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Thread: Taking an element out of an array

  1. #1
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    Default Taking an element out of an array

    I'm trying to take an animal element of an array for filtering but I'm having some problems. I need to take the element i need out of the array. Then I need to find out whether the animal is the type I need. Finally I need to add the animal object to the array. I have to seperate arrays of displayed animals and all the animals but I'm just having trouble figuring out how to do the above. Any advice is greatly appreciated. Here's what I have so far:

     
     
           public void filterDogs()
          {
     
     
             Iterator i = animals.iterator();
     
             while(i.hasNext()) 
             { 
                Animal a = (Animal)i.next(); 
                if(a instanceof Dog)
                  Dog += displayedAnimals.add(a); 
             }
          }

    And the entire code:
       import javax.swing.*;  
       import java.util.ArrayList;
       import java.util.*;
       import java.util.Collections;
       import javax.swing.Timer;
     
     
        public class AnimalListDisplay extends JList
       {
          ArrayList<Animal> animals;
          ArrayList<Animal> displayedAnimals;
     
          boolean specialNeedsOnly = false;
          boolean birdsOn = false;
          boolean dogsOn = false;
          boolean catsOn = false;
     
     
           public AnimalListDisplay(ArrayList<Animal> allAnimals)
          {
     
             animals = allAnimals;
             displayedAnimals = animals;
          }
           public void addAnimal(Animal animal)
          {
             animals.add(animal);
     
             setListData(animals.toArray());
     
          }
           public void sortAge()
          {
     
             AgeCompare a1 = new AgeCompare();
             Collections.sort(displayedAnimals, a1);
             setListData(displayedAnimals.toArray());
          }
     
     
           public void sortSize()
          {
     
             Collections.sort(displayedAnimals);
             setListData(displayedAnimals.toArray());
          }
     
     
           public void filterSpecialNeeds()
          {
     
             if(specialNeedsOnly == false)
             {
                displayedAnimals = new ArrayList<Animal>();
     
                Iterator i = animals.iterator();
     
                while(i.hasNext())
                {
                   Animal a = (Animal)i.next();
                   if(a.getNeeds())
                      displayedAnimals.add(a);
                }
                setListData(displayedAnimals.toArray());
                specialNeedsOnly = true;
             }
     
             else if(specialNeedsOnly == true)
             {
     
                setListData(animals.toArray());
                specialNeedsOnly = false;
     
             }
          }
     
          // public void addAnimal(Animal pet){
            // displayedAnimals.add(pet);
            // animals.add(pet);
     
     
     
     
           public void filterDogs()
          {
     
     
             Iterator i = animals.iterator();
     
             while(i.hasNext()) 
             { 
                Animal a = (Animal)i.next(); 
                if(a instanceof Dog)
                   displayedAnimals.add(a); 
             }
          }
           public void filterCats()
          {
             if(catsOn == false)
             {
                displayedAnimals = new ArrayList<Animal>();
     
                Iterator i = animals.iterator();
     
                while(i.hasNext())
                {
                   Animal a = (Animal)i.next();
                   if(a.getNeeds())
                      displayedAnimals.add(a);
                }
                setListData(displayedAnimals.toArray());
                catsOn = true;
             }
     
             else if(catsOn == true)
             {
     
                setListData(animals.toArray());
                catsOn = false;
             }
          }
           public void filterBirds()
          {
             if(birdsOn == false)
             {
                displayedAnimals = new ArrayList<Animal>();
     
                Iterator i = animals.iterator();
     
                while(i.hasNext())
                {
                   Animal a = (Animal)i.next();
                   if(a.getNeeds())
                      displayedAnimals.add(a);
                }
                setListData(displayedAnimals.toArray());
                birdsOn = true;
             }
     
             else if(birdsOn == true)
             {
     
                setListData(animals.toArray());
                birdsOn = false;
     
             }
     
     
          }
       }


  2. #2
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    Default Re: Taking an element out of an array

    Your thinking way to difficult dude.

    public abstract class Animals
    {
    	public static final Integer CATS = 0;
    	public static final Integer DOGS = 1;
    	public static final Integer BIRDS = 2;
    	protected Hashtable<Animal> animals = new Hashtable<Animal>(); //protected!!!
     
    	public abstract Hashtable<Animal> collect(int specieType);
    	public abstract void add(Animal a);
    	public abstract Animal get(int id);
    	public abstract void edit(Animal a);
    	public abstract boolean remove(Animal a);
    }
     
    public class AnimalCollection extends Animals
    {
    	private Hashtable<Animal> collection = new Hashtable<Animal>();
     
    	public Hashtable<Animal> collect(int specieType)
    	{
    		String specie;
    		switch(specieType)
    		{
    			case 0:
    				specie = "Cat";
    			break;
    			case 1:
    				specie = "Dog";
    			break;
    			case 2:
    				specie = "Bird";
    			break;
    			default:
    				throw new Exception("Unknown type.");
    		}
     
    		Hashtable<Animal> col = new hashtable<Animal>();
    		for(Animal a : super.animals)
    		{
    			if(a instanceof specie)
    			{
    				col.put(a.hashCode(), a);
    			}
    		}
    		this.collection = col; //if you want to have the same collection some time later, you load this and dont call the method again(performance)
    		return col;
    	}
     
    	@override
    	public void add(Animal a) {}
     
    	@override
    	public Animal get(int id) {}
     
    	@override
    	public void edit(Animal a) {}
     
    	@override
    	public boolean remove(Animal a) {}
    }
     
    Call: 
    AnimalCollection aC = new AnimalCollection();
    Hashtable dogsCollection = aC.collect(Animals.DOGS);
    I made this with notepad++ so there may be some syntax errors.
    Last edited by Bryan; May 3rd, 2010 at 07:00 AM.

