Memcached的incr 和 decr命令用于增加現(xiàn)有鍵的數(shù)值遞減。如果鍵未找到或如果關(guān)鍵的不是數(shù)字，則返回NOT_FOUND。那么CLIENT_ERROR不能增加或返回遞減非數(shù)值錯(cuò)誤。

Incr

語法

memcached的incr命令的基本語法如下所示：

incr key increment_value

示例

set visitors 0 900 2
10
STORED
get visitors
VALUE visitors 0 2
10
END
incr visitors 5
15
get visitors
VALUE visitors 0 2
15
END

在上面的例子中，我們已經(jīng)使用visitors為一個(gè)鍵，并設(shè)置10為初始值，之后為visitors增量5。

Decr

語法

memcached的decr命令的基本語法如下所示：

decr key decrement_value

示例

set visitors 0 900 2
10
STORED
get visitors
VALUE visitors 0 2
10
END
decr visitors 5
5
get visitors
VALUE visitors 0 1
5
END

使用Java應(yīng)用程序遞增遞減數(shù)據(jù)

要在memcached服務(wù)器增加，減小數(shù)據(jù)，需要使用memcached的incr, decr方法。

示例

import net.spy.memcached.MemcachedClient;
public class MemcachedJava {
   public static void main(String[] args) {
      //Connecting to Memcached server on localhost
      MemcachedClient mcc = new MemcachedClient(new InetSocketAddress("127.0.0.1", 11211));
      System.out.println("Connection to server sucessfully");
      System.out.println("set status:"+mcc.set("count", 900, "5").isDone());
      //Get value from cache
      System.out.println("Get from Cache:"+mcc.get("count"));
      // now increase the stored value
      System.out.println("Increment value:"+mcc.incr("count", 2));
      // now decrease the stored value
      System.out.println("Decrement value:"+mcc.decr("count", 1));
      // now get the final stored value
      System.out.println("Get from Cache:"+mcc.get("count"));
   }
}

輸出

當(dāng)上述程序編譯和運(yùn)行，它提供了以下的輸出：

Connection to server successfully
set status:true
Get from Cache:5
Increment value:7
Decrement value:6
Get from Cache:6