Phillipe Rodrigues

Hi,
Please let me know the purpose of the below command

<copy file="ABC.zip " todir="."/>


What todir="." does?

Hi,
I'm new to java.I'm reading SCJP1.5 by Kathy.
Please help me in understanding the below with an example


The equals() method in class Object uses only the == operator for comparisons,
so unless you override equals(), two objects are considered equal only if the two
references refer to the same object.
Let's look at what it means to not be able to use an object as a hashtable key.
Imagine you have a car, a very specific car (say, John's red Subaru Outback as
opposed to Mary's purple Mini) that you want to put in a HashMap (a type of
hashtable we'll look at later in this chapter), so that you can search on a particular
car and retrieve the corresponding Person object that represents the owner. So you
add the car instance as the key to the HashMap (along with a corresponding Person
object as the value). But now what happens when you want to do a search? You want
to say to the HashMap collection, "Here's the car, now give me the Person object
that goes with this car." But now you're in trouble unless you still have a reference
to the exact object you used as the key when you added it to the Collection. In other
words, you can't make an identical Car object and use it for the search.
The bottom line is this: if you want objects of your class to be used as keys for a
hashtable (or as elements in any data structure that uses equivalency for searching
for�and/or retrieving�an object), then you must override equals() so that two
different instances can be considered the same.

How to get a date format in (dd-MON-CCYY) by writing a query in oracle.

CC- Century

Hi,
Request a query in oracle on how to convert rows into columns?

Reason being consider below example:

Table A:

Colunms: name, id
Values: john,1
shan,2
jimmy,3

table B:
Columns:id,roll no
1,23
2,24
3,25

Now the result displayed should be as below;
name name name rollno rollno rollno
John Shan Jimmy 23 24 25


Request your help.

when i click on MyEclipse 6.0 problem 2 different instances of myeclipse open.

What could be the reason?

Can we check for dynamically entered fields against one those exists in the table using SQL and not using PLSQL(Procedures,Functions,Cursors etc)?

I am not able to resolve the below error when I try executing the project.
java(jre) libraries include as default in a jav project.I am using eclipse 3.1 with java 1.4.2_06.

The resource is not on the build path of a Java project


What could be the possible cause.

What is the best book to refer for Eclipse3.It should include the configuration settings for the Java,J2EE development and explanation of the tabs maintained in the IDE,how and what its purpose while working out with the development.

Please suggest.

What is the best way to learn javascript? the reason being i try examples given in the book and run it successfully but i dont hoe to embed it with the JSP pages and how to check or write the code for the client side validation. how and when it invokes?

What does path id, classpath refid denotes?

<project ... >
<path id="project.class.path"> ...............(1)
<pathelement location="lib/"/>
<pathelement path="${java.class.path}/"/>
<pathelement path="${additional.path}"/>
</path>

<target ... >
<rmic ...>
<classpath refid="project.class.path"/>.....(2)
</rmic>
</target>

<target ... >
<javac ...>
<classpath refid="project.class.path"/>
</javac>
</target>
</project>

What about the below line numbers for the below code.When do we use them.What could be the possible cause for assiging class objects to an interface reference?

interface IStack{ public void push(); public Object pop(); } class StackImpl implements Istack{ public void push(){ some code written } public Object pop(){ return Object; } interface ISafeStack extends IStack{ boolean isEmpty(); } class IStackImpl extends StackImpl implements ISafeStack{ some code written } class Main_impl{ public staticc void main(String[] args){ IStackImpl one =new IStackImpl(); StackImpl two =one;....................(1) ISafeStack three =one;.................(2) IStack four =one;......................(3) } }

I am a bit confused on the following:

Collection is an interface and ArrayList is a concrete class.Then

Collection c =new ArrayList(); ......................(1)

How above(1) is posible as interface objects cannot be created.What could be the idea behind the above instruction(1)

What the below means?

A constructor in a subclass can access the class's inherited members directly. The keyword super can also be used in a subclass constructor to access inherited members via its super class. One might be tempted to use the super keyword in the constructor to specify initial values of inherited fields. However the super () construct provides a better solution, using superclass constructor to initialize inherited state

How to set the .jar file in classpath through javac command?

Why is compile output i get as below?

public class Super_class { public static void return_Number(){ System.out.println(5); } }
public class Sub_class { public static void return_Number(){ System.out.println(10); } public static void main(String[] args) { System.out.println(Sub_class.return_Number()); System.out.println(Super_class.return_Number()); } }


Output:
---------- Compile ----------
Sub_class.java:8: 'void' type not allowed here
System.out.println(Sub_class.return_Number());
^
Sub_class.java:9: 'void' type not allowed here
System.out.println(Super_class.return_Number());
^
2 errors
Normal Termination
Output completed (0 sec consumed).