Increment the number stored at key by one. If the key does not exist or contains a value of a wrong type, set the key to the value of "0" before to perform the increment operation.
INCR commands are limited to 64 bit signed integers.
Note: this is actually a string operation, that is, in Redis there are not "integer" types. Simply the string stored at the key is parsed as a base 10 64 bit signed integer, incremented, and then converted back as a string.
Time complexity: O(1)
@see #incrBy(String,long)
@see #decr(String)
@see #decrBy(String,long)
@param key
@return Integer reply, this commands will reply with the new value of keyafter the increment.