Java simplified

Java programs are either Applets or Applications. The first one runs under an HTML environment in a browser window, the later runs standalone like we are used to thinking about how programs run. Most of the commands and features available to one are available to the other. Obviously Applets, since they are running on someone's computer anywhere in the world must have some restrictions (e.g.. cannot modify files on someone's computer) Most of the standard commands and control statements in Java are quite similar to those of other languages. Assignment statements, if statements, for-next statements, Do - While statements, etc. are easy to understand and pretty similar in most languages. However , using these statements to accomplish some logical end is the first stumbling block that beginning programmers need to overcome. Understanding the various data types both primitive and non primitive is of major importance to Java programmers. Primitive types are pretty obvious and used in most languages on an everyday basis. Such types are : int long short double float char Boolean etc. Non primitive types are referred to as reference variables because they point to memory locations that contain the values. Strings etc. In addition to the above another important learning step is how to organize our program so that it will work. Concepts such as top-down, or styles that use a modular approach are quite popular. Modular means to divide the logic into sections of code and then call each section as it is needed. Think of modules are being small programs. These small programs can also be called function or even METHODS. Remember that when you use them , their purpose is to perform some task. Understanding the concept of Methods is critical to appreciating the power of Java. In addition to Methods performing tasks (just like a program, they can receive values (to play with) and return results (if needed). So in short programs are groups of Methods and variables interacting. In Java we will refer to this grouping as CLASSES. So instead of writing programs we are really writing CLASSES. And each of our Classes contains METHODS (or member function) to perform specific tasks. Now the real power explained. People have written many CLASSES already. These CLASSES perform a wide range of tasks for you , so you in essence do not have to reinvent the wheel every time you need something. These CLASSES are bundled together into PACKAGES , which you import into your program (at the top). Common packages are java.awt or java.lang or java.applet etc. New CLASSES are being developed all the time. Bundled into packages and made available to the programmer. (java.swing is an example from our textbook). So in short you are not writing programs, you are writing classes that can use existing classes to help them achieve their goals When your class needs something that another class has to offer you can normally do one of two things after the import of the package containing the class: 1.. directly refer to a member function in that class to perform the task String name = JOptionPane.showInputDialog("enter your name " ) 2.. create an OBJECT of that class and then refer to the object along with the member function so the task can be performed Button red = new Button(); .... red.setBounds (1,2,44,23); In summary the full power of java and object oriented programming is realized when our class creates objects of existing classes which were created from other classes. Classes can inherit the capabilities and power of the classes from which they were derived and so on and so on. So not only are we not reinventing the wheel , we are pulling a wheel of the shelf that is already fine tuned and using that to go forward to design yet even better classes to solve problems. When designing our own classes there are way to allow access to certain methods and variables and not allow access to others. In other words we allow enough access to realize its power but not enough to mess it up. I will spend more time on these and other concepts later.