() of the Base class. Here I have 2 option either use access modifier as protected or public.
As per my understanding, i can override this method only with exact signature. But I can use Public as well. And here i am getting confused why we can.
Eg. In Object class we have method clone() which is protected, and to get cloned object of my class i need to override this method either with protected modifier or as public.
If I override as public then whats the use of protected method, why its not defined as public.
Please clear me the concept.
cool_kkin wrote:
As per my understanding, i can override this method only with exact signature. But I can use Public as well. And here i am getting confused why we can.Yes widening the scope is fine because the method still exists in the same nature as the method in the superclass. However narrowing the scope will hide for instance throw able exceptions from the caller, break polymorphism, conflict with the intension's of the class from the author and a whole wealth of other problems.
If I override as public then whats the use of protected method, why its not defined as public. Not every class is sub classed, therefore the protected declaration acts as it should. The final declaration can also be used in conjunction with protected, making subclasses unable to widen the scope of protected, or even override the method to begin with.
Mel
Similar Messages
-
Overriding a method which is protected
I have written a subclass 'B' to a parent class 'A' which is in different package than the parent class, but one of the method (almost same as parent classes method) which i have overridden in the subclass invokes a method (which has 'protected' access) of other classes say class 'C' of parent class package which will not work due to visibility. What is the best way to over come this problem. I have to override the code which is in the parent class.
a) Is it to create subclass of 'C' in the same package of class 'B' and override the method which is being called.
b) Is it to name the subclass package similar to the parent class Package.
Note : - Parent class package is in different project.If it's protected then either it was made that way for a good reason (to not let you invoke it, so -- success!), or not for a good reason (bad design).
The simple answer is you can't invoke that method as it currently stands, as you already know due to the compile time error message you're getting. If you're in control of its design and actually do need it to be accessed from outside its own package, then make it public. -
Is not abstract and does not override abstract method tablechanged
I will remove all the gui code to make it shorter, but my problem lies with my InteractiveTableModelListener.
public class Meet extends JPanel{
private static void createAndShowGUI() {
JFrame frame = new JFrame("MEET_dataTable");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new Meet(), BorderLayout.CENTER);
frame.pack();
frame.setVisible(true);
public class InteractiveTableModelListener implements TableModelListener {
public void TableChanged(TableModelEvent evt) {
if (evt.getType() == TableModelEvent.UPDATE) {
int column = evt.getColumn();
int row = evt.getFirstRow();
dataTable.setColumnSelectionInterval(column + 1, column + 1);
dataTable.setRowSelectionInterval(row, row);
class InteractiveRenderer extends DefaultTableCellRenderer {
protected int interactiveColumn;
public InteractiveRenderer(int interactiveColumn) {
this.interactiveColumn = interactiveColumn;
public Component getTableCellRendererComponent(JTable dataTable,
Object value, boolean isSelected, boolean hasFocus, int row,
int column)
Component c = super.getTableCellRendererComponent(dataTable, value, isSelected, hasFocus, row, column);
if (column == interactiveColumn && hasFocus) {
if ((Meet.this.tableModel.getRowCount() - 1) == row &&
!Meet.this.tableModel.hasEmptyRow())
Meet.this.tableModel.addEmptyRow();
highlightLastRow(row);
return c;
public void highlightLastRow(int row) {
int lastrow = tableModel.getRowCount();
if (row == lastrow - 1) {
dataTable.setRowSelectionInterval(lastrow - 1, lastrow - 1);
else {
dataTable.setRowSelectionInterval(row + 1, row + 1);
dataTable.setColumnSelectionInterval(0, 0);
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
UIManager.put("swing.boldMetal", Boolean.FALSE);
createAndShowGUI();
}As i say, i have removed all the gui code to make it shorter, but in this code i create the table and add all the model to it. I am being returned with the error
Meet.InteractiveTableModelListener is not abstract and does not override abstract method tableChanged(javax.swing.event.TableModelEvent)in javax.swing.event.TableModelListener
what would be causing this error?
CheersSorry, just figured out my silly error, the method is tableChanged not TableChanged.
cheers
TOPIC CLOSED
Edited by: nick2price on Sep 11, 2008 7:08 AM -
Not sure how to use protected method in arraylisy
Hi,
Im wondering how to use the removeRange method in java arraylist, its a protected method which returns void.
http://java.sun.com/j2se/1.3/docs/api/java/util/ArrayList.html#removeRange(int,%20int)
So if my class extends Arraylist i should be able to call the method but the compiler states that it still has protected access in arraylist. Does this mean im still overriding the method in arraylist ? A little explanation of whats happeneing would be appreciated as much as an answer
thanksIn this codefinal class myClass extends java.util.ArrayList {
private ArrayList array = new ArrayList();
public myClass(ArrayList ary){
for(int i=0;i<7;i++) {
array.add(ary.get(i));
ary.removeRange(0,7)
}You are defining a class called myClass which extends ArrayList.
You have a member variable called array which is an ArrayList
You have a constructor which takes a parameter called ary which is an ArrayList
Since ary is an ArrayList, you cannot call it's removeRange() method unless myClass is in the java.util package. Do not put your class in the java.util package.
