The decrement methods reduce the value of a given key if the corresponding value can be parsed to an integer value. These operations are provided at a protocol level to eliminate the need to get, update, and reset a simple integer value in the database. All the Java Client Library methods support the use of an explicit offset value that will be used to reduce the stored value in the database.

The first form of the decr() method accepts the keyname and offset value to be used when reducing the server-side integer. For example, to decrement the server integer dlcounter by 5:

client.decr("dlcounter",5);

The return value is the updated value of the specified key.

The second form of the decr() method will decrement the given key by the specified offset value if the key already exists, or set the key to the specified default value if the key does not exist. This can be used in situations where you are recording a counter value but do not know whether the key exists at the point of storage.

For example, if the key dlcounter does not exist, the following fragment will return 1000:

long newcount =
    client.decr("dlcount",1,1000);

System.out.printf("Updated counter is %d\n",newcount);

A subsequent identical call will return the value 999 as the key dlcount already exists.

The third form of the decr() method the decrement operation, with a default value and with the addition of setting an expiry time on the stored value. For example, to decrement a counter, using a default of 1000 if the value does not exist, and an expiry of 1 hour (3600 seconds):

long newcount =
    client.decr("dlcount",1,1000,3600);

For information on expiry values, see Section 4.4, “Expiry Values”.

The asynchronous form of the asyncDecr() method enables you to decrement a value without waiting for a response. This can be useful in situations where you do not need to know the updated value or merely want to perform a decrement and continue processing.

For example, to asynchronously decrement a given key:

OperationFuture<Long> decrOp =
    client.asyncDecr("samplekey",1,1000,24000);