#ctci

AnimalShelter.java

import java.util.Date;
public class Animal{
    String type;
    Date arrived;
}

public class Dog extends Animal{
    String name;
    public Dog(String name){
        super();
        this.name = name;
        type = "Dog";
    }
}

public class Cat extends Animal{
    String name;
    public Cat(String name){
        super();
        this.name = name;
        type = "Cat";
    }
}

import java.util.Queue;
import java.util.LinkedList;
import java.util.Date;
public class AnimalShelter{
    private Queue<Cat> cats;
    private Queue<Dog> dogs;
    
    public AnimalShelter(){
        cats = new LinkedList<Cat>();
        dogs = new LinkedList<Dog>();
    }
    
    public void enqueue(Animal animal) throws Exception{
        boolean isCat = animal.type.equals("Cat");
        boolean isDog = animal.type.equals("Dog");
        if(!isCat && !isDog)
            throw new Exception("Unknow type of animal!");
        
        animal.arrived = new Date();
        if(isCat) cats.offer((Cat) animal);
        else dogs.offer((Dog) animal);
    }
    
    public Animal dequeueAny() throws Exception{
        boolean noCat = cats.isEmpty();
        boolean noDog = dogs.isEmpty();
        
        if(noCat && noDog) throw new Exception("There are no more animals!");
        
        if(noDog) return cats.poll();
        if(noCat) return dogs.poll();
        return cats.peek().arrived.compareTo(dogs.peek().arrived) < 0 ? cats.poll() : dogs.poll(); 
    }
    
    public Cat dequeueCat() throws Exception{
        boolean noCat = cats.isEmpty();
        if(noCat) throw new Exception("There are no more cats!");
        return cats.poll();
    }
    
    public Dog dequeueDog() throws Exception{
        boolean noDog = dogs.isEmpty();
        if(noDog) throw new Exception("There are no more dogs!");
        return dogs.poll();
    }
}