It seems like what you want to do is to move the items in one ArrayList to another ArrayList rather than copying them. I wrote a program to do this. Here it isimport java.util.*;
public class Test3 {
public static void main(String[] args) {
MyClass myClass = new MyClass();
for (int i=0; i<5; i++) myClass.add("Item-"+i);
System.out.println("------ myClass loaded -------");
for (int i=0; i<myClass.size(); i++) System.out.println(myClass.get(i));
MyClass newClass = new MyClass(myClass);
System.out.println("------ newClass created -------");
for (int i=0; i<newClass.size(); i++) System.out.println(newClass.get(i));
System.out.println("------ myClass now contains -------");
for (int i=0; i<myClass.size(); i++) System.out.println(myClass.get(i));
class MyClass extends java.util.ArrayList {
public MyClass() {}
public MyClass(MyClass ary){
for(int i=0;i<ary.size();i++) add(ary.get(i));
ary.removeRange(0,ary.size());
}You should notice now that I don't create an ArrayList anywhere. Everything is a MyClass. By the way, class names are normally capitalized, variable names are not. Hence this line
MyClass myClass = new MyClass();
In the code above I create an empty MyClass and then populate it with 5 items and then print that list. Then I create a new MyClass using the constructor which takes a MyClass parameter. This copies the items from the parameter list into the newly created MyClass (which is an ArrayList) and then removes the items from the MyClass passed as a parameter. Back in the main() method, I then print the contents of the two MyClass objects.
One thing which may be a little confusing is this line.
for(int i=0;i<ary.size();i++) add(ary.get(i));
the add() call doesn't refer to anything. What it really refers to is the newly created MyClass object which this constructor is building. This newly created object is the 'this' object. So the line above could be rewritten as
for(int i=0;i<ary.size();i++) this.add(ary.get(i));
Hopefully this helps a little. The problems you seem to be having are associated with object oriented concepts. You might try reading this
http://sepwww.stanford.edu/sep/josman/oop/oop1.htm -
How to override a method in an inner class of the super class
I have a rather horribly written class, which I need to adapt. I could simply do this if I could override a method in one of it's inner classes. My plan then was to extend the original class, and override the method in question. But here I am struggling.
The code below is representative of my situation.
public class ClassA
ValueChecks vc = null;
/** Creates a new instance of Main */
public ClassA()
System.out.println("ClassA Constructor");
vc = new ValueChecks();
vc.checkMaximum();
// I want this to call the overridden method, but it does not, it seems to call
// the method in this class. probably because vc belongs to this class
this.vc.checkMinimum();
this.myMethod();
protected void myMethod()
System.out.println("myMethod(SUPER)");
protected class ValueChecks
protected boolean checkMinimum()
System.out.println("ValueChecks.checkMinimum (SUPER)");
return true;
protected boolean checkMaximum()
return false;
}I have extended ClassA, call it ClassASub, and it is this Class which I instantiate. The constructor in ClassASub obviously calls the constructor in ClassA. I want to override the checkMinimum() method in ValueChecks, but the above code always calls the method in ClassA. The ClassASub code looks like this
public class ClassASub extends ClassA
public ClassAInner cias;
/** Creates a new instance of Main */
public ClassASub()
System.out.println("ClassASub Constructor");
protected void myMethod()
System.out.println("myMethod(SUB)");
protected class ValueChecks extends ClassA.ValueChecks
protected boolean checkMinimum()
System.out.println("ValueChecks.checkMinimum (SUB)");
return true;
}The method myMethod seems to be suitably overridden, but I cannot override the checkMinimum() method.
I think this is a stupid problem to do with how the ValueChecks class is instantiated. I think I need to create an instance of ValueChecks in ClassASub, and pass a reference to it into ClassA. But this will upset the way ClassA works. Could somebody enlighten me please.vc = new ValueChecks();vc is a ValueChecks object. No matter whether you subclass ValueChecks or not, vc is always of this type, per this line of code.
// I want this to call the overridden method, but it does not, it seems to > call
// the method in this class. probably because vc belongs to this class
this.vc.checkMinimum();No, it's because again vc references a ValueChecks object, because it was created as such.
And when I say ValueChecks, I mean the original class, not the one you tried to create by the same name, attempting to override the original. -
Overriding redo method in drawing arrows
I have to undo and redo of path and arrows to them.at a time i need only either left arrow undo or right arrow undo depending on the direction in which path is drawn ie if its frm left to right then arrowhead left
and if its from right to left tthen arrowheadtright.
