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From: Markus Gessner <nospam@nospam.com>
Newsgroups: comp.lang.java.programmer
Subject: Dependency resolution in Java builds
Date: Tue, 08 Feb 2011 23:26:22 +0100
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Hello all!

Having recently started working with Java, coming from C++, I am now
taking part in a Java project, the build of which is managed by Maven.

I frequently run into a very basic situation exemplified by the two
follwing classes, each of which is implemented in its own file:

----------------------------------------------------------------------
public interface Foo
{
  void method1();
}

public class FooImpl implements Foo
{
  void method1() { ; }
}
----------------------------------------------------------------------

After compiling, I make the follwing change, i.e., only change the
interface:

----------------------------------------------------------------------
public interface Foo
{
  void method1();
  void method2();
}

public class FooImpl implements Foo
{
  void method1() { ; }
}
----------------------------------------------------------------------

When building, I see only a recompilation of Foo.java, which
indicates, that only a simple comparison of the respective timestamps
of *.java and *.class files is undertaken. From my C++-work, based on
gcc/make, I am accustomed to a setup, which in the analogous scenario
for C++ detects the dependence of FooImpl on Foo and initiates a
recompilation of FooImpl as well (in this example leading to a compile
time error).

Moreover, from the Java guys i frequently here something like "when in
doubt, clean the project and rebuild".

Although this is a matter of the build tools rather than the language, I
would like to ask the experienced Java developers out here: is this to
be put up with, or are there build mechanisms obviating this, concisely
taking into account the interdependence of classes (like "gcc -M" in a
make-based build system for C++).

Greetings
Markus