Larry Lai

Hi everyone,

I've a homework execrise about that...

1. In what situation would we use an abstract class instead of an interface?

2. In what situation would we use an interface instead of an inheriting from a superclass?

3. When is it better to use an interface rather than an abstract class?

How to think that three kinds of keywords?
Thanks
Larry

Hi everyone,

I'm not sure what swap it is...
Here is an example code:
public int split(Element [] array, int first, int last) { int left= first; int right = last; while (left < right) {//while searches haven't met //Search from the right while (array[first].compare(array[right]) == -1) right--; while ((left < right) && (array[first].compare(array[left]) != -1)) left++; if (left < right) swap(array, left, right); } swap(array, first, right); return left; } // split

If anyone knows, tell me what it's going on...or give one more example for me learning...

Thanks a lot
Larry

Hi guys,
I've asked it before but my question is not very clear so I ask again...
I just want to know how to get started to learn JDBC,
Does anyone have some resource or source code about that ?

Thanks

Larry

Hi everyone,
Does anyone have a basic JDBC resource for study?
The resource is for connection, insert, delete query, update something like that

Thanks
Larry

Hi everyone,

Do you have any resource for learning 'Files and Streams'. I really can't get what the text book is talked.
Thanks...

Larry

Hey Barry,
Thanks a lot
I understand it now.
Larry

Hi everyone,
why this code has a "?"
radius= (circleRadius>=0.0? circleRadius:0.0);
public class Circle extends Point { // inherits from Point protected double radius; // no-argument constructor public Circle() { // implicit call to superclass constructor occurs here setRadius( 0 ); } // constructor public Circle( double circleRadius, int xCoordinate, int yCoordinate ) { // call superclass constructor to set coordinates super( xCoordinate, yCoordinate ); // set radius setRadius( circleRadius ); } // set radius of Circle public void setRadius( double circleRadius ) { radius = ( circleRadius >= 0.0 ? circleRadius : 0.0 ); } // get radius of Circle public double getRadius() { return radius; } // calculate area of Circle public double area() { return Math.PI * radius * radius; } // convert the Circle to a String public String toString() { return "Center = " + "[" + x + ", " + y + "]" + "; Radius = " + radius; } } // end class Circle

Thanks

Larry

Hi everyone,
How're you ?

Do you know how to make the password in the JPasswordField getting the actionperform
then matching that "Javaranch" is the password
then if it's "Javaranch", log on.
Thanks..
Larry

Hi Ron,

the compiler replys about as below:

--------------------Configuration: JDK version 1.31 <Default>--------------------
C:\Documents and Settings\labuser\Desktop\FileInfo.java:11: unreported exception java.io.IOException; must be caught or declared to be thrown
if( !f.exists())f.createNewFile();
^
1 error
Process completed.

Hi Ron,
How're you ?
I mean the complier reply that the f.createFile( )
causes the problem.
I'm not sure what wrong it is...
Larry

Hi everyone,
This is the code as below:
f.createFile( )
the complier show that that is a bug

code:
--------------------------------------------------------------------------------
import java.io.*;public class FileInfo{public static void main(String args[]){// open (or create) fileFile f= new File ("readme.txt");if( !f.exists())f.createNewFile();// display file informationSystem.out.println("File Information");System.out.println("Name:" + f.getName());System.out.println("Path:"+ f.getAbsolutePath());System.out.println("Size:" + f.length()+ "bytes");if(f.canRead())System.out.println("File can read");if(f.canWrite())System.out.println("File can be written to");f.delete();}}
--------------------------------------------------------------------------------

Do you know what wrong it is?
thanks
Larry

Hi everyone,
This is the code as below:
f.createFile( )
the complier show that that is a bug
import java.io.*; public class FileInfo{ public static void main(String args[]){ // open (or create) file File f= new File ("readme.txt"); if( !f.exists())f.createNewFile(); // display file information System.out.println("File Information"); System.out.println("Name:" + f.getName()); System.out.println("Path:"+ f.getAbsolutePath()); System.out.println("Size:" + f.length()+ "bytes"); if(f.canRead()) System.out.println("File can read"); if(f.canWrite()) System.out.println("File can be written to"); f.delete(); } }

Do you know what wrong it is?
thanks
Larry

Hi everyone,
Why should exception-handling techniques not be used for conventional program control?
Thanks

Larry

Hi Dirk,

Thanks a lot what you have done.

Larry

Hi everyone,
How're you doing?
One basic knowledge I'm not familiar with is 'Passing Objects to a Method'
The sample code is as below:
public static void main(String []args){ Sphere ball = new Sphere(10.0, 1.0, 1.0, 1.0); obj.change(ball); //..... }

Sphere change(Sphere s){ s.changeRadius(1.0); return s; }
It's from textbook and it's talked about Passing Object to a Method.
The main point that the author talks about is "copy the reference from obj" then, made it to the s...
I'm not sure what it is? Does anyone know about that ?

Thanks
Larry