### Question:
MiniRepository implements Repository { public boolean exists(@Nullable ID subject, @Nullable UID predicate, @Nullable NODE object, @Nullable UID context) { return findStatements(subject, predicate, object, context, false).hasNext(); } MiniRepository();  MiniRepository(int initialCapacity);  MiniRepository(int initialCapacity, boolean inverseIndex);  MiniRepository(STMT... stmts); void add(STMT... stmts); void clear(); @Override void close(); @Override void load(Format format, InputStream is, @Nullable UID context, boolean replace); @Override void export(Format format, Map<String, String> ns2prefix, UID context, OutputStream out); @Override void export(Format format, UID context, OutputStream out); @SuppressWarnings("unchecked") CloseableIterator<STMT> findStatements(@Nullable ID subject, @Nullable UID predicate, @Nullable NODE object, @Nullable UID context, boolean includeInferred); boolean exists(@Nullable ID subject, @Nullable UID predicate, @Nullable NODE object, @Nullable UID context); MiniDialect getDialect(); synchronized long getNextLocalId(); void index(ID key, STMT stmt, Map<ID, PredicateCache> index); @Override void initialize(); MiniConnection openConnection(); void remove(@Nullable ID subject, @Nullable UID predicate, @Nullable NODE object, @Nullable UID context); void removeStatements(Collection<STMT> stmts); @Override RT execute(RDFConnectionCallback<RT> operation);  }### Answer:
@Test public void Exists() { assertTrue(repository.exists(null, null, null, null)); repository.remove(null, null, null, null); assertFalse(repository.exists(null, null, null, null)); }