Undo is ok But problem comes with redo.Since if the last drawn path is from left to right then arrowright becomes null.pls suggest me a method overriding redo method for left and right arrows
private void redoButtonActionPerformed(java.awt.event.ActionEvent evt) {
try { m_edit.redo(); }
catch (CannotRedoException cre)
{ cre.printStackTrace(); }
drawpanel.repaint();
undoButton.setEnabled(m_edit.canUndo());
redoButton.setEnabled(m_edit.canRedo());
private void undoButtonActionPerformed(java.awt.event.ActionEvent evt) {
try { m_edit.undo(); }
catch (CannotRedoException cre)
{ cre.printStackTrace(); }
drawpanel.repaint();
undoButton.setEnabled(m_edit.canUndo());
redoButton.setEnabled(m_edit.canRedo());
class Edit extends AbstractUndoableEdit {
protected Vector drawarc;
protected Curve path;
protected Vector vectlabel;
protected drawlabel labelarc;
protected Vector arrowheadleft;
protected drawArrowHeads arrow1;
protected Vector arrowheadright;
protected drawArrowHeadsecond arrow2;
public Edit( Vector drawarc, Curve path ,Vector vectlabel,drawlabel labelarc,Vector arrowheadleft,drawArrowHeads arrow1,Vector arrowheadright,drawArrowHeadsecond arrow2)
this.drawarc = drawarc;
this.path = path;
this.vectlabel=vectlabel;
this.labelarc=labelarc;
this.arrowheadleft=arrowheadleft;
this.arrow1=arrow1;
this.arrowheadright=arrowheadright;
this.arrow2=arrow2;
public void undo() throws CannotUndoException {
drawarc.remove(path);
vectlabel.remove(labelarc);
arrowheadleft.remove(arrow1);
arrowheadright.remove(arrow2);
public void redo() throws CannotRedoException {
drawarc.add( path);
vectlabel.add(labelarc);
// arrowheadleft.add(arrow1);
// System.out.println("The arrowheadleft vector inside Edit method contains "+arrowheadleft.toString());
arrowheadright.add(arrow2);
System.out.println("The arrowheadright vector inside Edit method contains "+arrowheadright.toString());
public boolean canUndo() {
return true;
public boolean canRedo() {
return true;
public String getPresentationName() {
return "Add Arc";
m_edit=new Edit(drawarc, path , vectlabel, labelarc, arrowheadleft, arrow1, arrowheadright, arrow2);
undoButton.setText(m_edit.getUndoPresentationName());
redoButton.setText(m_edit.getRedoPresentationName());
undoButton.setEnabled(m_edit.canUndo());
redoButton.setEnabled(m_edit.canRedo());..arrowright becomes null..Check for null value. If null, then do nothing with it.
-
Overriding toString method of entrySet() in LinkedHashMap
Hi all,
I got a LinkedHashMap which return a Set by entrySet() method. When I print the String represantation of the returned Set, I receive something like [key=value, key=value, key= value]. I, however, would like to override toString method so that I can implement my own representation of the Set class which is returned by entrySet() method. How can I do that if it's possible?i believe what Peter was saying was to overrider the Set (in your case...the concrete LinkedhashSet class)
you're not implementing the add, get, contains, etc..function..you're extending it.
after extending it..you can overide any public and protected method...any other method not overide is still there for you to use.
so you would have something like this
public class MyLinkHashSet extends LinkHashSet{
public String toString(){
return a String representation you want
public Object getMyObject(){ return myObject; } // your own method
// you still have all of the other LinkHashSet methods to use
} -
Calling protected method in inheritance heirarchy
Hi All,
How can I call to super.super.method if the method is protected?
The method was overided in each class of the heirarchy.If you think you need to do that, you have a flawed design. Each subclass extends its parent class and may invoke the super implementation, but not the implementation in the superclass's superclass.
This is possible:class SuperSuper {
protected void method() {
System.out.println("In SuperSuper.method");
class Super extends SuperSuper {
@Override
protected void method() {
super.method();
System.out.println("In Super");
class Sub extends Super {
@Override
protected void method() {
super.method();
System.out.println("In Sub");
public static void main(String[] args) {
new Sub().method();
}db -
Hi again!
I know that to override an instance metothd i have to do like this:
super.instanceMethod(parameters)
My instance method it's this:
protected function clickListener(e:Event = null):void{
//reference to the Container
container = MovieClip(e.currentTarget)
//reference to the button
activeButton = MovieClip(e.target)
//reference to the Container name
containerName = String((e.currentTarget).name);
Override:
override protected function clickListener(e:Event = null):void{
//call the overridden method
super.clickListener(e)
what if in the overriden method i wnt to change just:
container = MovieClip(e.currentTarget)
to:
container = MovieClip(e.target)
e leave the other method variable?
thanks!!Do just:
override protected function clickListener(e:Event = null):void {
super.clickListener(e)
container = MovieClip(e.target)
Given that container is either public or protected property. -
Is not abstract and does not override abstract method actionPerformed
I dont how to corr. Please help!! and thank you very much!!
