What is the program java

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An application is a stand-alone program that executes independently of a browser. It is usually launched from the command line, using the command line interpreter, java.

An applet is a program that can be embedded in an HTML page. The JDK includes a tool, called appletviewer , that can also be used to view applets. We make our program an application by writing a class, HelloWorldApp , that contains a function named main. We can compile our program by typing. The command line interpreter looks for a function named main in the HelloWorldApp class and then executes it.

In this example we deliberately gave the source file a different name, but in practice, we will place each class in a separate file with the same name. This convention becomes important when we want to write a class that is publicly accessible. This is why we placed our main function inside our class. We must make our main function static , since it should not be associated with a particular object, and we must also make it public , since it is the entry point to our program.

The extends keyword declares that class HelloWorld inherits class JApplet. Before we can refer to the JApplet class, we must declare its existence using the import keyword.

Here we have imported the JApplet class, which belongs to the javax. The JApplet class possesses a method named paint , which it inherits from one of its superclasses. Our HelloWorld class inherits this paint method when it inherits the JApplet class.

The purpose of paint is to draw the contents of the applet. Unfortunately, the default paint method that we inherit cannot do anything useful since it has no way of knowing what we want to draw.

We must therefore override the default paint in our HelloWorld class. Compiler Design. Computer Organization. Discrete Mathematics.

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