What is the best way to reduce tablespace size (defragmentation of tablespace) ?

SQL> select sum(bytes)/1024/1024/1024 from dba_extents where tablespace_name='APPS_TS_TX_DATA';

SUM(BYTES)/1024/1024/1024

-------------------------

212.016541

SQL> select sum(bytes)/1024/1024/1024 from dba_data_files where tablespace_name='APPS_TS_TX_DATA';

SUM(BYTES)/1024/1024/1024

-------------------------

4193.01563