Partition key not working properly

Hi all,

I'm struggling with how to use the partition key mechanism properly. My logic is set the partition number as 3, then create three partition keys as "0", "1", "2", then use the partition keys to create three KeyedMessage such as
KeyedMessage(topic, "0", message),
KeyedMessage(topic, "1", message),
KeyedMessage(topic, "2", message)

After this, creating a producer instance to send out all the KeyedMessage.

I expecting each KeyedMessage should enter to different partitions according to the different partition keys, which means
KeyedMessage(topic, "0", message) go to Partition 0,
KeyedMessage(topic, "1", message) go to Partition 1,
KeyedMessage(topic, "2", message) go to Partition 2

I'm using Kafka-web-console to watch the topic status, but the result is not like what I'm expecting. KeyedMessage still go to partitions randomly, some times two KeyedMessage will enter the same partition even they have different partition keys, .

Not sure whether my logic is incorrect or I didn't understand the partition key mechanism correctly. Anyone could provides some sample code or explanation would be great!

Thanks,
Haoming