Hello and welcome to Java Ranch.
I can answer some of your questions. I'm sure other people will answer the others and expeand on my answers.
#1 - I've not used NetBeans in many many years (I currently use a different IDE), but most IDEs when being used to generate GUI based code do not allow for manual alteration of the code, or at least not easily. I personally would recommend hand writing your code from scratch while you are first learning. That way you can make changes and can understand the code better. Than when you start using the IDE to generate the code, you will have a better understanding of what it is doing.
#2 & #3 - you night want to ask these questions in the
IDEs, Version Control and other tools forum. Since I haven't used NetBeans in years, I can't answer these. But see my discussion on using an IDE below in the answer to #5.
#4 - Java is just as fast as C#. The statement that Java is slow is an old and unfortunate myth about Java. And one that is constantly perpetuated by some people who prefer the C, C++ or C# languages. In its very early days of its life (1995), Java was slower than it is today; but it was never so slow as to be unusable. It was more with client side code than server side code that it was a bit slower. Nevertheless, it was never as slow as some people like to make out. But with better processors today, and vast improvements in Just In Time Compiling, Java is just as fast as C or C#. In fact I have seen demos where Java was faster than C. And speed depends more on the quality of the code and the skill of the developer. Bad code in any language will be slow.
Opinions will vary greatly on this subject. And unfortunately too often opinions on the subject are stated as if the are fact. It is a very emotional subject for some. My advice would be to simply ask anyone who says Java is slow to prove it with hard facts that are current. In regards to C# being easier to learn, that is hard to say. One advantage -- or disadvantage depending on your perspective -- of C# is that everything is done by Microsoft - C# the language, the IDE, the OS you will being using, etc. This might make it a bit easier to learn for some. But for others it may make it harder. Again, this is an area where people's opinion will differ. If you want to be able to program on Linux, then I would suggest sticking with Java, or learning C++, but not C#. Java can be written on any platform, and then run anywhere. So you can learn Java on Windows for now, and then when you are ready to learn Linux, you can run your Java programs on it and will not have to learn anything new about the language. If you use C++, you can learn on Windows, but when you move to Linux, there will be a bit of learning to do since compiling C++ code on Linux can be different than on Windows. And C#, to the best of my knowledge, cannot be run on Linux. One thing you will learn is that when it comes to language selection, people can be very opinionated about their language of choice. Some C++/C# users will tell you how crappy Java is because they are C++/C# users. Likewise some Java users will tell you how crappy C++/C# are because they are Java users. They are all good languages, but are used by different people. In my humble opinion, I think you will find more resources for learning Java than C# since many universities use Java as their language when teaching. That's not to say you won't find things on C#. I just think you will find more on Java. But again, I am a strong Java user of many years, so my perceptions are naturally biased because of that.
#5 - My advice is to concentrate on learning Java first... without using an IDE. Right now it seems as if you are trying too hard to learn the IDE and that is preventing you from learning the language. The best developers I work with learned to program outside and IDE first. An IDE like NetBeans is a very powerful tool. But to use it effectively, you need to understand the under workings of a language first. I cannot stress this enough. It's like people who only know how to use a calculator but cannot add 2 + 3 by hand. If you read other posts here at JavaRanch, you will see many others will provide this advice.
As for a suggestion of where to start, try the book
Head First Java, Second Edition. It is one of the best Java books on the market and has been a #1 selling book for many years. Work through the exercises in the book. If you have questions, you can ask here in the forums. Type the sample code in and play with it. See what happens when you change things. The best way to learn to program is to experiment. You can look at
The Java Tutorial which walks you through some of the basics in Java. You can also look at the
Cattle Drive here at JavaRanch. The Cattle Drive is a self paced tutorial you can work through with exercises. And you can get feedback on the exercises as you do them.
In regards to your statement:
I found i failed bcz i must add myql library to project library(this is really annoying).
This is one of the things that makes Java so powerful. I can write database code in Java and then run it against a MySQL DB, Oracle DB, Hypersonic DB, Derby DB, SQL serve DBr, or any number of other databases simply by changing a library file. And I can run it on any OS. That is very powerful. An unfortunate part of that powerfulness is that it can make learning the language a bit more challenging because it might not be quite as quick to use. You are not just up and running instantly because everything is preconfigured for you. But in the long run, it will allow you to write much more powerful code. Hanging in there through that learning process will provide great rewards in the end.
Try not to learn too much at once. Take your time and learn one thing at a time. You are asking questions in this post about an IDE, a plug-in for an IDE, Java, GUI code, and databases. These are all hefty topics on their own. Combine, it is a lot for anyone to learn all at once.
