TweetFollow Us on Twitter

Java Break
Volume Number:12
Issue Number:5
Column Tag:Getting Started

Java Break

By Dave Mark

Note: Source code files accompanying article are located on MacTech CD-ROM or source code disks.

Over the next few months, we’re going to take a break from PowerPlant and play around with the Java programming language. Why spend time on Java? Java is extremely popular. Java is a cool language. Many people think Java is a better language than both C and C++. Java offers an elegant mechanism for developing software that will run on a Mac, Windows machine, or a Unix box, all without recompiling.

If you are even a little interested in the World Wide Web, you should definitely learn Java. While you’ll use HTML (or an HTML-generating program) to create your web content, you can greatly enhance your Web pages by calling up Java applets from within your HTML.

Java Is Not C++

You will frequently see Java compared to C++. Though Java is very similar to C++, there are many major differences. For starters, Java doesn’t support pointers, is designed to support multi-threading, and does its own garbage collection and dynamic memory management. To add a user interface to a C++ program, you’ll take advantage of a Toolbox designed for a specific platform (in our case, we use the Mac Toolbox). To add an interface to a Java applet, you’ll take advantage of a Java-specific, platform-independent interface library called the AWT (advanced windowing toolkit) that ships with your development environment.

Java is, however, very similar to C++. As we go through our Java examples, you’ll find very few clues that this isn’t straight C++ code. Of course, I’ll do my best to point out the differences.

Before you read on, you might want to take some time to get a bit of background on the Java language. The March issue of MacTech Magazine had an excellent article by Richard Cardona called Writing Java 102 that is definitely worth a read. Of course, there have been a number of other Java articles, and there is also a steadily increasing deluge of Java books hitting the market. Check ’em out, pick one you like, dig in and learn the basics.

Getting Java on Your Machine

Before you can work with Java, you’ll need to get hold of a Java development environment. There are several choices. For starters, you can visit Sun’s Java web site (http://java.sun.com) and download the Macintosh version of the Java Development Kit (JDK). The JDK is free (except, of course, for any internet access fees) and fairly straightforward to use. It consists of all the files you need to do Java development, along with a Java compiler and an applet runner called Applet Viewer. The real problem with the JDK is that it is not a development environment, but rather a collection of tools. To compile a file, you either drop the file onto the compiler or, from inside the compiler, you select Open... from the File menu and select the file you want to compile. To edit your source code, you use SimpleText, BBEdit, or some other plain text editor. To run the compiled .class file, you go back to the Finder and drag the .class file onto the Applet Viewer. All this back-and-forth between tools and the Finder is a real pain. On the other hand, I don’t think Sun really intended the JDK to be the programmer’s choice for Java development.

Another choice for Java development is Roaster, which was released in January by Natural Intelligence. Roaster uses an integrated development environment (like CodeWarrior and SC++), allowing you to edit, compile, and run your applets from within the environment. The January release of Roaster sold for $299.

By the time you read this, Metrowerks will have shipped Discover Java, their professional Java development environment. Discover Java sells for $99, and comes with an electronic copy of Learn Java on the Macintosh by Barry Boone (Addison-Wesley, 1996). The Java development tools also ship on CodeWarrior Gold 9, so if you already subscribe to CW Gold, about all you’ll be missing is the book. Since I’m writing this about three months before Discover Java and CW9 hit the streets, check with Metrowerks (http://www.metrowerks.com, or call (800) 377-5416 or send email to sales@metrowerks.com) to get the latest on pricing and availability.

Finally, Symantec has announced Java support for the Macintosh via a product called Café. According to a press release on their Web site, Café will ship on the SC++ CD and was scheduled to ship in the first quarter of 1996.

Your First Application: Hello

Before we dig in to our first example, a quick word about terminology. Strictly speaking, the term applet applies to a Java class that is derived from the class java.applet.Applet and launched from an HTML page via the <applet> tag. Since none of our first few examples fit this definition, they are not really applets. On the other hand, these little examples aren’t really applications in the true sense of the word, since that implies that they run independent of our Java environment. However, since the term “applet” is so specific, we’ll stick with the term “application” until next month when we build our first true applet.

