Implementation of Redis

version-> 1.0.1

Latest changes in new update:

1. All values should be inside double-quotes. Ex- SET myKey "hello world!"
2. Multiple words are allowed as values in all opertions

Instructions to run:

1. Make sure your system has java installed in it
2. Download the Redis.java file from here
3. Open terminal and go to your directory where you've downloaded the file
4. Type javac Redis.java
5. java Redis

For now, only these functions are allowed:

1. SET: The SET command supports a set of options that modify its behavior:

   • EX seconds -- Set the specified expire time, in seconds.

   • PX milliseconds -- Set the specified expire time, in milliseconds.

   • NX -- Only set the key if it does not already exist.

   • XX -- Only set the key if it already exist.

       Examples: redis>SET mykey "hello"
                 OK
                 redis>SET mykey "hi" NX
                 Error
                 redis>SET mykey "hey" XX
                 OK
                 redis>SET mykey "world" EX 10
                 ok
             
                 After 10 seconds
                 redis>GET mykey
                 Nil
     

2. GET: Get the value of key. If the key does not exist the special value nil is returned.
   An error is returned if the value stored at key is not a string, because GET only handles string values.

        Examples: redis>GET mykey
                  Nil
                  redis>SET mykey "hello"
                  OK
                  redis>GET mykey
                  hello
   

3. EXPIRE: Set a timeout on key. After the timeout has expired, the key will automatically be deleted. A key with an associated timeout is often said to be volatile in Redis terminology.

           Examples: redis>SET mykey "hello"
                     OK
                     redis>EXPIRE mykey 5
                     1
                     
                     After 5seconds                          
                     redis>GET mykey
                     Nil
   

4. ZADD: ZADD supports a list of options, specified after the name of the key and before the first score argument. Options are:

   • XX: Only update elements that already exist. Never add elements.

   • NX: Don't update already existing elements. Always add new elements.

   • CH: Modify the return value from the number of new elements added, to the total number of elements changed (CH is an abbreviation of -changed). Changed elements are new elements added and elements already existing for which the score was updated. So elements specified in the command line having the same score as they had in the past are not counted. Note: normally the return value of ZADD only counts the number of new elements added.

      Examples: redis>ZADD myzset 1 "a"
                1
                redis>ZRANGE myzset 0 1 WITHSCORES
                a
                1
                redis>ZADD myzset 3 "c" 2 "b"
                2
                redis>ZRANGE myzset 0 -1 WITHSCORES
                a
                1
                b 
                2
                c 
                3
     

5. ZRANK: If member exists in the sorted set, Integer reply: the rank of member. If member does not exist in the sorted set or key does not exist, Bulk string reply: nil. (ranks start from 0)

        Examples: redis>ZADD myzset 1 "a" 3 "c" 2 "b"
                  3
                  redis>ZRANK myzset "a"
                  0
                  redis>ZRANK myzset "b"
                  2
                  redis>ZRANK myzset "c"
                  3
   

6. ZRANGE: Returns list of elements in the specified range (optionally with their scores, in case the WITHSCORES option is given).

         Examples: redis>ZADD myzset 1 "a" 3 "c" 2 "b"
                   3
                   redis>ZRANGE myzset 0 3
                   a
                   b
                   c
                   redis>ZRANGE myzset 0 -1 WITHSCORES
                   a
                   1
                   b
                   2
                   c
                   3
   

P.S.: USE QUIT to exit from the loop :)

Future scope:

• Support multi words for values and values should be inside "" ----DONE
• Implement Socket programming for providing server-client nature ----check redis/extraFeatures branch
• Code improvements