Welcome!

Java IoT Authors: Stackify Blog, Yeshim Deniz, Pat Romanski, Matt Lonstine, Glenda Sims

Related Topics: Java IoT

Java IoT: Article

More on Syntax Highlighting

More on Syntax Highlighting

Last month we discussed the use of Swing's Document model to create a syntax-highlighting Document model that we could just plug into JTextPane and use. This month we'll continue with that and add complete support for comments, strings and numbers. We'll also cover how easy it is to actually use the model we've developed, and test things out as we go along.

To start things out let's try and use what we have so far. If we look at the code below we can see that plugging the Document we've created into a JTextPane component is quite easy. Defining the keywords is also very easy.

JTextPane editor = new JTextPane();
CodeDocument doc = new CodeDocument();
Vector keywords = new Vector();
keywords.addElement("abstract");
keywords.addElement("boolean");
...
doc.setKeywords(keywords);
editor.setDocument(doc);

We could have just created the CodeDocument on the fly and passed it in as an argument to the constructor of the JTextPane class, but then the keywords for the Document wouldn't have been set and we'd have had to retrieve the Document and then add them.

By running the code above and typing in some text, we get the window in Figure 1 to come up.

A word of caution: If you use this and the first word you type in is in your keywords list, you¹ll get an exception. This is a known bug on the Swing Web site (for more information look at                           .http://developer.java.sun.com/developer/bugParade/bugs/4128967.html) with no known workaround. You may also notice that when you type for a while and then move the cursor back to a previous position and start typing again, the JTextPane doesn't quite repaint itself correctly. This is also a known bug of the JTextPane (for more information see http://developer.java.sun.com/developer/ bugParade/bugs/4127974.html). This has been fixed in Swing version 1.1.

Now you can test the modifications we'll be making to the CodeDocument class.

Changing the insertString Method
Some of you may have noticed that the Document Model code we developed in the previous article worked only if you actually typed in the text manually. If we had called the insertString method and passed in a string with a length longer than one character, the syntax highlighting wouldn't have worked. To fix that we'll make a simple change, moving the code that actually did the comparing to another method, and changing the insertString method to support any size string. We'll create a method called processChar that will actually do the work of checking the kind of character we're dealing with and, in turn, call the correct method to handle that character. To make the whole thing work, we can then just loop through each of the characters in the string that's passed into the insertString method, starting at the offset position (the offs variable passed into the insertString method) and ending at the offset plus the length of the string passed in. For each character we find we can call the processChar method, and voila! We can now handle any size string. To get an idea of the code, take a look below.

public void insertString(int offs,
String str,
AttributeSet a) throws BadLocationException{
super.insertString(offs, str, normal);

int strLen = str.length();
int endpos = offs + strLen;
int strpos;
for (int i=offs;i<endpos;i++){
currentPos = i;
strpos = i - offs;
processChar(str.charAt(strpos));
}
currentPos = offs;
}

The only problem with the solution above is that when reading large chunks of text you may notice a slowdown in JTextPane's performance while it loads and parses all the text. A possible solution would be to use a thread to handle any text not immediately visible to the user, parse it in the background and then...well, that'll be the subject of a future article!

Adding String Support
Now that we can support entered text of any size, let's add highlighting support for strings. Adding string support isn't too hard now that we have the basic pieces in place. We'll add a variable that we'll use to keep track of whether we're entering a string. If this flag is turned on, any text we enter following the double quote ("") will be colored in a different foreground color. Also, if this flag is turned on, no keyword processing will occur. A carriage return will automatically shut the flag off. We'll need to keep track of the start position where the flag was first turned on. This will allow us to type in some text representing a string, hit the carriage return and type other stuff, and then put the caret back on the line where the string was and resume entering the string text ­ all the while keeping the formats correct. We'll also need a variable that represents the style attribute we want for strings.

In addition to variables we'll need some new methods. For strings we'll create a checkForString() method that will determine whether we're inside a string. If it finds that we are, the mode variable will be set appropriately (this will be explained in more detail a few paragraphs down). We'll also need a method called insertTextString() that will actually reinsert the properly formatted string.