Our first Java application will display the obligatory “Hello, world!” message:

public class hello
{
 public static void main(String argv[])
 {
 System.out.println("Hello, world!");
 }
}

Create a new file, type in this code, then save the file as hello.java. Just as you’d end your C source code file with the extension .c and your C++ source code file with .cp or .cpp, the extension .java is used to denote a Java source code file.

If you are using the JDK, drag the file hello.java onto the application named Java Compiler (gee, guess what this is). The compiler will convert your source code into Java byte code, intended for a Java interpreter that will turn these byte codes into the instructions specific to the machine it is running on. The interpreter is part of the virtual machine, the layer that lies between the platform-independent Java byte code and your machine.

The compiler writes the Java byte code into a file named xxx.class, where xxx is the name of the class you’ve implemented. In this case, the compiler will create a file called hello.class. Again, if you are using the JDK, drag the file hello.class onto the application named Applet Viewer. As you might expect, the Applet Viewer will start running at the public method named main().

The output of this application is shown in Figure 1. Notice that the window is named stdout. If you’ve ever spent any time in the Unix universe, you know that stdout stands for “standard output”. The method System.out.println() sends its output to the stdout window followed by a carriage return. The method System.out.print() sends its output to the stdout window without generating a carriage return.

Figure 1. The output from the hello.class application

System.out.println() is a lot like printf() or cout in that they all send their output to a console window. Just as you first learned to program using consoles and eventually moved to the Mac Toolbox for your user interface, we’ll start with System.out.println() and eventually move on to the user interface routines in the AWT (advanced windowing toolkit). You’ll use the AWT to implement a user interface you’ll want to appear on a web page.

Don’t worry too much about the structure of our Java source code just yet. The three applications in this month’s column all use the same basic structure: a class wrapper with a single public method called main(). Oh yeah, in Java, a class’ functions are called methods instead of member functions.

Your Second Application: StringTester

Our second application, stringTester, introduces an important Java data type: String. As its name suggests, the String class was implemented to work with strings. Unlike C and Pascal strings, a Java String is an object, complete with variables (the Java term for data members) and methods. Our third applica-tion, stringMethods, will demonstrate some of the String methods. This application, stringTester, will get us started.

Here’s the source...

public class stringTester
{
 public static void main(String argv[])
 {
 String string1, string2 = ", world!";
 
 string1 = "Hello";
 
 System.out.print( string1 );
 System.out.println( string2 );
 System.out.println( string1 + string2 );
 
 string1 += string2;
 System.out.println( string1 );
 
 System.out.println( "Length of this string: " + 
 string1.length() );
 }
}

The first few lines show you two ways to create and initialize a String:

 String string1, string2 = ", world!";
 
 string1 = "Hello";

You can initialize the String when you define it or you can use the assignment operator, as we did in the second line. Nothing unusual here.

The next line prints the first string, “Hello”, without a carriage return. The second line prints the second string, “, world!”, with a carriage return.

 System.out.print( string1 );
 System.out.println( string2 );

This produces this line of output in the stdout window:

Hello, world!

The next line uses the + operator to concatenate string1 and string2, sending the joined string as a parameter to println().

 System.out.println( string1 + string2 );

Here’s the output produced by this code:

Hello, world!

Next, the += operator is used to concatenate string2 onto the end of string1 and the new string1 is send to stdout:

 string1 += string2;
 System.out.println( string1 );

Once again, here is the output:

Hello, world!

Finally, the length() method is called to return the length of the modified string1. Notice that the + operator is used to merge the two strings passed to println() into a single string:

 System.out.println( "Length of this string: " + 
 string1.length() );

Here’s the final line of output:

Length of this string: 13

Your Third Application: StringMethods

Our last application this month demonstrates some of the String methods. As you go through this program, take a moment to go through the documentation that came with your development environment. In particular, look for the file java.lang.String.html. As you’ll see as you learn more about Java, all the Java classes are part of some larger collection of classes. These collections take the form of packages. For example, the String class (along with the rest of the “built-in” Java types) are part of the java.lang package. To use a package, you use a mechanism similar to the #include. This mechanism is the import statement. We’ll learn about the import statement in next month’s column. The one package you automatically have access to is java.lang and so you don’t need to import it to get access to the String class.

The file java.lang.String.html contains a complete description of the variables and methods that make up the String class. Use your Web browser to open this html file and look over the class.

