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Diffstat (limited to 'src/main/java/bjc/data')
| -rw-r--r-- | src/main/java/bjc/data/ResettableIterator.java | 106 |
1 files changed, 106 insertions, 0 deletions
diff --git a/src/main/java/bjc/data/ResettableIterator.java b/src/main/java/bjc/data/ResettableIterator.java new file mode 100644 index 0000000..2208fb2 --- /dev/null +++ b/src/main/java/bjc/data/ResettableIterator.java @@ -0,0 +1,106 @@ +package bjc.data; + +import java.util.*; + +/* + * @TODO Oct 6, 2020 - Ben Culkin - :CleverCache + * + * In the future, there are certain efficencies we could take with our cached + * elements; namely, the case where we repeat the same element multiple times, + * or the case where we have a mixture of identical (and probably sizable) elements + * + * The general downside to these of course, is that these efficencies would cost + * us something in terms of complexity, as well as not benefitting iterators which + * aren't large enough. + * + * Still an interesting thought as to the best way to implement such a thing though. + */ + +/** + * An iterator which can go back to the beginning of its iteration sequence at + * any point. + * + * @author Ben Culkin + * + * @param <T> + * The type iterated over. + */ +public class ResettableIterator<T> implements Iterator<T> { + private List<T> cache; + private Iterator<T> backing; + + private boolean isRepeating = false; + private Iterator<T> cacheIterator; + + /** + * Create a new resettable iterator. + * + * @param itr + * The iterator to iterate over. + */ + public ResettableIterator(Iterator<T> itr) { + backing = itr; + + cache = new ArrayList<>(); + } + + /** + * Create a new resettable iterator. + * + * @param itr + * The iterable to iterate over. + */ + public ResettableIterator(Iterable<T> itr) { + this(itr.iterator()); + } + + @Override + public boolean hasNext() { + if (isRepeating) { + return cacheIterator.hasNext() ? true : backing.hasNext(); + } else { + return backing.hasNext(); + } + } + + @Override + public T next() { + if (isRepeating) { + if (cacheIterator.hasNext()) { + return cacheIterator.next(); + } else { + cacheIterator = null; + isRepeating = false; + } + } + + T itm = backing.next(); + + cache.add(itm); + + return itm; + } + + /** + * Reset this iterator to its starting point. + */ + public void reset() { + isRepeating = true; + + cacheIterator = cache.iterator(); + } + + /** + * Clears the cache of items. + * + * This will immediately return the iterator to the last actual item from the + * sequence, as well as making that the first item to be iterated over in the + * future. + */ + public void clearCache() { + isRepeating = false; + cacheIterator = null; + + cache = new ArrayList<>(); + } +} |