Adding Number Support
Adding support for numbers is similar to adding support for strings. We'll add a variable to hold the style attribute for numbers, and also add two more methods: checkForNumber() and insertNumberString().

Like strings, the checkForNumber() method determines whether we're actually entering valid digits. If we are, it sets the CodeDocument's mode accordingly. Like insertTextString, insertNumberString inserts the properly formatted text as a number.

Adding Comment Support
Comments are handled in a similar manner. Two new methods are needed, checkForComment() and insertCommentString(). Like numbers and text, the checkForComments method determines if a comment block has been started (it checks for the "/*" combination to start a comment and the "*/" to end a comment block). If it has, it changes the attributes of the entered text by calling the insertCommentString() method. Again, like numbers and strings, the insertCommentString() changes the formatting attri-butes of the string accordingly, and then inserts into the document. Another private variable is needed to hold the formatting attributes for comments.

Putting It All Together
Now it's time to get down and dirty. We're finally going to look at the whole process, first in general terms and then in more detail using code examples. As we mentioned earlier, the original insertString method of the CodeDocument class was changed, and much of the logic was moved to a new method called processChar(), thus allowing us to handle not only single keystrokes, but also to programmatically insert multiple character strings. ProcessChar() works by making certain assumptions about what characters will follow other characters. Based on this, it sets the insert mode for the current position of incoming text. Based on this mode (which is simply a private integer variable), it can then determine which insertXXXString() method to call.

For example, when it encounters the character '9', it figures there's a very good chance that this is the start of a number or that a number is currently in the process of being entered. To verify this it calls the checkForNumber() method. If checkForNumber() determines that we're still entering a number, it sets the mode to the number entry mode. If it discovers any other character present, however, such as a space, a parenthesis or a letter, it sets the mode to the default text entry mode (the number entry mode is represented by the static constant NUMBER_MODE, while the text entry mode is represented by the static constant TEXT_MODE). The other checkForXXX() methods work in a similar fashion. After the checkForXXX() method has returned, the mode will have been set correctly and, based on this, the proper insertXXXString() method can be called. If the mode is in TEXT_MODE, the formatting is left alone.

Now look at the code in Listing 1 for method processChar. The first thing the method does is to check if we're in COMMENT_MODE. Because comments can include anything (aside from the comment-terminating characters), we'll let the mode default to COMMENT_MODE; otherwise we'll change it to default to TEXT_MODE, which is the standard text entry mode (no formatting). Next, a switch statement is created based on the character passed to the processChar method. As mentioned before, the method works on the assumption that the character being entered belongs to one of five groups (generic text, keywords, strings, numbers or comments), and that the case statements are grouped accordingly. Characters equaling the numbers '1' through '9' cause a check for numbers; characters equaling '*' or '/' suggest the possible start or end of a comment block, and a check is made; and so on. Once the switch statement is finished executing, a final check is made for quoted strings if we're still in TEXT_MODE. Finally, depending on which mode we're in, a call is made to the appropriate insertXXXString method.

There are four check methods: checkForComment(), checkForKeyword(), checkForNumber() and checkForString(). While there are some differences from the original checkForKeywords() method, the basic idea, as discussed last month, is the same. We retrieve the current element, get the text from it, find our position in the element and then, starting at the end, we walk backward until a delimiter of some sort is found and then set the mode accordingly. Let's look at some of the checkForString() method's code to examine this more closely. We'll assume we already have the correct offset from the Document's element.

..
..
int quoteCount = 0;
if ((offs >= 0) && (offs <= strLen-1)){
i = offs;
while (i >0){
//the while loop walks back until we hit a delimiter

char charAt = elementText.charAt(i);
if ((charAt == '"')){
quoteCount ++;
}
i--;
}
int rem = quoteCount % 2;
mode = (rem == 0) ? TEXT_MODE: STRING_MODE;
}

The code is fairly simple: we loop backward until we run out of characters to process, each time comparing a character from the element text. If the character is a double quote (" "), we add one to the local variable called quoteCount. Once we're done with the loop, we check the remainder of the quoteCount divided by two and assign the results to another local variable called rem. Why do this? Again, this is another assumption about the way words are put together. Since quotes always come in pairs, if our remainder isn't equal to zero, we know we're "inside" a string quotation. Otherwise we can safely assume that we're "outside" and are just entering normal text.

