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Re: package statement in standalone Java class

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On Sat, 07 Apr 2018 08:25:47 -0700, Morten W. Petersen wrote:

> I'm new to Java, and having Java, Maven and different libraries to
> consider if I get an error seems too complex to debug.
> 
Some points to consider:

To a first approximation you should treat Java's 'import' statements as 
the equivalent to C's #include <header.h> preprocessor statements. Just 
as as you can't compile a C program that does anything much without using 
#includes and linking it with the relevant libraries, the only Java 
program you can compile without imports is one that only uses external  
classes from the java.lang group. The big difference it that you never 
need to mention imported classes and packages anywhere else.

I use 'ant' rather than 'maven' - it may be closer to the way make works 
than maven is. The main differences from make are that build.xml is an 
XML document rather than the plaintext with strange ways of using TABs 
and spaces and you find in Makefile and there are built-in XML 
definitions for almost every tool you'll need to build a Java program and 
generate documentation for it.

Don't even think of using 'make' to compile Java. Been there, done that, 
discovered it caiuses problems. While 'make' can be used to build very 
simple programs, the recursive nature of a multi-class Java compile soon 
ties 'make' in knots while 'ant' just gets it done. 

The package names give context to class names, so the custom has grown up 
of using your domain name as the most significant part of a package name 
to guarantee uniqueness, e.g. "com.example.mypackage.MyClass". This 
pretty much guarantees that, although every man and his dog might write 
their own MyClass class and publish it, if you also use this convention 
you'll never end up referencing his MyClass rather than your MyClass. The 
compiler expects this type of structured naming to be reflected in the 
sources its compiling, which is why the source files get names like 
"com/example/mypackage/MyClass.java". So you'd be well-advised to get 
used to working this way as soon as you start writing Java programs that 
contain more than one class.


-- 
Martin    | martin at
Gregorie  | gregorie dot org

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package statement in standalone Java class "Morten W. Petersen" <morphex@gmail.com> - 2018-04-07 04:38 -0700
  Re: package statement in standalone Java class Eric Sosman <esosman@comcast-dot-net.invalid> - 2018-04-07 10:25 -0400
    Re: package statement in standalone Java class "Morten W. Petersen" <morphex@gmail.com> - 2018-04-07 08:25 -0700
      Re: package statement in standalone Java class Martin Gregorie <martin@mydomain.invalid> - 2018-04-07 18:23 +0000
        Re: package statement in standalone Java class Arne Vajhøj <arne@vajhoej.dk> - 2018-04-07 15:58 -0400
          Re: package statement in standalone Java class Martin Gregorie <martin@mydomain.invalid> - 2018-04-07 20:28 +0000
            Re: package statement in standalone Java class Arne Vajhøj <arne@vajhoej.dk> - 2018-04-07 16:32 -0400
              Re: package statement in standalone Java class Martin Gregorie <martin@mydomain.invalid> - 2018-04-07 21:35 +0000
              Re: package statement in standalone Java class Eric Douglas <e.d.programmer@gmail.com> - 2018-04-09 04:57 -0700
                Re: package statement in standalone Java class Arne Vajhøj <arne@vajhoej.dk> - 2018-04-09 18:01 -0400
                Re: package statement in standalone Java class Arne Vajhøj <arne@vajhoej.dk> - 2018-04-09 18:07 -0400
                Re: package statement in standalone Java class Arne Vajhøj <arne@vajhoej.dk> - 2018-04-09 19:34 -0400
                Re: package statement in standalone Java class "Morten W. Petersen" <morphex@gmail.com> - 2018-04-10 16:28 -0700
        Re: package statement in standalone Java class "Morten W. Petersen" <morphex@gmail.com> - 2018-04-07 16:14 -0700

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