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class test extends JFrame implements ActionListener, ItemListener
private CenterPanel centerPanel;
private QuestionPanel questionPanel;
private ButtonPanel buttonPanel;
private ResponsePanel responsePanel;
private JButton b1,b2,b3,b4,b5; //Create five references to Jbutton instances
private JTextField t1,t2,t3,t4,t5; //Create five references to JTextField instances
private JLabel label1; //Create one references to JLabel instances
private JRadioButton q1,q2,q3; //Create three references to JRadioButton instances
private ButtonGroup radioGroup; //Create one references to Button Group instances
private int que1[] = new int[5]; //Create int[4] Array
private int que2[] = new int[5];
private int que3[] = new int[5];
private String temp1, temp2, temp3, temp4, temp5, temp6, temp7, temp8, temp9, temp10,
temp11, temp12, temp13, temp14, temp15;
public test (String header)
super(header);
Container container = getContentPane();
label1 = new JLabel ("PLease click on your response to ");
q1 = new JRadioButton("I understand most of the content of this subject",true);
add(q1);
q2 = new JRadioButton("I see the relevance of the subject to my degree",false);
add(q2);
q3 = new JRadioButton("The workload in this subject is appropriate",false);
add(q3);
radioGroup = new ButtonGroup(); //JRadioButton belong to ButtonGroup
radioGroup.add(q1);
radioGroup.add(q2);
radioGroup.add(q3);
JPanel buttonPanel = new JPanel();
JPanel responsePanel = new JPanel();
JPanel questionPanel = new JPanel();
JPanel centerPanel = new JPanel();
b1 = new JButton ("Strongly DISAGREE"); //Instantiate JButton with text
b1.addActionListener (this); //Register JButtons to receive events
b2 = new JButton ("DISAGREE");
b2.addActionListener (this);
b3 = new JButton ("Neither AGREE or DISAGREE");
b3.addActionListener (this);
b4 = new JButton ("AGREE");
b4.addActionListener (this);
b5 = new JButton ("Strongly AGREE");
b5.addActionListener (this);
buttonPanel.setLayout(new GridLayout(5,1));
buttonPanel.add(b1);
buttonPanel.add(b2);
buttonPanel.add(b3);
buttonPanel.add(b4);
buttonPanel.add(b5);
t1 = new JTextField ("0",3); //JTextField contains empty string
t2 = new JTextField ("0",3);
t3 = new JTextField ("0",3);
t4 = new JTextField ("0",3);
t5 = new JTextField ("0",3);
t1.setEditable( false );
t2.setEditable( false );
t3.setEditable( false );
t4.setEditable( false );
t5.setEditable( false );
responsePanel.setLayout(new GridLayout(5,1));
responsePanel.add(t1);
responsePanel.add(t2);
responsePanel.add(t3);
responsePanel.add(t4);
responsePanel.add(t5);
questionPanel.setLayout(new GridLayout(4,1));
questionPanel.add(label1);
questionPanel.add(q1);
questionPanel.add(q2);
questionPanel.add(q3);
centerPanel.add(buttonPanel,BorderLayout.CENTER);
centerPanel.add(responsePanel,BorderLayout.EAST);
container.add(centerPanel,BorderLayout.WEST);
container.add(questionPanel,BorderLayout.NORTH);
q1.addActionListener(
new ActionListener(){
public void actionPerformed( ActionEvent e )
{ //actionPerformed of all registered listeners
if (e.getSource() == b1) {
que1[0] = Integer.parseInt(t1.getText()) + 1;
String temp1 = String.valueOf(que1[0]);
t1.setText(temp1);
else if (e.getSource() == b2) {
que1[1] = Integer.parseInt(t2.getText()) + 1;
String temp2 = String.valueOf(que1[1]);
t2.setText(temp2);
else if (e.getSource() == b3) {
que1[2] = Integer.parseInt(t3.getText()) + 1;
String temp3 = String.valueOf(que1[2]);
t3.setText(temp3);
else if (e.getSource() == b4) {
que1[3] = Integer.parseInt(t4.getText()) + 1;
String temp4 = String.valueOf(que1[3]);
t4.setText(temp4);
else if (e.getSource() == b5) {
que1[4] = Integer.parseInt(t5.getText()) + 1;
String temp5 = String.valueOf(que1[4]);
t5.setText(temp5);
} //end action performed
q2.addActionListener(
new ActionListener(){
public void actionPerformed( ActionEvent e )
{ //actionPerformed of all registered listeners
if (e.getSource() == b1) {
que2[0] = Integer.parseInt(t1.getText()) + 1;
String temp6 = String.valueOf(que2[0]);
t1.setText(temp1);
else if (e.getSource() == b2) {
que2[1] = Integer.parseInt(t2.getText()) + 1;
String temp7 = String.valueOf(que2[1]);
t2.setText(temp7);
else if (e.getSource() == b3) {
que2[2] = Integer.parseInt(t3.getText()) + 1;
String temp8 = String.valueOf(que2[2]);
t3.setText(temp8);
else if (e.getSource() == b4) {
que2[3] = Integer.parseInt(t4.getText()) + 1;
String temp9 = String.valueOf(que2[3]);
t4.setText(temp9);
else if (e.getSource() == b5) {
que2[4] = Integer.parseInt(t5.getText()) + 1;
String temp10 = String.valueOf(que2[4]);
t5.setText(temp10);
} //end action performed
q3.addActionListener(
new ActionListener(){
public void actionPerformed( ActionEvent e )
{ //actionPerformed of all registered listeners
if (e.getSource() == b1) {
que3[0] = Integer.parseInt(t1.getText()) + 1;
String temp11 = String.valueOf(que3[0]);
t1.setText(temp11);
else if (e.getSource() == b2) {
que3[1] = Integer.parseInt(t2.getText()) + 1;
String temp12 = String.valueOf(que3[1]);
t2.setText(temp12);
else if (e.getSource() == b3) {
que3[2] = Integer.parseInt(t3.getText()) + 1;
String temp13 = String.valueOf(que3[2]);
t3.setText(temp13);
else if (e.getSource() == b4) {
que3[3] = Integer.parseInt(t4.getText()) + 1;
String temp14 = String.valueOf(que3[3]);
t4.setText(temp14);
else if (e.getSource() == b5) {
que3[4] = Integer.parseInt(t5.getText()) + 1;
String temp15 = String.valueOf(que3[4]);
t5.setText(temp15);
} //end action performed
}//end constructor test
public void itemStateChanged(ItemEvent item) {
//int state = item.getStateChange();
//if (q1 == item.SELECTED)
public class ButtonPanel extends JPanel
public ButtonPanel()
public class CenterPanel extends JPanel
public CenterPanel()
public class QuestionPanel extends JPanel
public QuestionPanel()
public class ResponsePanel extends JPanel
public ResponsePanel()
public static void main(String [] args)
test surveyFrame = new test("Student Survey") ;
surveyFrame.setSize( 500,300 );
surveyFrame.setVisible(true);
surveyFrame.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);
}//end main
}//end class testis not abstract and does not override abstract method actionPerformed
Oh, I see that the title of your post is an error message? Ok. Well, the test class is declared as implementing an ActionListener. That means the test class must have an actionPerformed() method. Your test class apparently does not.
