MongoDB: obtains the most value of a field in Java.

In Shell operations, we can use Max or min to obtain the maximum value. Or we can use sort and limit to get the most value.

It seems that Max and Min cannot be used in Java, but we can make some modifications to the latter method.

DB. t1.insert ({"_ id": 1, "Hour": 0, "cycletime": 0}) dB. t1.insert ({"_ id": 2, "Hour": 0, "cycletime": 1}) dB. t1.insert ({"_ id": 3, "Hour": 0, "cycletime": 2}) dB. t1.insert ({"_ id": 6, "Hour": 0, "downtime": 6}) dB. t1.insert ({"_ id": 4, "Hour": 0, "cycletime": 3}) dB. t1.insert ({"_ id": 5, "Hour": 1, "cycletime": 4}) dB. t1.insert ({"_ id": 7, "Hour": 1, "downtime": 9 })

The data is as above. If we take the maximum value for hour, we should return the last two documents with the ID of 5, 7.

Basicdbobject keys = new basicdbobject (); keys. put ("Hour",-1); dbcursor cursor = Coll. find (). sort (KEYS ). limit (2); While (cursor. hasnext () {system. out. println (cursor. next (). tostring ());}