An earthquake measuring 5.4 on the Richter scale jolted western Java island of Indonesia on Saturday morning, the country\'s Meteorology and Geophysics Agency said.  The quake struck at 04:31 a.m. Jakarta time Saturday (2131 GMT Friday) with epicenter of 199 km southwest Ujungkulon of Banten province and with the depth of 10 km, the agency said.  Indonesia sits on a vulnerable quake-hit zone so called \"the Pacific Ring of fire.\"