It does not appear that the test class needs to implement ActionListener. You are using annonymous classes as listeners. -
Is not abstract and does not override abstract method ERROR
Hello. I'm new at all this, and am attempting to recreate a sample code out of my book (Teach Yourself XML in 24 Hours), and I keep getting an error. I appriciate any help.
This is the Error that I get:
DocumentPrinter is not abstract and does not override abstract method skippedEntity(java.lang.String) in org.xml.sax.ContentHandler
public class DocumentPrinter implements ContentHandler, ErrorHandler
^This is the sourcecode:
import org.xml.sax.Attributes;
import org.xml.sax.ContentHandler;
import org.xml.sax.ErrorHandler;
import org.xml.sax.Locator;
import org.xml.sax.SAXParseException;
import org.xml.sax.XMLReader;
public class DocumentPrinter implements ContentHandler, ErrorHandler
// A Constant containing the name of the SAX parser to use.
private static final String PARSER_NAME = "org.apache.xerces.parsers.SAXParser";
public static void main(String[] args)
// Check to see whether the user supplied any command line arguments. If not, print an error and exit.
if (args.length == 0)
System.out.println("No XML document path specified.");
System.exit(1);
// Create a new instance of the DocumentPrinter class.
DocumentPrinter dp = new DocumentPrinter();
try
// Create a new instance of the XML Parser.
XMLReader parser = (XMLReader)Class.forName(PARSER_NAME).newInstance();
// Set the parser's content handler
// parser.setContentHandler(dp);
// Set the parsers error handler
parser.setErrorHandler(dp);
// Parse the file named in the argument
parser.parse(args[0]);
catch (Exception ex)
System.out.println(ex.getMessage());
ex.printStackTrace();
public void characters(char[] ch, int start, int length)
String chars ="";
for (int i = start; i < start + length; i++)
chars = chars + ch;
System.out.println("Recieved characters: " + chars);
public void startDocument()
System.out.println("Start Document.");
public void endDocument()
System.out.println("End of Document.");
public void startElement(String namespaceURI, String localName, String qName, Attributes atts)
System.out.println("Start element: " + localName);
for (int i = 0; i < atts.getLength(); i++)
System.out.println(" Attribute: " + atts.getLocalName(i));
System.out.println(" Value: " + atts.getValue(i));
public void endElement(String namespaceURI, String localName, String qName)
System.out.println("End of element: " + localName);
public void startPrefixMapping(String prefix, String uri)
System.out.println("Prefix mapping: " + prefix);
System.out.println("URI: " + uri);
public void endPrefixMapping(String prefix)
System.out.println("End of prefix mapping: " + prefix);
public void ignorableWhitespace(char[] ch, int start, int length)
System.out.println("Recieved whitespace.");
public void processingInstruction(String target, String data)
System.out.println("Recieved processing instruction:");
System.out.println("Target: " + target);
System.out.println("Data: " + data);
public void setDocumentLocation(Locator locator)
// Nada
public void error(SAXParseException exception)
System.out.println("Parsing error on line " + exception.getLineNumber());
public void fatalError(SAXParseException exception)
System.out.println("Fatal parsing error on line " + exception.getLineNumber());
public void warning(SAXParseException exception)
System.out.println("Warning on line " + exception.getLineNumber());Check to make sure that the arguments are consistent with your ContentHandler class. Probably the wrong type.
I think you forgot to include the skippedEntity method, it seems to be missing. Even if an implemented class has a method that you are not using, you still have to include the method in your code even if it doesn't do anything.
Message was edited by:
ChargersTule1 -
...is not abstract and does not override abstract method compare
Why am I getting the above compile error when I am very clearly overriding abstract method compare (ditto abstract method compareTo)? Here is my code -- which was presented 1.5 code and I'm trying to retrofit to 1.4 -- followed by the complete compile time error. Thanks in advance for your help (even though I'm sure this is an easy question for you experts):
import java.util.*;
This program sorts a set of item by comparing
their descriptions.
public class TreeSetTest
public static void main(String[] args)
SortedSet parts = new TreeSet();
parts.add(new Item("Toaster", 1234));
parts.add(new Item("Widget", 4562));
parts.add(new Item("Modem", 9912));
System.out.println(parts);
SortedSet sortByDescription = new TreeSet(new
Comparator()
public int compare(Item a, Item b) // LINE CAUSING THE ERROR
String descrA = a.getDescription();
String descrB = b.getDescription();
return descrA.compareTo(descrB);
sortByDescription.addAll(parts);
System.out.println(sortByDescription);
An item with a description and a part number.
class Item implements Comparable
Constructs an item.
@param aDescription the item's description
@param aPartNumber the item's part number
public Item(String aDescription, int aPartNumber)
description = aDescription;
partNumber = aPartNumber;
Gets the description of this item.
