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Old 07-18-2004, 01:44 AM   #1
lmellen
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Registered: Jan 2004
Location: Fairport, NY
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A very basic newbie question on Java


I've purchased "The Java Tutorial, Third Edition" . It was written for the j2sdk1.3 compiler. Iv'e downloaded j2sdk1.4_05 into FC2. Will the newer compiler not always work with the examples in the book? I'm working on a example called "CreateObjectDemo" that
creates a rectangle. The code:

Point origin_one = new Point(23, 94);
Rectangle rect_one = new Rectangle(origin_one, 100, 200);
Rectangle rect_two = new Rectangle(50, 100);

When I run javac the compiler gives me an error message that states:
"cannot resolve symbol"
It points to each Point and each Rectangle for 6 errors.
Here's the whole program:

public class CreateObjectDemo {

public static void main(String[] args) {

// Declare and create a point object and two rectangle objects

Point origin_one = new Point(23, 94);
Rectangle rect_one = new Rectangle(origin_one, 100, 200);
Rectangle rect_two = new Rectangle(50, 100);

// Display rect_one's width, height, and area

System.out.println("Width of rect_one: " + rect_one.width);
System.out.println("Height of rect_one: " + rect_one.height);
System.out.println("Area of rect_one: " + rect_one.area());

// Set rect_two's position

rect_two.origin = origin_one;

// Display rect_two's position

System.out.println("X Position of rect_two: " + rect_two.origin.x);
System.out.println("Y Position of rect_two: " + rect_two.origin.y);

// Move rect_two and display its new position

rect_two.move(40, 72);

System.out.println("X Position of rect_two: " + rect_two.origin.x);
System.out.println("Y Position of rect_two: " + rect_two.origin.y);

}
}

I guess I just need to know if I should use j2sdk1.3. It's on the disk that came with the book.
The compilers are not backward compatible? Sorry for the dumb newbie problem.
Thanks in advance -- Larry
 
Old 07-18-2004, 03:12 AM   #2
rgiggs
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Location: berkeley, ca
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i believe java is backwards compatible, so you should be OK. at least, right now, your problem is not compatibility; it seems to be something simpler:
does the example show you how to write the Point and Rectangle classes, too? if so, put the java files for those 2 classes in the same directory where the java file for your CreateObjectDemo class is. otherwise, they are library classes, and from the jdk1.4.2 api at http://java.sun.com/j2se/1.4.2/docs/api/index.html, you need to add the following lines to the beginning of the CreateObjectDemo file.
Code:
import java.awt.Point;
import java.awt.Rectangle;

Last edited by rgiggs; 07-18-2004 at 03:28 AM.
 
Old 07-18-2004, 11:51 AM   #3
lmellen
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Many thanks rgiggs, You were right. I didn't have to import , I had to make a Point and a Rectangle class. The book is a little confusing.
One other quick question if I may? I notice your'e using slack 10? I burned a copy the other day. Are the alsa
utils, etc, etc now available? I was browsing somewhere and they were complaining that everything was still for 9.1
Thanks for the reply -- Larry
 
Old 07-18-2004, 12:09 PM   #4
rgiggs
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Quote:
Originally posted by lmellen
Are the alsa utils, etc, etc now available? I was browsing somewhere and they were complaining that everything was still for 9.1.
ummm... if you mean alsaconf, alsamixer... then yes. i din't use 9.1 much at all, so i don't know whether the alsa utils in 10 are newer versions. still, a few sound programs shouldn't prevent you from using a great distro.
 
Old 07-19-2004, 12:54 PM   #5
jpostma
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Eclipse is a good IDE for Java. You can easily determine and correct errors and exceptions.
 
Old 07-19-2004, 03:59 PM   #6
Earth
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Quote:
Originally posted by jpostma
Eclipse is a good IDE for Java. You can easily determine and correct errors and exceptions.
It's also not the easiest IDE to dive into for learning java immediately.
 
  


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