The internal scripts that write text on the screen, or write HTML, it is preferable to insert them in the <body> section.
Unlike other languages, Java keeps the promise of compatibility between different platforms (cross platform), which means that a programmer could write a Java program that runs on any kind of computer, whether you run this Windows, Mac OS X or any of the different versions of Unix. In practice, Java has not completed that dream, due in large part to disputes between Sun and Microsoft regarding language direction.
First of all, Microsoft got involved because it wanted to integrate Java into Windows in its own way (a way that Sun says would make Java work in a way in Windows and otherwise in other computers, thus failing to fulfill Java's main purpose). ); later, Microsoft introduced Java for Windows, once it created its own Java-style language, C#.
After a lot of litigation between the two companies (and a big deal in favor of Sun), Microsoft eliminated its Windows Java and, now, the user can install the latest Java version of Sun for Windows (or Linux) from their official page. Mac OS X has Java installed as part of the operating system.
In addition to the independent applications, the main use of Java is on the client side, that is, on the user's browser, is the creation of applets, small programs that are downloaded on the Internet and run on Web browsers. Due to the cross-platform nature of Java, these applets should also run on any browser that supports Java. In recent years, many Java applets have been replaced by Macromedia Flash animations, which are usually easier to create than Java applets.
Today, Flash is slowly being replaced by the new possibilities offered by HTML5 along with CSS3 and jQuery. The applets are embedded in the Web pages using the HTML <object> tag, with additional information specified by the Java applet of the server and executed in the screen area specified in the tag.
There is a distinction that must be recognized: the programs that run on the user's computer are known as client-side programs; the programs that run on the server are known as server-side programs.