RxJavaFromCleanupIterableSolution.java

import rx.Observable;
import rx.functions.Action0;
import rx.functions.Action1;
import rx.functions.Func0;
import rx.functions.Func1;

/**
 * @author stw
 *
 */
public class RXTest {

  public static void main(String[] args) {

    Observable<FancyObject> source = Observable.using(new Func0<ComplicatedObject>() {
      @Override
      public ComplicatedObject call() {
        return new ComplicatedObject();
      }
    }, new Func1<ComplicatedObject, Observable<FancyObject>>() {

      @Override
      public Observable<FancyObject> call(ComplicatedObject co) {
        return Observable.from(co);
      }
    },
        
        new Action1<ComplicatedObject>() {

          @Override
          public void call(ComplicatedObject co) {
            co.tearDown();
          }
        });

    source.take(3).subscribe(new Action1<FancyObject>() {

      public void call(FancyObject item) {
        System.out.println(item.getName());
      }
    }, new Action1<Throwable>() {

      public void call(Throwable error) {
        System.out.println("Error encountered: " + error.getMessage());
      }
    }, new Action0() {

      public void call() {
        System.out.println("Sequence complete");
      }
    }
    );
  }
}

/* --------------- */
import java.util.Date;
import java.util.UUID;

/**
 * @author stw
 *
 */
public class FancyObject  {
  private String name = UUID.randomUUID().toString();
  private Date created = new Date();
  public String getName() {
    return this.name;
  }
  public void setName(String name) {
    this.name = name;
  }
  public Date getCreated() {
    return this.created;
  }
  public void setCreated(Date created) {
    this.created = created;
  }
}

/* --------------- */
import java.util.Iterator;

public class FancyIterator implements Iterator<FancyObject> {
  
  private final ComplicatedObject theObject;
  private int fancyCount = 0;
  
  
  public FancyIterator(ComplicatedObject co) {
    this.theObject = co;
  }

  public boolean hasNext() {
    return this.theObject.hasObject(this.fancyCount);
   }


   public FancyObject next() {
     FancyObject result = this.theObject.getOne(this.fancyCount);
     this.fancyCount++;  
     return result;
   }
  
}


/* --------------- */

import java.util.Iterator;
import java.util.Vector;

/**
 * @author stw
 *
 */
public class ComplicatedObject implements Iterable<FancyObject> {
  
  private boolean isInitialized = false;
 
  Vector<FancyObject> allOfThem = new Vector<FancyObject>();


  public Iterator<FancyObject> iterator() {
   return new FancyIterator(this);
  }
  
  public boolean hasObject(int whichone) {
    if (!this.isInitialized) {
      this.setupAccesstoFancyObject(); 
    }
    return (whichone < this.allOfThem.size());
  }
  public FancyObject getOne(int whichone) {
      if (!this.isInitialized) {
        this.setupAccesstoFancyObject();
      }
      if (whichone < this.allOfThem.size()) {
        return this.allOfThem.get(whichone);
      }
      // If we ask bejond...
      this.isInitialized = false;
      this.tearDown();
      return null;
  }
 
  private void setupAccesstoFancyObject() {
    System.out.println("Initializing fancy objects");
    for (int i = 0; i < 20; i++) {
      this.allOfThem.addElement(new FancyObject());
    }
    this.isInitialized = true;
  }

  public void tearDown() {
    System.out.println("I'm doing proper cleanup here");
   
  }

}