Shrink TEMP Tablespace using alter tablespace command
SQL> ALTER TABLESPACE temp SHRINK SPACE KEEP 50M;.

Shrink TEMPFILE using alter tablespace command
SQL> ALTER TABLESPACE temp SHRINK TEMPFILE '/u01/app/oracle/oradata/TEST11G/temp01.dbf' KEEP 40M;

Shrink TEMP Tablespace to the smallest possible size:
SQL> ALTER TABLESPACE temp SHRINK SPACE;