And Finally...
I think at this point I've probably run out of column space. We now have a syntax-highlighting Document class that supports any user-defined set keywords, plus string, number and comment highlighting (see Listings 2 and 3). We've also seen how easy it is to incorporate our Document class into the JTextPane control to test our results as we go along. In the next article we'll add some more user-definable properties so you can change the color of highlighted string, comments, keywords and so on. We'll also look at adding support for a kind of "smart editor" à la Borland's Code Insight features in their IDE editors.

References

  1. Topley, K. (1998). Core Java Foundation Classes. Prentice Hall PTR. Prentice-Hall Inc.
  2. Eckstein, R., Loy, R, and Wood, D. (1998) Java Swing. O'Reilly and Associates Inc.

More Stories By Jim Crafton

Jim Crafton is software developer currently doing a variety of work in C++, C#, and Java. He is the author of the Visual Component Framework (more at http://vcf-online.org/), an advanced C++ application framework. He's also interested in graphics, particularly 3D graphics using tools like Houdini and ZBrush.

Comments (0)

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


@ThingsExpo Stories
DX World EXPO, LLC, a Lighthouse Point, Florida-based startup trade show producer and the creator of "DXWorldEXPO® - Digital Transformation Conference & Expo" has announced its executive management team. The team is headed by Levent Selamoglu, who has been named CEO. "Now is the time for a truly global DX event, to bring together the leading minds from the technology world in a conversation about Digital Transformation," he said in making the announcement.
"Space Monkey by Vivent Smart Home is a product that is a distributed cloud-based edge storage network. Vivent Smart Home, our parent company, is a smart home provider that places a lot of hard drives across homes in North America," explained JT Olds, Director of Engineering, and Brandon Crowfeather, Product Manager, at Vivint Smart Home, in this SYS-CON.tv interview at @ThingsExpo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
SYS-CON Events announced today that Conference Guru has been named “Media Sponsor” of the 22nd International Cloud Expo, which will take place on June 5-7, 2018, at the Javits Center in New York, NY. A valuable conference experience generates new contacts, sales leads, potential strategic partners and potential investors; helps gather competitive intelligence and even provides inspiration for new products and services. Conference Guru works with conference organizers to pass great deals to gre...
The Internet of Things will challenge the status quo of how IT and development organizations operate. Or will it? Certainly the fog layer of IoT requires special insights about data ontology, security and transactional integrity. But the developmental challenges are the same: People, Process and Platform. In his session at @ThingsExpo, Craig Sproule, CEO of Metavine, demonstrated how to move beyond today's coding paradigm and shared the must-have mindsets for removing complexity from the develop...
In his Opening Keynote at 21st Cloud Expo, John Considine, General Manager of IBM Cloud Infrastructure, led attendees through the exciting evolution of the cloud. He looked at this major disruption from the perspective of technology, business models, and what this means for enterprises of all sizes. John Considine is General Manager of Cloud Infrastructure Services at IBM. In that role he is responsible for leading IBM’s public cloud infrastructure including strategy, development, and offering m...
"Evatronix provides design services to companies that need to integrate the IoT technology in their products but they don't necessarily have the expertise, knowledge and design team to do so," explained Adam Morawiec, VP of Business Development at Evatronix, in this SYS-CON.tv interview at @ThingsExpo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
To get the most out of their data, successful companies are not focusing on queries and data lakes, they are actively integrating analytics into their operations with a data-first application development approach. Real-time adjustments to improve revenues, reduce costs, or mitigate risk rely on applications that minimize latency on a variety of data sources. In his session at @BigDataExpo, Jack Norris, Senior Vice President, Data and Applications at MapR Technologies, reviewed best practices to ...
Widespread fragmentation is stalling the growth of the IIoT and making it difficult for partners to work together. The number of software platforms, apps, hardware and connectivity standards is creating paralysis among businesses that are afraid of being locked into a solution. EdgeX Foundry is unifying the community around a common IoT edge framework and an ecosystem of interoperable components.