  3. #3
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    Default Re: Taking an element out of an array

    Please use [highlight=Java] code [/highlight] tags when posting your code.
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  4. #4
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    Default Re: Taking an element out of an array

    Quote Originally Posted by Bryan View Post
    public abstract class Animals
    {
    	public static final Integer CATS = 0;
    	public static final Integer DOGS = 1;
    	public static final Integer BIRDS = 2;
    	protected Hashtable<Animal> animals = new Hashtable<Animal>(); //protected!!!
     
    	public abstract Hashtable<Animal> collect(int specieType);
    	public abstract void add(Animal a);
    	public abstract Animal get(int id);
    	public abstract void edit(Animal a);
    	public abstract boolean remove(Animal a);
    }
     
    public class AnimalCollection extends Animals
    {
    	private Hashtable<Animal> collection = new Hashtable<Animal>();
     
    	public Hashtable<Animal> collect(int specieType)
    	{
    		String specie;
    		switch(specieType)
    		{
    			case 0:
    				specie = "Cat";
    			break;
    			case 1:
    				specie = "Dog";
    			break;
    			case 2:
    				specie = "Bird";
    			break;
    			default:
    				throw new Exception("Unknown type.");
    		}
     
    		Hashtable<Animal> col = new hashtable<Animal>();
    		for(Animal a : super.animals)
    		{
    			if(a instanceof specie)
    			{
    				col.put(a.hashCode(), a);
    			}
    		}
    		this.collection = col; //if you want to have the same collection some time later, you load this and dont call the method again(performance)
    		return col;
    	}
     
    	@override
    	public void add(Animal a) {}
     
    	@override
    	public Animal get(int id) {}
     
    	@override
    	public void edit(Animal a) {}
     
    	@override
    	public boolean remove(Animal a) {}
    }
     
    Call: 
    AnimalCollection aC = new AnimalCollection();
    Hashtable dogsCollection = aC.collect(Animals.DOGS);
    I made this with notepad++ so there may be some syntax errors.
    Hmm, that needs a bit more work...
    Don't forget that a Hashtable is a keyed collection, so should be declared with two generic type arguments - but a Hashtable won't work here if you want more than one instance of each species in the collection - Hashtable keys are unique.
    You could profitably replace the Integer 'specieType' with an enum.
    It would simplify things if an Animal knew its specieType - which it should.
    Should AnimalCollection really extend Animals, or does this complicate things?
    There seems little point in having a Hashtable of a single animal species, ArrayList would be more appropriate (especially if an Animal knows its Species)?

    If all that's needed is to extract a particular species from a mixed collection, wouldn't something like this be simpler:
    import java.util.ArrayList;
    import java.util.List;
     
    class AnimalFilter
    {
        public static void main(String[] args) {
            List<Animal> animals = new ArrayList<Animal>();
            animals.add(new Dog(..));
            animals.add(new Cat(..));
            animals.add(new Bird(..));
            animals.add(new Dog(..));
            animals.add(new Bird(..));
     
            AnimalFilter filter = new AnimalFilter();
            List<Animal> dogsCollection = filter.collect(animals, Animal.Species.DOGS);
            ... // do something with Dogs
        }
     
    	public List<Animal> collect(List<Animal> animals, Animal.Species species)
    	{
    		List<Animal> selectedAnimals = new ArrayList<Animal>();
    		for(Animal animal : animals)
    		{
    			if(animal.isSpecies(species)) {
    				selectedAnimals.add(animal);
    			}
    		}
    		return selectedAnimals;
    	}   
    }
     
    abstract class Animal {
        public enum Species { CATS, DOGS, BIRDS }
     
        protected Species species;
     
        public Species getSpecies() {
            return species;
        }
        public boolean isSpecies(Species s) {
            return species == s;
        }
    }
     
    class Dog extends Animal { ... }
    class Cat extends Animal { ... }
    class Bird extends Animal { ... }
    If an explicit Species type id isn't needed, you could even get rid of the Species enum and just use the Animal class type:
    class AnimalFilter
    {
        public static void main(String[] args) {
            List<Animal> animals = new ArrayList<Animal>();
            animals.add(new Dog(..));
            animals.add(new Cat(..));
            animals.add(new Bird(..));
            animals.add(new Dog(..));
            animals.add(new Bird(..));
     
            AnimalFilter filter = new AnimalFilter();
            List<Animal> dogsCollection = filter.collect(animals, Dog.class);
            ... // do something with Dogs
        }
     
    	public List<Animal> collect(List<Animal> animals, Class speciesClass)
    	{
    		List<Animal> selectedAnimals = new ArrayList<Animal>();
    		for(Animal animal : animals)
    		{
    			if(animal.getClass().equals(speciesClass)) {
    				selectedAnimals.add(animal);
    			}
    		}
    		return selectedAnimals;
    	}
    }
     
    abstract class Animal { ... }
    class Dog extends Animal { ... }
    class Cat extends Animal { ... }
    class Bird extends Animal { ... }
    YMMV.

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