[J17] Add intermodule class loading example description

Author: temikfart

img/Java 17. Auto Loading (dependent and dependency).jpg

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+## Java 17. Auto Loading (dependent and dependency)
+---
+**Task:** load the classes of an application consisting of two modules (the modules are linked via `module-info.java`) using a custom class loader (`CustomClassLoader`).
+
+### Solution
+---
+Modules (declared via `module-info.java`):
+- `manual.fewmodules.together.dependent`:
+    - [`Main`](dependent/src/ru/ispras/j17/manual/fewmodules/together/dependent/Main.java) - a class containing a `main` method creating an instance of the `Cat` class and calling the `Cat::talk` method;
+    - [`CustomClassLoader`](dependent/src/ru/ispras/j17/manual/fewmodules/together/dependent/CustomClassLoader.java) - a class that is an implementation of a custom class loader;
+- `manual.fewmodules.together.dependency`:
+    - [`Cat`](dependency/src/ru/ispras/j17/manual/fewmodules/together/dependency/Cat.java) - loadable class with the `talk` method, which prints the string *"Meow"* to `stdout`.
+
+To change the system loader to a custom `CustomClassLoader` in [documentation of the `ClassLoader.getSystemClassLoader()` method](https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/ClassLoader.html#getSystemClassLoader()) it is written that for this it is necessary for the JVM to pass the name of the new *system class loader* through the argument `java.system.class.loader`, and also to define a public constructor with a parameter of type `ClassLoader`, which will be passed as `AppClassLoader` when created.
+
+### Run
+---
+Using `modulepath`:
+
+```shell
+java17 -Djava.system.class.loader=ru.ispras.j17.auto.fewmodules.together.dependent.CustomClassLoader \
+-p dependent-1.0.jar:dependency-1.0.jar -m auto.fewmodules.together.dependent
+```
+
+Output:
+
+```shell
+Main Class Module is module auto.fewmodules.together.dependent
+Cat Class Module is module auto.fewmodules.together.dependency
+System ClassLoader is ru.ispras.j17.auto.fewmodules.together.dependent.CustomClassLoader@5a07e868
+Main Class ClassLoader is jdk.internal.loader.ClassLoaders$AppClassLoader@42a57993
+Cat Class ClassLoader is jdk.internal.loader.ClassLoaders$AppClassLoader@42a57993
+Meow
+```
+
+### Explanation
+---
+![Java 17. Auto Loading (dependent and dependency).jpg](../../../../img/Java%2017.%20Auto%20Loading%20(dependent%20and%20dependency).jpg)
+
+- Regarding [Java 17. Auto Loading (Java 17 style)](../../one-module/java17style) the only difference is that there are two 
+  modules that 
+  are 
+  loaded using `AppClassLoader`.
+
+### Notes
+---
+*Same as in [Java 17. Auto Loading (Java 17 style)](../../one-module/java17style)*.
+
+- In `module-info.java` of the `dependency` module you need to export the package with the `Cat` class, and in `module-info.java` of the `dependent` module, specify the dependency on the `dependency` module and export the custom class loader `CustomClassLoader`:
+
+```java
+// dependency/src/module-info.java
+module auto.fewmodules.together.dependency {
+    exports ru.ispras.j17.auto.fewmodules.together.dependency;
+}
+```
+
+```java
+// dependent/src/module-info.java
+module.auto.fewmodules.together.dependent {
+    requires auto.fewmodules.together.dependency:
+
+    exports ru.ispras.j17.auto.fewmodules.together.dependent to java.base;
+}
+```