Is it easy to use?

A few friends who want to learn j2s asked me this question. I think there are two answers to this question.

It is simple.

The primary reason for its simplicity is that Java is used in the development of J2SE and Java is simple, or "concise" is more powerful. Compared with the C ++ program Code, Java Code looks more comfortable and intuitive.

On the other hand, the Java SDK is rich and easy to configure. If you use a powerful IDE (such as JB and Eclipse, I prefer JB in the Development of Java SDK ), so there is a certain degree of Java foundation, it is not difficult to get started with J2EE.

It is not simple.

For more people, it is simple because it is "small". The so-called "small" is mainly aimed at a small number of APIs. "I have finished learning in two or three weeks," someone said. However, I cannot agree with this opinion. In fact, it is precisely because it provides a small number of APIs that make j2_based programming more challenging than traditional programming. Compared with J2SE and J2EE that provide rich APIs, we need to be "self-reliant" in a much larger scope. Only some APIs provide us with the most basic functions, and the rest will be explored by programmers themselves. If all the functions you need have been implemented by existing APIs, we don't need to study any more. We only need an API manual.

The second difficulty of j2m's is its high limitation. Of course, this is also a common problem faced by all mobile device-based development. The memory limit and processing speed limit make us have to discard a lot of beautiful things, optimize every line of code as much as possible, optimize and optimize, and find a balance between memory usage and performance .. in j2s, we must not only reduce the creation of objects, but also minimize the number of object references. The excellent applications, games, and software developed under such conditions can be said to be more valuable than the development on the desktop platform.

Third, it is also a public problem facing mobile development: it is difficult to adapt multiple models. Different from the desktop platform, mobile devices differ greatly from each other, from hardware screen resolution, memory, processor to underlying KVM implementation, to the degree of support for the j2's specifications, this makes the promise of "one compilation, running everywhere" almost a joke. However, in any case, it is still the best choice for cross-platform mobile applications. Because smartphones and traditional mobile phones support Java regardless of the system they use. Even if you need to make multiple changes, the cost is much lower. At the same time, it also tests the design capabilities of programmers. A well-designed program can minimize the cost of adaptation.

The last problem is that KVM has many bugs, but Sun does not seem to be responsible for this. Everyone knows that Java is developed in two steps: specification and implementation. Sun and many vendors have established specifications, which are then implemented by each vendor based on their own devices. However, I don't know if the design level of the manufacturer is limited. At present, the KVM implementation of many models is not satisfactory, and the Bug is just like a cool Bug, such as the most typical Nokia 6600, people who have actually done development for it should have a deep understanding. This makes it more difficult for developers to adapt to multiple models. These bugs can fully test the debugging capabilities of programmers :) but over time, I believe this will be improved, and Nokia has been releasing software upgrades for the S60 model to fix these bugs. However, you can't think about using the S40 model of the closed operating system (in fact, the S40 bug is much less ).

To sum up, the introduction of j2's is not as simple as most people think, or it is simple, but to be "proficient ", you also need to master various programming and debugging skills with mobile development characteristics, which is not a one-stop task.