How to use

ResourceCollection

in

org.apache.tools.ant.types

/**
 * Construct a new ConcatResourceInputStream
 * for the specified ResourceCollection.
 * @param rc the ResourceCollection to combine.
 */
 public ConcatResourceInputStream(ResourceCollection rc) {
   iter = rc.iterator();
 }

if (!rc.isFilesystemOnly() && !supportsNonFileResources()) {
  throw new BuildException(
    "Only FileSystem resources are supported.");
if (rc.isEmpty()) {
  throw new BuildException(MSG_WHEN_COPYING_EMPTY_RC_TO_FILE);
if (rc.size() == 1) {
  final Resource res = rc.iterator().next();
  final FileProvider r = res.as(FileProvider.class);
  if (file == null) {

/**
 * Add all resources in a resource collection to the source list.
 * @since Ant 1.7.1
 * @param collection the resource to load
 * @throws BuildException if a resource cannot be read
 */
public void loadResources(ResourceCollection collection) {
  collection.forEach(this::loadResource);
}

/**
 * Set the source resource.
 * @param a the resource to load as a single element Resource collection.
 */
public void addConfigured(ResourceCollection a) {
  if (a.size() != 1) {
    throw new BuildException(
      "only single argument resource collections are supported");
  }
  src = a.iterator().next();
}

/**
 * Take all elements except for the last <code>count</code> elements.
 * @return a Collection of Resources.
 */
@Override
protected Collection<Resource> getCollection() {
  int ct = getValidCount();
  ResourceCollection nested = getResourceCollection();
  if (ct > nested.size()) {
    return Collections.emptyList();
  }
  return nested.stream().limit((long) nested.size() - ct)
    .collect(Collectors.toList());
}

/**
 * whether the given resource collection is a (subclass of)
 * FileSet that only contains file system resources.
 * @param rc the resource collection to check.
 * @return true if the collection is a fileset.
 * @since Ant 1.7
 */
protected static boolean isFileFileSet(final ResourceCollection rc) {
  return rc instanceof FileSet && rc.isFilesystemOnly();
}

  /**
   * Learn whether this {@link ResourceCollection} is empty.
   * @return boolean
   */
  default boolean isEmpty() {
    return size() == 0;
  }
}

/**
 * Set the source resource.
 * @param a the resource to load as a single element Resource collection.
 * @since Ant 1.7
 */
public synchronized void addConfigured(ResourceCollection a) {
  if (src != null) {
    throw new BuildException("only a single source is supported");
  }
  if (a.size() != 1) {
    throw new BuildException(
        "only single-element resource collections are supported");
  }
  src = a.iterator().next();
}

private ResourceCollection createResourceCollection(Reference ref) {
 Object o = ref.getReferencedObject();
 if (!(o instanceof ResourceCollection)) {
   throw new BuildException("Only File based ResourceCollections are supported.");
 }
 ResourceCollection rc = (ResourceCollection) o;
 if (!rc.isFilesystemOnly()) {
   throw new BuildException("Only ResourceCollections from local file system are supported.");
 }
 return rc;
}

/**
 * Fulfill the condition contract.
 * @return true if the specified ResourceCollection satisfies the set criteria.
 * @throws BuildException if an error occurs.
 */
@Override
public boolean eval() {
  if (rc == null) {
    throw new BuildException(ONE_NESTED_MESSAGE);
  }
  if (count == null) {
    throw new BuildException(COUNT_REQUIRED);
  }
  return when.evaluate(Integer.valueOf(rc.size()).compareTo(count));
}

/**
 * Take the last <code>count</code> elements.
 * @return a Collection of Resources.
 */
@Override
protected Collection<Resource> getCollection() {
  int count = getValidCount();
  ResourceCollection rc = getResourceCollection();
  int size = rc.size();
  int skip = Math.max(0, size - count);
  List<Resource> result =
    rc.stream().skip(skip).collect(Collectors.toList());
  int found = result.size();
  if (found == count || (size < count && found == size)) {
    return result;
  }
  //mismatch:
  String msg = String.format(
    "Resource collection %s reports size %d but returns %d elements.",
    rc, size, found + skip);
  //size was understated -> too many results; warn and continue:
  if (found > count) {
    log(msg, Project.MSG_WARN);
    return result.subList(found - count, found);
  }
  //size was overstated; we missed some and are now in error-land:
  throw new BuildException(msg);
}

@Override
public boolean hasNext() {
  boolean result = ri != null && ri.hasNext();
  while (!result && rci.hasNext()) {
    ri = rci.next().iterator();
    result = ri.hasNext();
  }
  return result;
}
@Override

/**
 * Set the source resource.
 * @param a the resource to pack as a single element Resource collection.
 */
public void addConfigured(ResourceCollection a) {
  if (a.size() != 1) {
    throw new BuildException(
        "only single argument resource collections are supported as archives");
  }
  setSrcResource(a.iterator().next());
}

/**
 * Sets the archive that holds this as a single element Resource
 * collection.
 * @param a the archive as a single element Resource collection.
 */
public void addConfigured(ResourceCollection a) {
  super.addConfigured(a);
  if (!a.isFilesystemOnly()) {
    throw new BuildException("only filesystem resources are supported");
  }
}

/**
 * Execute as a Task.
 */
@Override
public void execute() {
  if (rc == null) {
    throw new BuildException(ONE_NESTED_MESSAGE);
  }
  if (property == null) {
    log("resource count = " + rc.size());
  } else {
    getProject().setNewProperty(property, Integer.toString(rc.size()));
  }
}

/**
 * Return a {@link Stream} over this {@link ResourceCollection}.
 * @return {@link Stream} of {@link Resource}
 * @since Ant 1.10.2
 */
default Stream<? extends Resource> stream() {
  final Stream.Builder<Resource> b = Stream.builder();
  forEach(b);
  return b.build();
}

private Resource getXest(ResourceCollection rc, ResourceComparator c) {
  return StreamUtils.iteratorAsStream(rc.iterator()).max(c).orElse(null);
}

/**
 * Set the source resource.
 * @param a the source resource collection.
 * @since Ant 1.7
 */
public void addConfigured(ResourceCollection a) {
  if (a.size() != 1) {
    throw new BuildException(
      "only single argument resource collections are supported.");
  }
  setSrcResource(a.iterator().next());
}

private ResourceCollection createResourceCollection(Reference ref) {
 Object o = ref.getReferencedObject();
 if (!(o instanceof ResourceCollection)) {
  throw new BuildException("Only File based ResourceCollections are supported.");
 }
 ResourceCollection rc = (ResourceCollection) o;
 if (!rc.isFilesystemOnly()) {
  throw new BuildException("Only ResourceCollections from local file system are supported.");
 }
 return rc;
}

/**
 * Efficient size implementation.
 * @return int size
 */
@Override
public synchronized int size() {
  return Math.min(getResourceCollection().size(), getValidCount());
}