@return the description
public String getDescription()
return description;
public String toString()
return "[descripion=" + description
+ ", partNumber=" + partNumber + "]";
public boolean equals(Object otherObject)
if (this == otherObject) return true;
if (otherObject == null) return false;
if (getClass() != otherObject.getClass()) return false;
Item other = (Item) otherObject;
return description.equals(other.description)
&& partNumber == other.partNumber;
public int hashCode()
return 13 * description.hashCode() + 17 * partNumber;
public int compareTo(Item other) // OTHER LINE CAUSING THE ERROR
return partNumber - other.partNumber;
private String description;
private int partNumber;
}Compiler error:
TreeSetTest.java:25: <anonymous TreeSetTest$1> is not abstract and does not over
ride abstract method compare(java.lang.Object,java.lang.Object) in java.util.Com
parator
public int compare(Item a, Item b)
^
TreeSetTest.java:41: Item is not abstract and does not override abstract method
compareTo(java.lang.Object) in java.lang.Comparable
class Item implements Comparable
^
2 errorsAccording to the book I'm reading, if you merely take
out the generic from the code, it should compile and
run in v1.4 (assuming, of course, that the class
exists in 1.4). I don't know what book you are reading but that's certainly incorrect or incomplete at least. I've manually retrofitted code to 1.4, and you'll be inserting casts as well as replacing type references with Object (or the erased type, to be more precise).
These interfaces do exist in 1.4, and
without the generics.Exactly. Which means compareTo takes an Object, and you should change your overriding method accordingly.
But this raises a new question: how does my 1.4
compiler know anything about generics? It doesn't and it can't. As the compiler is telling you, those interfaces expect Object. Think about it, you want to implement one interface which declares a method argument type of Object, in several classes, each with a different type. Obviously all of those are not valid overrides. -
Product is not abstract and does not override abstract method
Received the following errors.
Product.java:3: Product is not abstract and does not override abstract method ge
tDisplayText() in Displayable
public class Product implements Displayable
^
Product.java:16: getDisplayText() in Product cannot implement getDisplayText() i
n Displayable; attempting to use incompatible return type
found : void
required: java.lang.String
public void getDisplayText()
^
2 errors
Code reads as follows
import java.text.NumberFormat;
public class Product implements Displayable
private String code;
private String description;
private double price;
public Product()
this.code = "";
this.description = "";
this.price = 0;
public void getDisplayText()
String message =
"Code: " + code + "\n" +
"Description: " + description + "\n" +
"Price: " + this.getFormattedPrice() + "\n";
public Product(String code, String description, double price)
this.code = code;
this.description = description;
this.price = price;
public void setCode(String code)
this.code = code;
public String getCode(){
return code;
public void setDescription(String description)
this.description = description;
public String getDescription()
return description;
public void setPrice(double price)
this.price = price;
public double getPrice()
return price;
public String getFormattedPrice()
NumberFormat currency = NumberFormat.getCurrencyInstance();
return currency.format(price);
Please help!Received the following errors.
Product.java:3: Product is not abstract and does not
override abstract method ge
tDisplayText() in Displayable
public class Product implements Displayable
^
Product.java:16: getDisplayText() in Product cannot
implement getDisplayText() i
n Displayable; attempting to use incompatible return
type
found : void
required: java.lang.String
public void getDisplayText()
^
2 errors
Code reads as follows
Please use the code tags when posting code. There is a code button right above the text box where you enter your post. Click on it and put the code between the code tags.
These error messages are quite clear in telling what is wrong. You have an Interface called Displayable that specifies a method something like thispublic String getDisplayText() {But in your Product source code, you created thismethodpublic void getDisplayText() {The compiler is complaining because the methods are not the same.
You also need to return a String in the method probalby like thisreturn message; -
ALV - access to protected method
Hello,
I have a object from class "CL_GUI_ALV_GRID" and want to change the protected attribute "EVT_DELAYED_CHANGE_SELECTION Constant Protected" with the method
CALL METHOD alv_grid->SET_DELAY_CHANGE_SELECTION
EXPORTING
time = lv_delay.
How can I access this protected attribute?
Thanks in advance,
HolgerThis will do what you want
Trick is to define a sub class inheriting the super class where the protected attributes and methods exist in - then you can access the protected methods and attributes.
If you do this don't forget to call the SUPER CONSTRUCTOR (of the class you are inheriting from) in your constructor method. Code example shown below.
Here I want the original and modified table of an alv grid but you can adapt this code to whatever you need.
Hope it helps.
create blank screen (100) with a custom container CCONTAINER1 and the following scren logic in it
PROCESS BEFORE OUTPUT.
MODULE STATUS_0100.
PROCESS AFTER INPUT.
MODULE USER_COMMAND_0100.
now look at the code here. Note text in Bold
PROGRAM zdynfieldcat.
class zcltest definition deferred. "For field symbol reference.
Simple test of dynamic ITAB with user defined (not ddic) fields
Build dynamic fcat
Table structure obtained via new RTTI functionality
use ALV grid to display and edit.
Create a blank screen 100 with a custom container called CCONTAINER1.
James Hawthorne
Define field symbols as these can't be defined in classes
field-symbols: <dyn_table> type standard table,
<g2> type ref to zcltest,
<g1> type ref to cl_gui_custom_container,
<actual_tab> type standard table,
<outtab> type table,
<fs1> type ANY,
<FS2> TYPE TABLE,
<fs3> type table,
<fs4> type table,
<fs5> type table.
