### Question:
Roaring64Bitmap implements Externalizable, LongBitmapDataProvider { @Override public String toString() { final StringBuilder answer = new StringBuilder(); final LongIterator i = this.getLongIterator(); answer.append("{"); if (i.hasNext()) { answer.append(i.next()); } while (i.hasNext()) { answer.append(","); if (answer.length() > 0x80000) { answer.append("..."); break; } answer.append(i.next()); } answer.append("}"); return answer.toString(); } Roaring64Bitmap(); void addInt(int x); @Override void addLong(long x); @Override long getLongCardinality(); int getIntCardinality(); @Override long select(final long j); Iterator<Long> iterator(); @Override void forEach(final LongConsumer lc); @Override long rankLong(long id); void or(final Roaring64Bitmap x2); void xor(final Roaring64Bitmap x2); void and(final Roaring64Bitmap x2); void andNot(final Roaring64Bitmap x2); @Override void writeExternal(ObjectOutput out); @Override void readExternal(ObjectInput in); @Override String toString(); @Override LongIterator getLongIterator(); @Override boolean contains(long x); @Override int getSizeInBytes(); @Override long getLongSizeInBytes(); @Override boolean isEmpty(); @Override ImmutableLongBitmapDataProvider limit(long x); boolean runOptimize(); @Override void serialize(DataOutput out); void serialize(ByteBuffer byteBuffer); void deserialize(DataInput in); void deserialize(ByteBuffer in); @Override long serializedSizeInBytes(); void clear(); @Override long[] toArray(); static Roaring64Bitmap bitmapOf(final long... dat); void add(long... dat); void add(final long rangeStart, final long rangeEnd); @Override LongIterator getReverseLongIterator(); @Override void removeLong(long x); @Override void trim(); @Override int hashCode(); @Override boolean equals(Object obj); void flip(final long x); @Override Roaring64Bitmap clone();  }### Answer:
@Test public void testToString() { Roaring64Bitmap map = newDefaultCtor(); map.addLong(123); map.addLong(Long.MAX_VALUE); map.addLong(Long.MAX_VALUE + 1L); assertEquals("{123,9223372036854775807,-9223372036854775808}", map.toString()); }