Swing library is an official Java GUI toolkit released by Sun Microsystems. The main characteristics of the There is also another GUI library for the Java programming language. It is called SWT. The King speech. JTextArea area = new. The Java Programming Language. ing programs that use interface mechanisms like buttons and menus. The prefix “javax” reveals. dercliconthepo.tk • IDE . ing UI. 1. Create a top-level application window, using a Swing container (JFrame or JDialog). 2.
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(Refer to the API documentation or Java tutorial for more information about ing. So another way to guarantee that all components will use. Up to Speed with Swing is a tutorial on how to develop applications using the Sun has been investing in the concept of Java as an operat- ing system platform. chapter begins by looking briefly at the history of the Java programming lan- guage and ing system—the user interface components are rendered by Windows or by Motif, not and the main concern of this book, is the Swing component set.
Finally, section 5 con- cludes the paper and discusses future work. Study parameters leaf node This section introduces the parameters to our study. Sub- Figure 2. JTree appearance sections 2. Subsection 2. This brings the total fields and lection process.
To ensure the quality of such a study, it is critical to fully 2. JTree design understand the relevant details about the subject frame- Figure 2 presents a sample tree picture and Figure 3 de- work. To help Javadoc API documentation, but also a few books on Swing build connection with features, we marked the diagram with such as the Swing tutorial . In particular, we compared feature numbers. At the core of this design is the observa- the identified features with the book to make sure that our tion relationship between a JTree component and its data features were both complete and consistent with the origi- model.
A tree model is made up of tree nodes that wrap nal design. Given a tree model, a JTree object draws its tree nodes using a tree cell renderer, which can be 2.
JButton design customized to produce required visual effects. To under- JTree edits its tree nodes using a tree cell editor. Documentation for know tree nodes and the current visual state of the tree. This these features can be found in . For ex- its fields and methods from the three superclasses Ta- ample, one may determine the icon for a leaf node accord- ble 1.
AbstractButton consists of 24 fields and 80 meth- ing to the current state of the tree. JTree related classes and interfaces teraction such as expanding or collapsing an internal node, and view manipulation such as setting the height of rows. Similarly to JButton, JTree inherits a total of 13 fields CellEditor is an interface for an editor that can be used to and methods Table 1 from java.
Component, edit a node interactively. Each JTree must have one Tree- java. Container, and javax. Swing pro- JTree class itself consists of 31 fields and meth- vides default implementations for both interfaces, namely, ods, and its auxiliary classes and interfaces have DefaultTreeCellRenderer and DefaultTreeCellEditor.
See Table 2 for a detailed break- The TreeModelListener interface specifies event han- down of these numbers. Using these numbers as indica- dlers for TreeModelEvent events that a tree model gen- tors of component complexity, we can see that JTree erates. The JTree class can generate two types of events fields and methods is much more complicated than JBut- for expanding or collapsing a node; and selecting a node.
Given a tree resent the two events. The data model is characterized by the TreeModel interface. The Swing Forum is one of the four most for tree data structures.
The TreeNode interface defines a popular.
From July 2, to node in the view by the sequence of nodes on the path from January 19, , there are , messages in 64, top- the root to the node. This forum is TreeCellRenderer specifies an interface for a renderer very active. An inspection did not find any single date with- object that can actually draw a node for the tree.
Tree- out postings. The number of messages in the forum was overwhelming We first filtered out domain-specific questions. For the for a manual analysis. We narrowed down the scope of mes- remaining questions, we learned many solutions from oth- sages to those containing the keywords JButton or JTree. This was especially the case at the beginning We then excluded irrelevant ones. For example, a message phase. However, not all questions had obvious answers.
We may mention JButton incidentally while describing some- then had to do some research on our own. We made sure that thing else. For JTree we also left out illegible messages. We found that A message was deemed illegible if and only if there were writing sample programs was an effective way of dealing no answers to it and despite our best effort, we still could with such problems. As we spent more time on the frame- not understand it. We did not filter out messages describ- work, our knowledge was incrementally built up.
Eventu- ing problems of the same nature unless they were dupli- ally we were able to solve new problems all on our own. This abil- ity is critical to our classification as the true problem un- 2.
Data analysis and classification derlying a question can lie deeper than what the authors de- To ensure the quality of the analysis, the first author and a scribed on the surface. We dug out the root cause and clas- colleague first independently analyzed the JTree questions.
The discrepancy between their results were then identified and resolved one by one. The analysis for JButton ques- tions was done by the first author only, partly because JBut- ton is much simpler than JTree and partly because after the 3.
Results JTree analysis, he was experienced enough to analyze JBut- ton independently. We collected and analyzed a sample of JButton Depending on the purpose of a study, one can classify questions and JTree questions.
These questions were these questions based on either the nature of the problems then classified by the design features of JButton and JTree. Problem-oriented classi- The classification results are summarized in Tables 3 and 4.
