Java Code Examples for org.apache.commons.collections.iterators.EmptyIterator#INSTANCE

@Override
protected Iterator<E> flatMap(final Traverser.Admin<Element> traverser) {
    for (String appliesToLabel : appliesToLabels) {
        String label = SqlgUtil.originalLabel(appliesToLabel);
        Object o = traverser.path().get(label);
        if (o instanceof List) {
            List<SqlgElement> objects = (List) o;
            SqlgElement last = objects.get(objects.size() - 1);
            if (this.returnType.equals(PropertyType.VALUE)) {
                return last.values(this.propertyKeys);
            } else {
                return (Iterator)last.properties(this.propertyKeys);
            }
        } else {
            SqlgElement sqlgElement = traverser.path().get(label);
            if (this.returnType.equals(PropertyType.VALUE)) {
                return sqlgElement.values(this.propertyKeys);
            } else {
                return (Iterator) sqlgElement.properties(this.propertyKeys);
            }
        }
    }
    return EmptyIterator.INSTANCE;
}
 

public Iterator iterator() {
    if (parent.delegateMap != null) {
        return parent.delegateMap.entrySet().iterator();
    }
    if (parent.size() == 0) {
        return EmptyIterator.INSTANCE;
    }
    return new EntrySetIterator(parent);
}
 

public Iterator iterator() {
    if (parent.delegateMap != null) {
        return parent.delegateMap.keySet().iterator();
    }
    if (parent.size() == 0) {
        return EmptyIterator.INSTANCE;
    }
    return new KeySetIterator(parent);
}
 

public Iterator iterator() {
    if (parent.delegateMap != null) {
        return parent.delegateMap.values().iterator();
    }
    if (parent.size() == 0) {
        return EmptyIterator.INSTANCE;
    }
    return new ValuesIterator(parent);
}
 

/**
 * Creates an entry set iterator.
 * Subclasses can override this to return iterators with different properties.
 * 
 * @return the entrySet iterator
 */
protected Iterator createEntrySetIterator() {
    if (size() == 0) {
        return EmptyIterator.INSTANCE;
    }
    return new EntrySetIterator(this);
}
 

/**
 * Creates a key set iterator.
 * Subclasses can override this to return iterators with different properties.
 * 
 * @return the keySet iterator
 */
protected Iterator createKeySetIterator() {
    if (size() == 0) {
        return EmptyIterator.INSTANCE;
    }
    return new KeySetIterator(this);
}
 

/**
 * Creates a values iterator.
 * Subclasses can override this to return iterators with different properties.
 * 
 * @return the values iterator
 */
protected Iterator createValuesIterator() {
    if (size() == 0) {
        return EmptyIterator.INSTANCE;
    }
    return new ValuesIterator(this);
}
 

/**
 * Gets an iterator over all the collections in this composite.
 * <p>
 * This implementation uses an <code>IteratorChain</code>.
 *
 * @return an <code>IteratorChain</code> instance which supports
 *  <code>remove()</code>. Iteration occurs over contained collections in
 *  the order they were added, but this behavior should not be relied upon.
 * @see IteratorChain
 */
public Iterator iterator() {
    if (this.all.length == 0) {
        return EmptyIterator.INSTANCE;
    }
    IteratorChain chain = new IteratorChain();
    for (int i = 0; i < this.all.length; ++i) {
        chain.addIterator(this.all[i].iterator());
    }
    return chain;
}
 

/**
 * Gets an iterator for the collection mapped to the specified key.
 * 
 * @param key  the key to get an iterator for
 * @return the iterator of the collection at the key, empty iterator if key not in map
 * @since Commons Collections 3.1
 */
public Iterator iterator(Object key) {
    Collection coll = getCollection(key);
    if (coll == null) {
        return EmptyIterator.INSTANCE;
    }
    return coll.iterator();
}
 

/**
 * {@inheritDoc}
 */
@SuppressWarnings("unchecked")
@Override
public Iterator<IModulaSymbol> iterator() {
    IRecordTypeSymbol withExpressionType = ReferenceUtils.resolve(withExpressionTypeRef);
    if (withExpressionType == null) {
        return EmptyIterator.INSTANCE;
    }
    return withExpressionType.iterator();
}
 

@SuppressWarnings("unchecked")
public Iterator<Map<String, Object>> payloadIterator() {
    if ( isBatch() ) {
        return batch.iterator();
    }
    if ( properties != null ) {
        return new SingletonListIterator( properties );
    }
    return EmptyIterator.INSTANCE;
}
 

/**
 * Used for exception example
 */
@SuppressWarnings({ "unchecked", "unused" })
private void return_empty_iterator_apache_commons_exception () {
	
	DomainObject domain = null; // dao populate domain

	Iterator<String> strings;
	if (domain != null && !CollectionUtils.sizeIsEmpty(domain.getStrings())) {
		strings = domain.getStrings();
	} else {
		strings = EmptyIterator.INSTANCE;
	}
	
	//...
}