In the long history of programming languages, if one language can take the honor of being the most successful one so far then that language has to be Java.
Java has enjoyed its unique position of being a multi-faceted language. Be it network/internet programming which it catered through applets, or desktop programming or robust enterprise applications, you name it and Java could, and still is, able to take care of it.
Java also bridged the gap created because of the presence of multiple operating systems using its principle of write-once-run-anywhere. All these abilities made Java first choice of developers, leading to creation of a strong community which kept strengthening the language further.
But things have been changing in recent times. As shared in the post here, popularity of browsers and related technologies has been increasing steadily.