Why's Java popular? Because its easy to use and nearly cross platform (You mustn't expect to run a Java App for Desktop on your Java supported Cellphone, without some changes, or quite many). Java is free, so development costs are just for the Human resource, not the software.
Java is a hassle free, and a high level language, so easier to learn. You don't have to manage memory, you can focus just on the purpose of the Application. Java program is secure (in the sense, that it is less error prone and thus harder to break). Java is like 'all under one roof'. With standard C/C++, there are no inbuilt Graphics/GUI/Sound/Networking provisions, everything comes separately, as libraries.