Android is a mobile operating system developed by Google, based on a modified version of the Linux kernel and other open source software and designed primarily for touchscreen mobile devices such as smartphones and tablets.
iOS is a mobile operating system created and developed by Apple Inc. exclusively for its hardware. It is the operating system that presently powers many of the company's mobile devices, including the iPhone, iPad, and iPod Touch.
BlackBerry is a Canadian multinational company specializing in enterprise software and the Internet of things. Originally known as Research In Motion (RIM), it is best known to the general public as the former developer of the BlackBerry brand of smartphones, and tablets.
Java is a general-purpose computer-programming language that is concurrent, class-based, object-oriented, and specifically designed to have as few implementation dependencies as possible.