What’s Java?

♦1. Once upon a time

Ever since Nikki was little, he dreamed of having his own mobile phone. His dream finally came true when he started middle school, and now he uses his phone every day.
He calls friends, sends messages, and browses the Web. Besides this, he downloads games, which he enjoys playing on the handset.

One day, a friend told Nikki something interesting. Not only can you download applications made by developers, you can also create your own with something called Java for use on your handset. Nikki's curiosity was aroused, and he couldn't wait to try it himself. He dashed off to visit Professor Zhavah, a neighbor of his and expert in mobile apps, to learn how to develop his own.

♦2. What's programming all about?

	So, Nikki, you want to know how to develop your own mobile applications, eh?
	That's right. Professor Zhavah, can you help me?
	Sure!
	I can't wait to learn how to make mobile apps. My friend said that you use Java, but what's that?
	Well let's see. . . . Before I tell you about Java, I think I have to explain programming languages.
	Programming languages?
	Look, Nikki, we need to use words to talk to people, right? It's the same idea. We need words to communicate with computers, too. Those words for computer communication are programming languages. So computers read programs written in programming languages and follow the instructions to do the processing. When you use these words to write programs, you're programming.。

	Nikki, you've played computer games, haven't you?
	Yeah. I play a lot.
	Well all the games and word processing and spreadsheet programs on your computer are written in programming languages. And that's not all. The software in game consoles and mobile phones is also written in programming languages.
	Really?
	That's right. So once you know programming, you can develop all kinds of software yourself!

♦3. What's Java?

	Now that you know about programming languages, let's move on to Java.
	Cool! Please tell me about it. 。
	Java is a programming language introduced back in 1995 by Sun Microsystems. They originally developed Java for electronics applications. Java's popularity took off because it was adapted for the Internet, though, which more and more people were getting into then. And I can tell you a good reason why. Just add Java to a webpage and presto—you've got animation, games, and more. So suddenly, everyone was interested in Java. Now Java programs are used in all kinds of mobile phones, electronics and appliances, computers, and servers.

Figure 1 Java is used in many devices

	So now Java is everywhere. I'm surprised it's in electronics, appliances, and servers besides mobile phones and computers.
	That's right, my boy. One thing that makes Java so popular is that it's a cross-platform language.
	Cross-platform?
	Yes. You know about operating systems?
	Yeah. You mean like Windows and Mac OS?
	Exactly. Back in the old days, we had to rewrite programs to make them compatible with all the operating systems. Let's say you wrote a puzzle game for Windows. After you finished programming, you had to start all over again to get it to run on a Mac.
	No way! Rewrite it from the start? Why?
	Each OS is made up a different way, you know. So for the same processing, we had to account for these differences and write programs that are slightly different. That meant rewriting them.
	Oh, I get it.
	Java gets around this problem by using something called a Java Virtual Machine (JVM). Without rewriting Java programs, you can run them on different operating systems. This way, no matter what OS (or "platform") it is, the programs run the same way. They're called cross-platform programs. Remember how I said Java became popular because of the Internet? Webpages can be viewed by people using all kinds of computers, all around the world. Java became popular because Java programs run the same way regardless of the computer OS.
	Cross-platform stuff is handy!

	And I have more good news. You can get what you need for a development environment to write Java programs for free.
	No way! For free? ？
	That's right, my boy. Sun Microsystems, the grandfather of Java technology, offers these tools for free. Anyone can get the development environment for free, so anyone can create their own apps.
	Professor, how can I get the development environment? I can't wait to make my apps!
	OK, OK. All in good time, my boy. I'll tell you more about the development environment next time. First you need to understand Java better, Nikki.