Android Open Source - DKO Lazy Cache Iterable

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License

The source code is released under:

GNU Lesser General Public License

Java Source Code

package org.kered.dko;
//  w  w  w.  ja va 2s.c  o  m
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

class LazyCacheIterable<T extends Table> implements Iterable<T> {

  private final Iterable<T> src;
  private Iterator<T> srci = null;
  private final List<T> cache;
  int count = 0;
  boolean completelyLoaded = false;

  public LazyCacheIterable(final Iterable<T> src) {
    this.src = src;
    cache = new ArrayList<T>();
  }

  public LazyCacheIterable(final Iterable<T> src, final int size) {
    this.src = src;
    cache = new ArrayList<T>(size);
  }

  @Override
  public Iterator<T> iterator() {
    if (srci==null) initSourceIterator();
    return new ClosableIterator<T>() {

      int position = 0;

      @Override
      public boolean hasNext() {
        if (position==count && completelyLoaded) return false;
        if (!completelyLoaded) peekNext();
        return position < count;
      }

      @Override
      public T next() {
        return cache.get(position++);
      }

      @Override
      public void remove() {
        throw new UnsupportedOperationException();
      }

      @Override
      public synchronized void close() {
        if (srci instanceof ClosableIterator) ((ClosableIterator)srci).close();
      }

    };
  }

  private synchronized void peekNext() {
    if (srci.hasNext()) {
      cache.add(srci.next());
      ++count;
    } else {
      completelyLoaded = true;
    }
  }

  private synchronized void initSourceIterator() {
    if (srci!=null) return;
    srci = src.iterator();
  }

}

Java Source Code List

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