<b>class zcltest definition inheriting from cl_gui_alv_grid.
define this as a subclass so we can access the protected attributes
of the superclass cl_gui_alv_grid</b>
public section.
types: g4 type ref to cl_gui_custom_container.
types: g3 type ref to cl_alv_changed_data_protocol.
data: i_parent type g4,
lr_rtti_struc TYPE REF TO cl_abap_structdescr, "RTTI
zog like line of lr_rtti_struc->components. "RTTI
types: struc like zog.
types: struc1 type table of struc.
methods:
constructor
importing i_parent type g4,
disp_tab
importing p_er_data_changed type g3,
create_dynamic_fcat
importing zogt type struc1
exporting it_fldcat type lvc_t_fcat.
Protected section.
data: stab type ref to data,
wa_it_fldcat type lvc_s_fcat,
c_index type sy-index.
endclass.
<b>class zcltest implementation.
METHOD constructor.
CALL METHOD super->constructor
EXPORTING
i_appl_events = 'X'
i_parent = i_parent.
endmethod
method disp_tab.
*mt_outtab is the data table held as a protected attribute
in class cl_gui_alv_grid.
assign me->mt_outtab->* TO <outtab>. "Original data
assign p_er_data_changed->mp_mod_rows TO <FS1>.
stab = p_er_data_changed->mp_mod_rows.
assign p_er_data_changed->mt_inserted_rows to <fs3>.
assign p_er_data_changed->mt_deleted_rows to <fs4>.
assign p_er_data_changed->mt_mod_cells to <fs5>.
assign stab->* TO <fs2>.
do whatever you want with <outtab>
contains data BEFORE changes each time.
Note that NEW (Changed) table has been obtained already by
call to form check_data USING P_ER_DATA_CHANGED
TYPE REF TO CL_ALV_CHANGED_DATA_PROTOCOL.
Entered data is in table defined by <fs2>
In this method you can compare original and changed data.
Easier than messing around with individual cells.
do what you want with data in <fs2> validate / update / merge etc
endmethod.</b>
method create_dynamic_fcat.
loop at zogt into zog.
c_index = c_index + 1.
clear wa_it_fldcat.
wa_it_fldcat-fieldname = zog-name .
wa_it_fldcat-datatype = zog-type_kind.
wa_it_fldcat-inttype = zog-type_kind.
wa_it_fldcat-intlen = zog-length.
wa_it_fldcat-decimals = zog-decimals.
wa_it_fldcat-coltext = zog-name.
wa_it_fldcat-lowercase = 'X'.
if c_index eq 2.
wa_it_fldcat-emphasize = 'C411'.
endif.
if c_index eq 3.
wa_it_fldcat-emphasize = 'C511'.
endif.
append wa_it_fldcat to it_fldcat .
endloop.
endmethod. "create_dynamic_fcat
endclass. "zcltest IMPLEMENTATION
class lcl_grid_event_receiver definition.
public section.
methods:
handle_data_changed
for event data_changed of zcltest
for event data_changed of cl_gui_alv_grid
importing er_data_changed,
toolbar
for event toolbar of zcltest
importing e_object
e_interactive,
user_command
for event user_command of zcltest
importing e_ucomm.
endclass.
class lcl_grid_event_receiver implementation.
method handle_data_changed.
code whatever required after data entry.
various possibilites here as you can get back Cell(s) changed
columns or the entire updated table.
Data validation is also possible here.
call method <g2>->disp_tab
EXPORTING
p_er_data_changed = er_data_changed.
endmethod. "handle_data_changed
method toolbar.
data : ls_toolbar type stb_button.
clear ls_toolbar.
move 0 to ls_toolbar-butn_type.
move 'EDIT' to ls_toolbar-function.
move space to ls_toolbar-disabled.
move 'Edit' to ls_toolbar-text.
move icon_change_text to ls_toolbar-icon.
move 'Click2Edit' to ls_toolbar-quickinfo.
append ls_toolbar to e_object->mt_toolbar.
clear ls_toolbar.
move 0 to ls_toolbar-butn_type.
move 'UPDA' to ls_toolbar-function.
move space to ls_toolbar-disabled.
move 'Update' to ls_toolbar-text.
move icon_system_save to ls_toolbar-icon.
move 'Click2Update' to ls_toolbar-quickinfo.
append ls_toolbar to e_object->mt_toolbar.
clear ls_toolbar.
move 0 to ls_toolbar-butn_type.
move 'EXIT' to ls_toolbar-function.
move space to ls_toolbar-disabled.
move 'Exit' to ls_toolbar-text.
move icon_system_end to ls_toolbar-icon.
move 'Click2Exit' to ls_toolbar-quickinfo.
append ls_toolbar to e_object->mt_toolbar.
endmethod. "toolbar
method user_command.
case e_ucomm .
when 'EDIT'. "From Tool bar
perform set_input.
perform init_grid.
when 'UPDA'. "From Tool bar
perform refresh_disp.
perform update_table.
when 'EXIT'. "From Tool bar
leave program.
endcase.
endmethod. "user_command
endclass. "lcl_grid_event_receiver IMPLEMENTATION
program data
include <icon>.
define any old internal structure NOT in DDIC
types: begin of s_elements,
anyfield1(20) type c,
anyfield2(20) type c,
anyfield3(20) type c,
anyfield4(20) type c,
anyfield5(11) type n,
end of s_elements.
data: wa_element type s_elements,
wa_data type s_elements.
