### Question:
HMapKL implements MapKL<K>, Cloneable, Serializable { @Override public long dot(MapKL<K> m) { long s = 0; for (MapKL.Entry<K> e : m.entrySet()) { K key = e.getKey(); if (this.containsKey(key)) { s += this.get(key) * e.getValue(); } } return s; } @SuppressWarnings("unchecked")  HMapKL(int initialCapacity, float loadFactor);  HMapKL(int initialCapacity); @SuppressWarnings("unchecked")  HMapKL();  HMapKL(MapKL<? extends K> m); int size(); boolean isEmpty(); long get(K key); boolean containsKey(K key); long put(K key, long value); void putAll(MapKL<? extends K> m); long remove(K key); void clear(); boolean containsValue(long value); @SuppressWarnings("unchecked") Object clone(); Set<K> keySet(); Collection<Long> values(); Set<MapKL.Entry<K>> entrySet(); String toString(); @Override void plus(MapKL<K> m); @Override long dot(MapKL<K> m); @Override void increment(K key); @Override void increment(K key, long value);  }### Answer:
@Test public void testDot() throws IOException { HMapKL<String> m1 = new HMapKL<String>(); m1.put("1", 2L); m1.put("2", 1L); m1.put("3", 3L); m1.put("" + Integer.MAX_VALUE, (long) Integer.MAX_VALUE); HMapKL<String> m2 = new HMapKL<String>(); m2.put("1", 1L); m2.put("2", 4L); m2.put("4", 5L); m2.put("" + Integer.MAX_VALUE, (long) Integer.MAX_VALUE); long s = m1.dot(m2); assertTrue(s > Integer.MAX_VALUE); assertEquals((long) Integer.MAX_VALUE * Integer.MAX_VALUE + 6L, s); }