Here’s the stringMethods source code...

public class stringMethods
{
 public static void main(String argv[])
 {
 char myArray[] = {'a', 'b', 'c', 'd', 'e'};
 java.lang.Stringstring = new String( myArray );
 
 System.out.println( "string: " + string );
 System.out.println( "string[2]: "
 + string.charAt( 2 ) );
 
 string = string.concat( string );
 System.out.println( "Doubled string: "
 + string );
 
 System.out.println( "Index of first 'x': "
 + string.indexOf( 'x' ) );
 
 int  index = string.indexOf( 'e' );
 System.out.println( "Index of first 'e': "
 + index );
 
 if ( index >= 0 )
 System.out.println( "Index of second 'e': "
 + string.indexOf( 'e', index+1 ) );
 
 System.out.println( "substring[2] to the end: "
 + string.substring( 2 ) );
 System.out.println( "substring[2] up to string[4]: "
 + string.substring( 2, 4 ) );
 
 string = string.replace( 'c', 'x' );
 System.out.println( "Replace 'c' with 'x': "
 + string );
 
 System.out.println( "Display as upper case: "
 + string.toUpperCase() );
 }
}

The first two lines show you yet another way to create a new String. As you’ll see when you read through java.lang.String.html, there are several versions of the String constructor. Just like C++, Java supports function overloading, allowing you to create multiple versions of the same function, as long as each version has a unique signature (the function name combined with the parameter list).

This line defines an array of chars and initializes the array with the characters a through e:

 char myArray[] = {'a', 'b', 'c', 'd', 'e'};

This line uses new to define the new String object, using the char array to initialize the String to the string “abcde”. Notice that we refer to java.lang.String instead of just String. The two terms are equivalent. Since the java.lang package is automatically included, the java.lang prefix is not needed.

 java.lang.Stringstring = new String( myArray );

The next line prints this string. System is actually java.lang.System. java.lang.System features a variable called out which features methods called print() and println(). We could have referred to java.lang.System.out.println() but, again, the java.lang is assumed.

 System.out.println( "string: " + string );

Here’s the output:

string: abcde

This next println() calls the String method charAt(). charAt() returns the nth character in the String.

 System.out.println( "string[2]: "
 + string.charAt( 2 ) );
 

Here’s the output. Note that Java strings are 0-based, just like C and C++.

string[2]: c

The concat() method appends its parameter to the end of the current object. In this case, we concat() string on the end of string, storing the result in string, then print the newly doubled string.

 string = string.concat( string );
 System.out.println( "Doubled string: "
 + string );

Here’s the output...

Doubled string: abcdeabcde

The method indexOf() searches the string for the specified character, returning either an index into the string or the value -1.

 System.out.println( "Index of first 'x': "
 + string.indexOf( 'x' ) );

Here’s the output. Since the string doesn’t contain an ‘x’, indexOf() returned -1.

Index of first 'x': -1

The next lines of code searches for the first ‘e’ in the String, storing the index in the variable index, then printing the index.

 int  index = string.indexOf( 'e' );
 System.out.println( "Index of first 'e': "
 + index );

Here’s the output:

Index of first 'e': 4

Next, assuming the index was not negative, we use a second version of indexOf() which takes a second parameter. This second parameter tells indexOf() where to start its search in the string, allowing us to search the string for a second ‘e’.

 if ( index >= 0 )
 System.out.println( "Index of second 'e': "
 + string.indexOf( 'e', index+1 ) );

Here’s the output:

Index of second 'e': 9

Next, the substring() method is called. substring() takes an index into the string and returns a string that runs from the index to the end of the string.

 System.out.println( "substring[2] to the end: "
 + string.substring( 2 ) );

Here’s the output:

substring[2] to the end: cdeabcde

Next, we call a second version of substring(). This one takes a second parameter, an index that marks the end of the substring.

 System.out.println( "substring[2] up to string[4]: "
 + string.substring( 2, 4 ) );

Here’s the output:

substring[2] up to string[4]: cd

replace() replaces all occurrences of char 1 with char 2 in the string, then prints the result.

 string = string.replace( 'c', 'x' );
 System.out.println( "Replace 'c' with 'x': "
 + string );

Here’s the result:

Replace 'c' with 'x': abxdeabxde

toUpperCase() replaces all lower case letters in the string with their upper case equivalents.

