EnumeratorIterator.java

package jetbrains.mps.internal.collections.runtime.impl;

/*Generated by MPS */

import jetbrains.mps.internal.collections.runtime.IEnumerator;
import java.util.NoSuchElementException;
import jetbrains.mps.internal.collections.runtime.Sequence;

public class EnumeratorIterator<T> implements IEnumerator.Iterator<T> {
  private final java.util.Iterator<T> delegate;
  private T current;
  private boolean hasCurrent = false;
  private EnumeratorIterator(java.util.Iterator<T> iterator) {
    if (iterator == null) {
      throw new NullPointerException();
    }
    delegate = iterator;
  }
  @Override
  public boolean hasNext() {
    return delegate.hasNext();
  }
  @Override
  public T next() {
    primMoveNext();
    return primCurrent();
  }
  @Override
  public void remove() {
    delegate.remove();
  }
  @Override
  public T current() {
    return primCurrent();
  }
  @Override
  public boolean moveNext() {
    return primMoveNext();
  }
  private T primCurrent() {
    if (!(hasCurrent)) {
      throw new NoSuchElementException();
    }
    return current;
  }
  private boolean primMoveNext() {
    hasCurrent = delegate.hasNext();
    current = (hasCurrent ? delegate.next() : null);
    return hasCurrent;
  }
  public static <U> IEnumerator.Iterator<U> fromIterator(java.util.Iterator<U> itr) {
    if (Sequence.IGNORE_NULL_VALUES) {
      if (itr == null) {
        return EnumeratorIterator.Empty.instance();
      }
    }
    if (itr instanceof IEnumerator.Iterator) {
      return (IEnumerator.Iterator<U>) itr;
    }
    return new EnumeratorIterator<U>(itr);
  }
  protected static class Empty<U> implements IEnumerator.Iterator<U> {
    private static EnumeratorIterator.Empty<Object> INSTANCE = new EnumeratorIterator.Empty<Object>();
    protected Empty() {
    }
    @Override
    public U current() {
      throw new NoSuchElementException();
    }
    @Override
    public boolean hasNext() {
      return false;
    }
    @Override
    public boolean moveNext() {
      return false;
    }
    @Override
    public U next() {
      throw new NoSuchElementException();
    }
    @Override
    public void remove() {
      throw new UnsupportedOperationException();
    }
    @SuppressWarnings(value = "unchecked")
    public static <V> EnumeratorIterator.Empty<V> instance() {
      return (EnumeratorIterator.Empty<V>) INSTANCE;
    }
  }
}