11章-练习32

import com.example.demo.typeinfo.pets.Pet;
import com.example.demo.typeinfo.pets.Pets;

import java.util.*;

/**
 * 练习32：按照MultiIterableClass示例，在NonCollectionSequence.java中添加reversed()和randomized()方法，
 * 并让NonCollectionSequence实现Iteraable.然后在foreach语句中展示所有的使用方式
 */
class PetSequence {
    protected Pet[] pets = Pets.createArray(8);
}

public class NonCollectionSequence extends PetSequence implements Iterable<Pet> {
    public Iterator<Pet> iterator() {
        return new Iterator<Pet>() {
            private int index = 0;

            public boolean hasNext() {
                return index < pets.length;
            }

            public Pet next() {
                return pets[index++];
            }

            public void remove() { // Not implemented
                throw new UnsupportedOperationException();
            }
        };
    }

    public Iterable<Pet> reversed() {
        return new Iterable<Pet>() {
            @Override
            public Iterator<Pet> iterator() {
                return new Iterator<Pet>() {
                    int current = pets.length - 1;

                    @Override
                    public boolean hasNext() {
                        return current > -1;
                    }

                    @Override
                    public Pet next() {
                        return pets[current--];
                    }
                };
            }
        };
    }

    public Iterable<Pet> randomized() {
        List<Pet> petList = new ArrayList<Pet>(Arrays.asList(pets));
        Collections.shuffle(petList, new Random(43));

        return new Iterable<Pet>() {
            @Override
            public Iterator<Pet> iterator() {
                return petList.iterator();
            }


        };
    }

    public static void main(String[] args) {
        NonCollectionSequence nc = new NonCollectionSequence();

        for (Pet p : nc) {
            System.out.print(p.id() + ":" + p + " ");
        }
        System.out.println();
        for (Pet p : nc.reversed()) {
            System.out.print(p.id() + ":" + p + " ");
        }
        System.out.println();
        for (Pet p : nc.randomized()) {
            System.out.print(p.id() + ":" + p + " ");
        }

    }

} 
/* Output:
0:Rat 1:Manx 2:Cymric 3:Mutt 4:Pug 5:Cymric 6:Pug 7:Manx 
7:Manx 6:Pug 5:Cymric 4:Pug 3:Mutt 2:Cymric 1:Manx 0:Rat 
7:Manx 6:Pug 0:Rat 4:Pug 3:Mutt 1:Manx 2:Cymric 5:Cymric 
*///:~