 System.out.println( "Display as upper case: "
 + string.toUpperCase() );

Here’s the result:

Display as upper case: ABXDEABXDE

Till Next Month...

Next month, we’ll create our first true applet and learn a bit about the advanced windowing toolkit (AWT). Till then, take some time to read through some of the .html files that came with your development environment.

 
AAPL
$119.00
Apple Inc.
+1.40
MSFT
$47.75
Microsoft Corpora
+0.28
GOOG
$540.37
Google Inc.
-0.71

MacTech Search:
Community Search:

Software Updates via MacUpdate

Skype 7.2.0.412 - Voice-over-internet ph...
Skype allows you to talk to friends, family and co-workers across the Internet without the inconvenience of long distance telephone charges. Using peer-to-peer data transmission technology, Skype... Read more
HoudahSpot 3.9.6 - Advanced file search...
HoudahSpot is a powerful file search tool built upon MacOS X Spotlight. Spotlight unleashed Create detailed queries to locate the exact file you need Narrow down searches. Zero in on files Save... Read more
RapidWeaver 6.0.3 - Create template-base...
RapidWeaver is a next-generation Web design application to help you easily create professional-looking Web sites in minutes. No knowledge of complex code is required, RapidWeaver will take care of... Read more
iPhoto Library Manager 4.1.10 - Manage m...
iPhoto Library Manager lets you organize your photos into multiple iPhoto libraries. Separate your high school and college photos from your latest summer vacation pictures. Or keep some photo... Read more
iExplorer 3.5.1.9 - View and transfer al...
iExplorer is an iPhone browser for Mac lets you view the files on your iOS device. By using a drag and drop interface, you can quickly copy files and folders between your Mac and your iPhone or... Read more
MacUpdate Desktop 6.0.3 - Discover and i...
MacUpdate Desktop 6 brings seamless 1-click installs and version updates to your Mac. With a free MacUpdate account and MacUpdate Desktop 6, Mac users can now install almost any Mac app on macupdate.... Read more
SteerMouse 4.2.2 - Powerful third-party...
SteerMouse is an advanced driver for USB and Bluetooth mice. It also supports Apple Mighty Mouse very well. SteerMouse can assign various functions to buttons that Apple's software does not allow,... Read more
iMazing 1.1 - Complete iOS device manage...
iMazing (was DiskAid) is the ultimate iOS device manager with capabilities far beyond what iTunes offers. With iMazing and your iOS device (iPhone, iPad, or iPod), you can: Copy music to and from... Read more
PopChar X 7.0 - Floating window shows av...
PopChar X helps you get the most out of your font collection. With its crystal-clear interface, PopChar X provides a frustration-free way to access any font's special characters. Expanded... Read more
OneNote 15.4 - Free digital notebook fro...
OneNote is your very own digital notebook. With OneNote, you can capture that flash of genius, that moment of inspiration, or that list of errands that's too important to forget. Whether you're at... Read more

Latest Forum Discussions

See All

Raby (Games)
Raby 1.0.3 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0.3 (iTunes) Description: ***WARNING - Raby runs on: iPhone 5, iPhone 5C, iPhone 5S, iPhone 6, iPhone 6 Plus, iPad Mini Retina, iPad Mini 3, iPad 4, iPad Air,... | Read more »
Oddworld: Stranger's Wrath (Games)
Oddworld: Stranger's Wrath 1.0 Device: iOS Universal Category: Games Price: $5.99, Version: 1.0 (iTunes) Description: ** PLEASE NOTE: Oddworld Stranger's Wrath requires at least an iPhone 4S, iPad 2, iPad Mini or iPod Touch 5th gen... | Read more »
Bounce On Back (Games)
Bounce On Back 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: | Read more »
Make Way for Fat Chicken, from the Maker...
Make Way for Fat Chicken, from the Makers of Scrap Squad Posted by Jessica Fisher on November 26th, 2014 [ permalink ] Relevant Games has announced they will be releasing their reverse tower defense game, | Read more »
Tripnary Review
Tripnary Review By Jennifer Allen on November 26th, 2014 Our Rating: :: TRAVEL BUCKET LISTiPhone App - Designed for the iPhone, compatible with the iPad Want to create a travel bucket list? Tripnary is a fun way to do exactly that... | Read more »
Ossian Studios’ RPG, The Shadow Sun, is...
Ossian Studios’ RPG, The Shadow Sun, is Now Available for $4.99 Posted by Jessica Fisher on November 26th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Mmmm, Tasty – Having the Angry Birds for...
The very first Angry Birds debuted on iOS back in 2009. When you sit back and tally up the number of Angry Birds games out there and the impact they’ve had on pop culture as a whole, you just need to ask yourself: “How would the birds taste... | Read more »
Rescue Quest Review
Rescue Quest Review By Jennifer Allen on November 26th, 2014 Our Rating: :: PATH BASED MATCH-3Universal App - Designed for iPhone and iPad Guide a wizard to safety by matching gems. Rescue Quest might not be an entirely original... | Read more »
You Can Play the Final Chapter of Lone W...
You Can Play the Final Chapter of Lone Wolf: Dawn Over V’taag Right Now Posted by Jessica Fisher on November 26th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Swords of Anima (Games)
Swords of Anima 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: A new tactical turn-based RPG experience. Command the Savior Rex Squad in an epic journey of courage and deception. Can you... | Read more »

