private static <T> long countInternal(BatchingVisitable<T> visitable, int batchSize) {
final long[] count = new long[1];
visitable.batchAccept(
batchSize,
AbortingVisitors.batching(
new AbortingVisitor<T, RuntimeException>() {
@Override
public boolean visit(Object item) {
count[0]++;
return true;
}
}));
return count[0];
}
@Nullable
public static <T> T getLast(BatchingVisitable<T> visitable, @Nullable T defaultElement) {
final Mutable<T> ret = Mutables.newMutable(defaultElement);
visitable.batchAccept(
DEFAULT_BATCH_SIZE,
AbortingVisitors.batching(
new AbortingVisitor<T, RuntimeException>() {
@Override
public boolean visit(T item) {
ret.set(item);
return true;
}
}));
return ret.get();
}
public static <T> boolean isEqual(BatchingVisitable<T> v, final Iterator<T> it) {
boolean ret =
v.batchAccept(
DEFAULT_BATCH_SIZE,
new AbortingVisitor<List<T>, RuntimeException>() {
@Override
public boolean visit(List<T> batch) {
Iterator<T> toMatch = Iterators.limit(it, batch.size());
return Iterators.elementsEqual(toMatch, batch.iterator());
}
});
if (it.hasNext()) {
return false;
}
return ret;
}
/**
* This will return the first maximal element in the visitable. This method takes a default
* element and will return that if the visitable is empty. If the visitable is non-empty it will
* return the largest value in the visitable.
*
* <p>A common way to use this would be to pass <code>null</code> as the defaultElement and have
* the ordering throw on null elements so you know the visitable doesn't have any nulls.
*/
public static <T> T getMin(
BatchingVisitable<T> v, final Ordering<? super T> o, @Nullable T defaultElement) {
final Mutable<T> ret = Mutables.newMutable(defaultElement);
v.batchAccept(
DEFAULT_BATCH_SIZE,
AbortingVisitors.batching(
new AbortingVisitor<T, RuntimeException>() {
boolean hasSeenFirst = false;
@Override
public boolean visit(T item) throws RuntimeException {
if (hasSeenFirst) {
ret.set(o.min(ret.get(), item));
} else {
// Call o.max here so it will throw if item is null and this
// ordering hates on nulls.
ret.set(o.min(item, item));
hasSeenFirst = true;
}
return true;
}
}));
return ret.get();
}
public static <T> boolean isEmpty(BatchingVisitable<T> v) {
return v.batchAccept(1, AbortingVisitors.batching(AbortingVisitors.<T>alwaysFalse()));
}
