Java  is one of the islands of the Greater Sunda Islands in Indonesia, bordered by the Indian Ocean to the south and the Java Sea on the north. With a population of 147.7 million (Java only) or 151.8 million (including the inhabitants of its surrounding islands, principally Madura), Java constitutes 56.1 percent of the Indonesian population and is the world’s most-populous major island. The Indonesian capital city, Jakarta, is on its northwestern coast. Much of the well-known part of Indonesian history took place on Java. It was the centre of powerful Hindu-Buddhist empires, the Islamic sultanates, and the core of the colonial Dutch East Indies.

Java was also the center of the Indonesian struggle for independence during the 1930s and 1940s. Java dominates Indonesia politically, economically and culturally. Four of Indonesia’s eight UNESCO world heritage sites are located in Java: Ujung Kulon National Park, Borobudur Temple, Prambanan Temple, and Sangiran Early Man Site.

Java is divided into four administrative provinces: Banten, West Java, Central Java, and East Java, and two special regions, Jakarta and Yogyakarta.

Despite its large population and in contrast to the other larger islands of Indonesia, Java is comparatively homogeneous in ethnic composition. Only two ethnic groups are native to the island—the Javanese and Sundanese. A third group is the Madurese, who inhabit the island of Madura off the northeast coast of Java, and have immigrated to East Java in large numbers since the 18th century.

According to wikipedia