Price Scanner via MacPrices.net

Black Friday: $300 off 15-inch Retina MacBook...
 B&H Photo has the new 2014 15″ Retina MacBook Pros on sale for $300 off MSRP as part of their Black Friday sale. Shipping is free, and B&H charges NY sales tax only: - 15″ 2.2GHz Retina... Read more
2014 1.4GHz Mac mini on sale for $449, save $...
 B&H Photo has the new 1.4GHz Mac mini on sale for $449.99 including free shipping plus NY tax only. Their price is $50 off MSRP, and it’s the lowest price available for this new model. Adorama... Read more
Early Black Friday pricing on 27-inch 5K iMac...
 B&H Photo continues to offer Black Friday sale prices on the 27″ 3.5GHz 5K iMac, in stock today and on sale for $2299 including free shipping plus NY sales tax only. Their price is $200 off MSRP... Read more
Early Black Friday sale prices on iPad Air 2,...
 MacMall is discounting iPad Air 2s by up to $75 off MSRP as part of their Black Friday sale. Shipping is free: - 16GB iPad Air WiFi: $459 $40 off - 64GB iPad Air WiFi: $559 $40 off - 128GB iPad Air... Read more
Early Black Friday MacBook Air sale prices, $...
 MacMall has posted early Black Friday MacBook Air sale prices. Save $101 on all models for a limited time: - 11″ 1.4GHz/128GB MacBook Air: $798 - 11″ 1.4GHz/256GB MacBook Air: $998 - 13″ 1.4GHz/... Read more
Why iPhone 6 Tablet/Laptop Cannibalization Is...
247wallst.com blogger Douglas A. McIntyre noted last week that according to research posted on the Applovin blog site the iPhone 6 is outselling the iPhone 6 Plus by a wide margin . Hardly a surprise... Read more
Worldwide Tablet Growth Expected to Slow to 7...
The global tablet market is expected to record massive deceleration in 2014 with year-over-year growth slowing to 7.2%, down from 52.5% in 2013, according to a new forecast from International Data... Read more
Touchscreen Glove Company Announces New Produ...
Surrey, United Kingdom based TouchAbility specializes in design and manufacture of a wide variety of products compatible with touchscreen devices including smartphones, tablets and computers. Their... Read more
OtterBox Alpha Glass Screen Protectors for iP...
To complement the bigger, sharper displays on the latest Apple devices, OtterBox has introduced Alpha Glass screen protectors to the iPhone 6 and iPhone 6 Plus. The fortified glass screen protectors... Read more
Early Black Friday Mac Pro sale, 6-Core 3.5GH...
 B&H Photo has the 6-Core 3.5GHz Mac Pro on sale today for $3499 including free shipping plus NY sales tax. Their price is $500 off MSRP, and it’s the lowest price available for this model from... Read more

Jobs Board

*Apple* Solutions Consultant (ASC) - Apple (...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
Senior Event Manager, *Apple* Retail Market...
…This senior level position is responsible for leading and imagining the Apple Retail Team's global event strategy. Delivering an overarching brand story; in-store, Read more
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
*Apple* Solutions Consultant (ASC) - Apple (...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
*Apple* Solutions Consultant (ASC) - Apple (...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.