How to start learning java ?

It doesn't really matter where you start at using modern programming languages and a GUI IDE development application. You can learn the theories of programming and the methodologies for best software practices utilizing any language. It seems people that started programming in 1960-1980's will recommend starting with a language that has an command prompt application because they claim the less functionality that is in the software; the more that you will pay attention to the programming language instead of being confronted with the functionality of the IDE development application. Visual Basic is a nice language to start with. You can get the Express Edition of Visual Basic, C#, Visual C++ at microsoft.com. Of course, you can only make Window compatible software, so you would need to use an emulator or vmware type program under a compatible windows operating system for the .NET library. If you go with Java, some good text editors are JCreator and BlueJ. I think another one is called "TextPad" and it seems to be popular with a vast arraylist of programming language. It supports syntax highlighting, not sure if the program will launch the programs to compile the code, but it might have the functionality. JCreator is a very good program but it is for Java, hence the J. It supports the syntax highlighting so that kind of helps you spot the commands in your code. BlueJ is very basic, but it is a nice program with little functionality to get in the way of learning the programming language syntax. But anyway, it doesn't matter where you start. Pick a language and stick with it. Look for source code on the Internet and see what language is the most popular with the types of programs that are already written that interests you. Then you can learn the syntax of that language and continue learning from the zillions of lines of code that is spread out all across the Internet. You need good learning resources, you need good reference resources, you need to have access to source code that interests you, and you need great freeware or inexpensive development software for your programming language while you walk down the road to being a professional computer programmer. There is more than that, that you need, but it is good for now. There is other area; one particular is utilizing software development methodologies. Basically, you learn to keep software development cost to a budget. You start out by making sure that it is worth the time and effort to develop such a program. You design logically how the functionality of the program will work through diagramming (not just flow-charts). You will need diagrams of how systems will behave and interact when the functionalities of the software being developed is executed. You will need to throw out some storyboarding (some mock-up screen-shots of the GUI of your application). Some medium size companies will use software to protect different aspects of the program. Basically, each programmer will do their own thing. They will be given program documentation on what functions to call, and whether to create a wrapper class (or use a static method). Most likely all an individual programmer will have access to is another programmer's api (application programming interface). Keeps the programming environment simpler, easier to manage, know exactly who is responsible for what code, and keeps a malicious programmer from getting into someone else program and committing harm to the work that that particular employee is responsible for and it prevents an employee from copy and pasting all the source code files and take it home to compile and release to the world for free or sell under your own software title.

Your teacher is wrong. You do not need to learn C++ before learning Java. That's absurd. If you want to learn Java, pick up a book and get reading and coding.

Download Eclipse and see if you can audit the class and follow along.