Large industrial manufacturing organizations are adopting the agile principles of cloud software companies. The industrial manufacturing development process has not scaled over time. Now that design CAD teams are geographically distributed, centralizing their work is key. With large multi-gigabyte projects, outdated tools have stifled industrial team agility, time-to-market milestones, and impacted P&L stakeholders.
"Akvelon is a software development company and we also provide consultancy services to folks who are looking to scale or accelerate their engineering roadmaps," explained Jeremiah Mothersell, Marketing Manager at Akvelon, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
"IBM is really all in on blockchain. We take a look at sort of the history of blockchain ledger technologies. It started out with bitcoin, Ethereum, and IBM evaluated these particular blockchain technologies and found they were anonymous and permissionless and that many companies were looking for permissioned blockchain," stated René Bostic, Technical VP of the IBM Cloud Unit in North America, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Conventi...
In his session at 21st Cloud Expo, Carl J. Levine, Senior Technical Evangelist for NS1, will objectively discuss how DNS is used to solve Digital Transformation challenges in large SaaS applications, CDNs, AdTech platforms, and other demanding use cases. Carl J. Levine is the Senior Technical Evangelist for NS1. A veteran of the Internet Infrastructure space, he has over a decade of experience with startups, networking protocols and Internet infrastructure, combined with the unique ability to it...
22nd International Cloud Expo, taking place June 5-7, 2018, at the Javits Center in New York City, NY, and co-located with the 1st DXWorld Expo will feature technical sessions from a rock star conference faculty and the leading industry players in the world. Cloud computing is now being embraced by a majority of enterprises of all sizes. Yesterday's debate about public vs. private has transformed into the reality of hybrid cloud: a recent survey shows that 74% of enterprises have a hybrid cloud ...
"Cloud Academy is an enterprise training platform for the cloud, specifically public clouds. We offer guided learning experiences on AWS, Azure, Google Cloud and all the surrounding methodologies and technologies that you need to know and your teams need to know in order to leverage the full benefits of the cloud," explained Alex Brower, VP of Marketing at Cloud Academy, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clar...
Gemini is Yahoo’s native and search advertising platform. To ensure the quality of a complex distributed system that spans multiple products and components and across various desktop websites and mobile app and web experiences – both Yahoo owned and operated and third-party syndication (supply), with complex interaction with more than a billion users and numerous advertisers globally (demand) – it becomes imperative to automate a set of end-to-end tests 24x7 to detect bugs and regression. In th...
"MobiDev is a software development company and we do complex, custom software development for everybody from entrepreneurs to large enterprises," explained Alan Winters, U.S. Head of Business Development at MobiDev, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
Coca-Cola’s Google powered digital signage system lays the groundwork for a more valuable connection between Coke and its customers. Digital signs pair software with high-resolution displays so that a message can be changed instantly based on what the operator wants to communicate or sell. In their Day 3 Keynote at 21st Cloud Expo, Greg Chambers, Global Group Director, Digital Innovation, Coca-Cola, and Vidya Nagarajan, a Senior Product Manager at Google, discussed how from store operations and ...
"There's plenty of bandwidth out there but it's never in the right place. So what Cedexis does is uses data to work out the best pathways to get data from the origin to the person who wants to get it," explained Simon Jones, Evangelist and Head of Marketing at Cedexis, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
SYS-CON Events announced today that CrowdReviews.com has been named “Media Sponsor” of SYS-CON's 22nd International Cloud Expo, which will take place on June 5–7, 2018, at the Javits Center in New York City, NY. CrowdReviews.com is a transparent online platform for determining which products and services are the best based on the opinion of the crowd. The crowd consists of Internet users that have experienced products and services first-hand and have an interest in letting other potential buye...
SYS-CON Events announced today that Telecom Reseller has been named “Media Sponsor” of SYS-CON's 22nd International Cloud Expo, which will take place on June 5-7, 2018, at the Javits Center in New York, NY. Telecom Reseller reports on Unified Communications, UCaaS, BPaaS for enterprise and SMBs. They report extensively on both customer premises based solutions such as IP-PBX as well as cloud based and hosted platforms.