Java package - a MUST ???

Question

hi, i'm using jdk1.4 and i'm doing a testing on calling a class without a package
here's the sample
test.java
public class test {
     public test( ) {
          System.out.println("test");
call.java
import test;
public class call {
     public static void main(String args[]) {
          test t = new test();
i compile them in a folder/classpath
after compile the test.java, i then compile the call.java
but i receive this error message:
call.java:1: '.' expected
import test;
do i really hv to package all the source code?

Answer 1

Try to remove the code below from file call.java
import test; // <- remove this line
public class call {
     public static void main(String args[]) {
          test t = new test();
import keyword is only use when you're accessing related classes that are grouped in package, executable jar file.
one class: import <package name>.<class name>;
entire package: import <package name>.*
Example:
If i create 4 related classes as below:-
1. sqrt.java
2. minus.java
3. add.java
4. multiply.java
and I put them into the directory "\math" and then i package. In order for me to use the classes above in my project, say i want to use "sqrt", all i have to do is import the package and class as below:-
import math.sqrt; // <- import one class
import math.*; // <- import entire package
one class: import <package name>.<class name>;
entire package: import <package name>.*
Say when you want to create GUI (eg. a label) in your project, I believe you'll need to import the package java.awt, in order for you to have the object Label in your project.
//The sample code below will return error, since there is no package.awt, because is doesn't recognise the object 'Label'.
public class GUI{
Label lblname = new Label();
For better understanding, try to go to the directory below:-
C:\Program Files\Java\jdk1.5.0\jre\lib
and unzip the file rt.jar, then examine the directory structure within it, you'll notice it's the same as the packages that exist in Java API documentation. If this statement (import java.awt.*;) is valid, then you'll find there is directory '\java\awt' after unzipping the file