### Question:
Int2LongOpenHashMapWritable extends Int2LongOpenHashMap implements Writable { public void increment(int key) { increment(key, 1); } Int2LongOpenHashMapWritable(); void readFields(DataInput in); void decode(); boolean hasBeenDecoded(); void write(DataOutput out); byte[] serialize(); static Int2LongOpenHashMapWritable create(DataInput in); static Int2LongOpenHashMapWritable create(byte[] bytes); void plus(Int2LongOpenHashMapWritable m); long dot(Int2LongOpenHashMapWritable m); void increment(int key); void increment(int key, long n); static void setLazyDecodeFlag(boolean b); static boolean getLazyDecodeFlag(); int[] getKeys(); long[] getValues(); void lazyplus(Int2LongOpenHashMapWritable m); Int2LongMap.Entry[] getEntriesSortedByValue(); Int2LongMap.Entry[] getEntriesSortedByValue(int k);  }### Answer:
@Test public void testIncrement() throws IOException { Int2LongOpenHashMapWritable m = new Int2LongOpenHashMapWritable(); m.put(2, 7L); m.put(1, 29L); assertEquals(7L, m.get(2)); assertEquals(29L, m.get(1)); m.increment(2); m.increment(1); m.increment(3); assertEquals(8L, m.get(2)); assertEquals(30L, m.get(1)); assertEquals(1L, m.get(3)); m.increment(1, 3L); m.increment(3, 5L); assertEquals(8L, m.get(2)); assertEquals(33L, m.get(1)); assertEquals(6L, m.get(3)); }