registeredpetfactories15.java

JAVA编程思想第四版英文原版习题答案. pdf原版的

// typeinfo/RegisteredPetFactories15.java
// TIJ4 Chapter Typeinfo, Exercise 15, page 586
/* Implement a new PetCreator using Registered Factories, and modify the Pets
* Facade so that it uses this one instead of the other two. Ensure that the 
* rest of the examples that use Pets.java still work correctly.
*/
import java.util.*;
import typeinfo.pets.*;

public class RegisteredPetFactories15 {
	public static void main(String[] args) {
		for(int i = 0; i < 10; i++)
			System.out.println(PetFactory.createRandom());
	}
}

/* Solution includes rewrite of base-class, Individual15, to extend PetFactory
* and changes to methods in Pets and PetCreator:
* // typeinfo/pets/Individual15.java
* // for use in solution to Ex 15, page 586
* package typeinfo.pets;
* import typeinfo.factory.*;
* import java.util.*;
*
* class PetFactory {
*	public String toString() {
*		return getClass().getSimpleName();
*	}
*	static List<Factory<? extends Pet>> petFactories = 
*		new ArrayList<Factory<? extends Pet>>();
*	static {
*		petFactories.add(new Pet.Factory());
*		petFactories.add(new Cat.Factory());
*		petFactories.add(new Cymric.Factory());
*		petFactories.add(new Dog.Factory());
*		petFactories.add(new EgyptianMau.Factory());
*		petFactories.add(new Gerbil.Factory());
*		petFactories.add(new Hamster.Factory());
*		petFactories.add(new Manx.Factory());
*		petFactories.add(new Mouse.Factory());
*		petFactories.add(new Mutt.Factory());
*		petFactories.add(new Pug.Factory());
*		petFactories.add(new Rat.Factory());
*		petFactories.add(new Rodent.Factory());
*	}
*	private static Random rand = new Random();
*	public static Pet createRandom() {
*		int n = rand.nextInt(petFactories.size());
*		return petFactories.get(n).create();
*	} 
* }
*
* public class Individual15 extends PetFactory implements Comparable<Individual15> {
*	private static long counter = 0;
*	private final long id = counter++;
*	private String name;
*	public Individual15(String name) { this.name = name; }
*	// 'name' is optional:
*	public Individual15() {}
*	public String toString() {
*		return getClass().getSimpleName() + 
*			(name == null ? "" : " " + name);
*	}
*	public long id() { return id; }
*	public boolean equals(Object o) {
*		return o instanceof Individual15 &&
*			id == ((Individual15)o).id;
*	}
*	public int hashCode() {
*		int result = 17;
*		if(name != null)
*			result = 37 * result + name.hashCode();
*		result = 37 * result + (int)id;
*		return result;
*	}
*	public int compareTo(Individual15 arg) {
*		// Compare by class name first:
*		String first = getClass().getSimpleName();
*		String argFirst = arg.getClass().getSimpleName();
*		int firstCompare = first.compareTo(argFirst);
*		if(firstCompare != 0)
*		return firstCompare;
*		if(name != null && arg.name != null) {
*			int secondCompare = name.compareTo(arg.name);
*			if(secondCompare != 0)
*				return secondCompare;
*		}
*		return (arg.id < id ? -1 : (arg.id == id ? 0 : 1));
*	}
* }
*
* // typeinfo/pets/Pets.java
* // Facade to produce a default PetCreator.
* package typeinfo.pets;
* import java.util.*;
*
* public class Pets {
*	public static final PetCreator creator = 
*		new LiteralPetCreator();
*	public static Pet randomPet() { // new method version
*		return PetFactory.createRandom();
*	}
*	// older method version:
*	// public static Pet randomPet() {
*	//	return creator.randomPet();
*	// }	
*	//	
*	public static Pet[] createArray(int size) {
*		return creator.createArray(size);
*	}
*	public static ArrayList<Pet> arrayList(int size) {
*		return creator.arrayList(size);
*	}
* }
*
* // typeinfo/pets/PetCreator.java
* // Creates random sequence of pets
* package typeinfo.pets;
* import java.util.*;
* 
* public abstract class PetCreator {
*	private Random rand = new Random();
*	// The List of the different types of Pet to create:
*	public abstract List<Class<? extends Pet>> types();
*
*	public Pet randomPet() { // newer method, using PetFactory
*		return PetFactory.createRandom();
*	}
*
*	// older, first method:
*	// public Pet randomPet() { // Create one random Pet
*	//	int n = rand.nextInt(types().size());
*	//	try {
*	//		return types().get(n).newInstance();
*	//	} catch(InstantiationException e) {
*	//		throw new RuntimeException(e);
*	//	} catch(IllegalAccessException e) {
*	//		throw new RuntimeException();
*	//	}
*	// }
*	
*	public Pet[] createArray(int size) {
*		Pet[] result = new Pet[size];
*		for(int i = 0; i < size; i++)
*			result[i] = randomPet();
*		return result;
*	}
*	public ArrayList<Pet> arrayList(int size) {
*		ArrayList<Pet> result = new ArrayList<Pet>();
*		Collections.addAll(result, createArray(size));
*		return result;
*	}
* } 
*/