The Android operating system has reportedly generated $31 billion in revenues for Google since it first launched in 2008, creating $22 billion in profits largely from mobile advertising.

The information was revealed at a court hearing last week by a lawyer for Oracle, which is suing Google on the accusation that it used Java to develop Android without paying for it, according to Bloomberg. In a more recent filing, Google protested the lawyer's disclosure, arguing that it was based on confidentially shared internal documents and that parts of the public transcript of the hearing should be redacted and sealed.

The transcript in fact disappeared from electronic court records on Thursday afternoon without any sign of a ruling on Google's request.

Google makes most of its Android-based revenue from mobile ads, or from a cut of app sales on Google Play. The company does sell branded phones and tablets, but these are developed in cooperation with third-party hardware makers and are often deliberately sold at a lower profit margin as showcase devices. Most Android hardware revenue is generated outside of Google.