JAVA J2EE 4 U

 SELECT 

    t.schemaname AS schema_name,

    t.relname AS table_name,

    pg_size_pretty(pg_total_relation_size(i.indexrelid)) AS index_size

FROM 

    pg_stat_user_indexes i 

JOIN 

    pg_stat_user_tables t 

ON 

    i.relid = t.relid

ORDER BY 

    pg_total_relation_size(i.indexrelid) DESC;