	CS 596 Java Programming Fall Semester, 1998 Using New Features
	To Lecture Notes Index © 1998, All Rights Reserved, SDSU & Roger Whitney San Diego State University -- This page last updated 10-Oct-98

Contents of Doc 12, Using New Features

Reference

Personal experience


S-oct7 6mins, Q-oct8 2mins Doc 12, Using New Features Slide # 2

Using Language Features for the First Time

Rule 1

In a separate program, test the language feature using the smallest possible program. Do this before using the feature in a "real" program.

Motivation

Small programs are fast to write, easy to understand, easy to debug

Example - Packages
In file: ~masc01146/whitney/Sample.java:

package whitney;
public class Sample {
   public void print() {
      System.out.println( "In foo");
   }
}

In file: ~masc01146/Test.java


import whitney.Sample;
class Test {
   public static void main( String[] args ){
   Sample aTest = new Sample();
   aTest.print();
   }

Set classpath:

setenv CLASSPATH  '.:/home/ma/cs596/masc01146'
Doc 12, Using New Features Slide # 3

Using Language Features for the First Time

Rule 2

Actual use Rule 1. It will save you time.

Rule 3

First get something working, then try one variation at a time.


Doc 12, Using New Features Slide # 4

Using Tech Support (or Instructors, TAs)
Tech support people (& instructors, TAs) are not mind readers nor do they have any supernatural powers.

You need to provide them with your problem and the relevant information in short message

Example Message 1 "I am having problems with packages. I followed your example. It does not work for me. My classes worked before I added the packages. What am I doing wrong?


Doc 12, Using New Features Slide # 5

Example 2 I am having problems with packages. In file: ~masc01146/whitney/Sample.java I have

package whitney;
class Sample {
   public void print() {
      System.out.println( "In foo");
   }
}

In file: ~masc01146/ whitney/Test.java


import whitney.*;
class Test {
   public static void main( String[] args ){
   Sample aTest = new Sample();
   aTest.print();
   }

I set classpath by:

setenv CLASSPATH  '.'

I then compile Test using:

javac Test.java

I then get the following error message:

Can't access class whitney.Sample. Class or interface must be public, in same package, or an accessible member class.
classNotes.java line 5    Sample aTest = new Sample();

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