#107 Double Dispatch example JavaDoc

This commit is contained in:
Ilkka Seppala 2015-08-18 22:32:13 +03:00
parent 57e702db4f
commit f2db01e546
2 changed files with 13 additions and 4 deletions

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@ -8,23 +8,27 @@ import java.util.List;
* When a message with a parameter is sent to an object, the resultant behaviour is defined by the
* implementation of that method in the receiver. Sometimes the behaviour must also be determined
* by the type of the parameter.
*
* <p>
* One way to implement this would be to create multiple instanceof-checks for the methods parameter.
* However, this creates a maintenance issue. When new types are added we would also need to change
* the method's implementation and add a new instanceof-check. This violates the single responsibility
* principle - a class should have only one reason to change.
*
* <p>
* Instead of the instanceof-checks a better way is to make another virtual call on the parameter
* object. This way new functionality can be easily added without the need to modify existing
* implementation (open-closed principle).
*
* In this example we have hierarchy of objects (GameObject) that can collide to each other. Each
* <p>
* In this example we have hierarchy of objects ({@link GameObject}) that can collide to each other. Each
* object has its own coordinates which are checked against the other objects' coordinates. If
* there is an overlap, then the objects collide utilizing the Double Dispatch pattern.
*
*/
public class App {
/**
* Program entry point
* @param args command line args
*/
public static void main( String[] args ) {
// initialize game objects and print their status
List<GameObject> objects = new ArrayList<>();

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@ -4,6 +4,11 @@ import org.junit.Test;
import com.iluwatar.doubledispatch.App;
/**
*
* Application test
*
*/
public class AppTest {
@Test