### Question:
Int2IntOpenHashMapWritable extends Int2IntOpenHashMap implements Writable { public void lazyplus(Int2IntOpenHashMapWritable m) { int[] k = m.getKeys(); int[] v = m.getValues(); for (int i = 0; i < k.length; i++) { if (this.containsKey(k[i])) { this.put(k[i], this.get(k[i]) + v[i]); } else { this.put(k[i], v[i]); } } } Int2IntOpenHashMapWritable(); @Override void readFields(DataInput in); void decode(); boolean hasBeenDecoded(); @Override void write(DataOutput out); byte[] serialize(); static Int2IntOpenHashMapWritable create(DataInput in); static Int2IntOpenHashMapWritable create(byte[] bytes); void plus(Int2IntOpenHashMapWritable m); long dot(Int2IntOpenHashMapWritable m); void increment(int key); void increment(int key, int n); static void setLazyDecodeFlag(boolean b); static boolean getLazyDecodeFlag(); int[] getKeys(); int[] getValues(); void lazyplus(Int2IntOpenHashMapWritable m); Int2IntMap.Entry[] getEntriesSortedByValue(); Int2IntMap.Entry[] getEntriesSortedByValue(int k);  }### Answer:
@Test public void testLazyPlus() throws IOException { Int2IntOpenHashMapWritable m1 = new Int2IntOpenHashMapWritable(); m1.put(1, 5); m1.put(2, 22); Int2IntOpenHashMapWritable m2 = new Int2IntOpenHashMapWritable(); m2.put(1, 4); m2.put(3, 5); Int2IntOpenHashMapWritable.setLazyDecodeFlag(true); Int2IntOpenHashMapWritable m3 = Int2IntOpenHashMapWritable.create(m2.serialize()); assertEquals(0, m3.size()); m1.lazyplus(m3); assertEquals(3, m1.size()); assertEquals(9, m1.get(1)); assertEquals(22, m1.get(2)); assertEquals(5, m1.get(3)); Int2IntOpenHashMapWritable.setLazyDecodeFlag(false); }