Note new RTTI functionality allows field detail retrieval
at runtime for dynamic tables.
data:
grid1 type ref to zcltest,
grid_handler type ref to lcl_grid_event_receiver,
c_dec2 type s_elements-anyfield5,
wa_it_fldcat type lvc_s_fcat,
it_fldcat type lvc_t_fcat,
lr_rtti_struc TYPE REF TO cl_abap_structdescr, "RTTI
lt_comp TYPE cl_abap_structdescr=>component_table,"RTTI
ls_comp LIKE LINE OF lt_comp, "RTTI
zog like line of lr_rtti_struc->components, "RTTI
struct_grid_lset type lvc_s_layo,
l_valid type c,
new_table type ref to data.
types: struc like zog.
data: zogt type table of struc,
grid_container1 type ref to cl_gui_custom_container,
g_event_receiver type ref to lcl_grid_event_receiver,
ok_code like sy-ucomm,
i4 type int4.
start-of-selection.
call screen 100.
module status_0100 output.
if grid_container1 is initial.
create object grid_container1
exporting
container_name = 'CCONTAINER1'.
assign grid_container1 to <g1>.
create object grid1
exporting i_parent = grid_container1.
we need reference to this instance so we can use
Methods etc of zcltest class and alv (superclass)
in our event receiver class.
assign grid1 to <g2>.
create object grid_handler.
set handler:
grid_handler->user_command for grid1,
grid_handler->toolbar for grid1,
grid_handler->handle_data_changed for grid1.
Get the Internal table structure
lr_rtti_struc ?= cl_abap_structdescr=>describe_by_data( wa_data ).
Build field catalog just use basic data here
colour specific columns as well
zogt[] = lr_rtti_struc->components.
call method grid1->create_dynamic_fcat
EXPORTING
zogt = zogt
IMPORTING
it_fldcat = it_fldcat.
Create dynamic internal table and assign to field symbol.
Use dynamic field catalog just built.
call method cl_alv_table_create=>create_dynamic_table
EXPORTING
it_fieldcatalog = it_fldcat
IMPORTING
ep_table = new_table.
assign new_table->* to <dyn_table>.
perform populate_dynamic_itab.
perform init_grid.
perform register_enter_event.
set off ready for input initially
i4 = 0.
call method grid1->set_ready_for_input
EXPORTING
i_ready_for_input = i4.
endif.
endmodule. "status_0100 OUTPUT
module user_command_0100 input.
*PAI not needed in OO ALV anymore as User Commands are handled as events
*in method user_command.
*we can also get control if the Data entered and the ENTER is pressed by
*raising an event.
Control then returns to method handle_data_changed.
endmodule. "user_command_0100 INPUT
form populate_dynamic_itab.
load up a line of the dynamic table
c_dec2 = c_dec2 + 11.
wa_element-anyfield1 = 'Tabbies'.
wa_element-anyfield2 = 'ger.shepards'.
wa_element-anyfield3 = 'White mice'.
wa_element-anyfield4 = 'Any old text'.
wa_element-anyfield5 = c_dec2.
append wa_element to <dyn_table>.
endform. "populate_dynamic_itab
form exit_program.
call method grid_container1->free.
call method cl_gui_cfw=>flush.
leave program.
endform. "exit_program
form refresh_disp.
call method grid1->refresh_table_display.
endform. "refresh_disp
form update_table.
The dynamic table here is the changed table read from the grid
after user has changed it
Data can be saved to DB or whatever.
loop at <dyn_table> into wa_element.
do what you want with the data here
endloop.
switch off edit mode again for next function
i4 = 0.
call method grid1->set_ready_for_input
EXPORTING
i_ready_for_input = i4.
endform. "update_table
form set_input.
i4 = 1.
call method grid1->set_ready_for_input
EXPORTING
i_ready_for_input = i4.
endform. "set_input
form switch_input.
if i4 = 1.
i4 = 0.
else.
i4 = 1.
endif.
call method grid1->set_ready_for_input
EXPORTING
i_ready_for_input = i4.
endform. "switch_input
form init_grid.
Enabling the grid to edit mode,
struct_grid_lset-edit = 'X'. "To enable editing in ALV
struct_grid_lset-grid_title = 'Jimbos Test'.
call method grid1->set_table_for_first_display
EXPORTING
is_layout = struct_grid_lset
CHANGING
it_outtab = <dyn_table>
it_fieldcatalog = it_fldcat.
endform. "init_grid
form register_enter_event.
call method grid1->register_edit_event
EXPORTING
i_event_id = cl_gui_alv_grid=>mc_evt_enter.
Instantiate the event or it won't work.
create object g_event_receiver.
set handler g_event_receiver->handle_data_changed for grid1.
endform. "register_enter_event -
In Java it is simple to extend a class and override a method - the whole idea of polymorphism. In abap, I'm attempting to do the same, but don't know quite how. I've created as a demo a zclass and made a sap standard class its superclass in properties. How do I override a protected method from here?
Marcin says:
Unfortunatelly overriding is not possible in ABAP, only redefinition is allowed. The method singature must stay the same in all subsequent classes.
I guess,
Overriding - Redefinition of the implementation of inherited method. This is possible by addition REDEFINITION to the method.
Overloading - Changing the method parameters of inherited method
Regards,
Naimesh Patel
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