As much as I hate Oracle, there are huge advantages to Java. Java is strongly typed, free, and runs damn near anywhere. It's pretty much the go-to language when people think about OOP and for good reason. It has some excellent open source IDE support and it's widely used in the industry. With the current OpenJDK setup, it's also free of Oracle's licensing issues. It runs fast and can support most algorithms you'll probably ever study, without the manual memory management troubles of something like C++.

I was taught C# in uni for very similar reasons except the entire uni ran on Windows and the Microsoft platform, which made doing assignments on Linux rather inconvenient. With the status of dotnet core, I'd say Java finally has a good competitor when it comes to teaching OOP languages.