Since our goal design features and provide selected questions to illustrate was to understand the interaction issue in using the frame- the difficulties. For presentation purpose, we have corrected work interface, which is tightly related to framework de- the spelling errors in the original messages.
Full details of sign, we chose a solution-oriented approach. Had we de- the collected messages and the classification can be found cided to study the functional scope of the framework, then in . These questions were related to layout manage- Design features Sub-features Questions ment . JButton happened to be the components men- inherited features 26 revalidate and repaint 10 tioned by the authors.
These questions were about focus 3 JButton interacting with other components. For example, event handling thread some programmers added buttons directly to top-level con- component hierarchy tainers rather than their content panes; some did not know position that in order to obtain a scrolling behavior, a JTree must be keyboard put into a JScrollPane. The misc category is further divided into design layout 11 discussion, debugging, basics, platform bugs, and illegible component interaction 7 messages.
This posting was particularly interesting, fol- illegible messages 9 lowed by 16 replies. JButton questions b. JButton questions label. I have an application in which and misc Listener calls.
Addition- ponent like JButton, inherited features were responsible for ally, the component in my application which corresponds more questions than component specific features. Another to the JLabel is very large. Does anyone have any recom- finding is that the forum is a good venue to ask questions, mendations for a clean and graceful way for my component to deregister all of its anonymous listeners without hav- find bugs, and discuss design problems.
Inherited features. Here is an example of a question re- Indeed, a table keeping track of which listeners are regis- lated to inherited features. I am trying to display an image over a JButton inside a JDia- log. I am sure that it is drawn on 3. Ac- Model-view relationship. A tree consists of two kinds tually I am resizing the JDialog since I have two buttons, one to minimize and the other to maximize the size of the JDailog.
The All the buttons are in place but not visible neither at the first tree model is shared by all the views. Whenever the tree place nor when the JDialog is resized. The tree model of a JTree can be dynamically updated. Button-specific questions. Here is an example of a That is, one can add and remove a tree node; or change the button-specific question.
I can activate the button with a mouse left-click but not with a right-click. I got mouse events about these methods omitted. Programmers must choose a for both left and right clicks in mousePressed , but only the method suitable for their particular tasks.
A thorny prob- left-click activated the JButton. In the following we give two examples. Under certain con- cally. When 5 Design features Sub-features Questions insertNodeInto model-view 44 nodeChanged notification failures nodesChanged tree model sharing nodeStructureChanged node appearance 44 nodesWereInserted leaf nodesWereRemoved text and icon reload tool tips reload TreeNode node components as renderer removeNodeFromParent view manipulation 35 multi-root tree Table 5.
Does anyone have an idea what is going on here? One was that the same saving editor result JTree object was shared by two different panels. Thus it appearance broke the invariant that a component hierarchy must be a inherited features 19 tree. The other was that the programmer seemed to be un- mouse aware that a tree model can be shared by multiple trees.
The paint problem could be solved by creating two JTree objects and JScrollPane letting them share the tree model. JTree uses a tree cell renderer object user objects to draw its nodes. At the conceptual level, whenever a draw- tree listeners 10 ing is needed, the following algorithm is executed: misc 5 for each node in tree model domain problems draw node with the renderer object design discussion Several states are related to the visual aspects of tree Total nodes.
A node can have a icon, a text, and a tooltip. It can be either an internal node or a leaf. A leaf and an internal node Table 4. JTree questions require different icons. An internal node can be either ex- panded or collapsed, indicated by corresponding icons. Fi- the JTree is collapsed, it works fine. But when the JTree is nally, a node can be selected and highlighted visually. I have tried several to capture all the relevant state for the node to be drawn: methods like tree.
If selected is true, the notify the JTree that a node had been removed cell will be drawn as if selected. This could be solved expanded is true the node is currently expanded and if leaf is true the node by invoking either nodeStructureChanged or represents a leaf and if hasFocus is removeNodeFromParent. Returns the Component I got a JTree object I want to display on two different panes that the renderer uses to draw the value.
Each pane has a panel where the JTree will Returns: go. Both panels are identical and start with a simple label say- the Component that the renderer uses to ing the tree data is still building. Each pane implements Ob- draw the value server and when the tree has completed loading from a SQL database , it notifies its observers. So far so good. The renderer object knows ev- problem. On one pane, the tree shows up and works great, ie, erything about the tree and the node to be drawn.
As such, it responds to mouse clicks. Almost all adjustments to mouse clicks. Additionally, if I switch to a different pane and node appearance involve this renderer object. Up to now I selected parameter in the above method signature means have been using a string from the object, as all the examples show how to do, but I need to call functions from that ob- that the node is selected. I have found no examples that do this through the sev- icon on a node when it is selected. I could extend my own version of it, but how to setup different icons for different nodes using a ren- not sure how to get the tree to display the name strings.
Programmers seemed to under- TreeCellRenderer: stand listeners, and there were only 10 questions in this cat- if sel egory. The misc category has 5 questions. Some were about this. The JTree class itself contains a for a task that was not particularly relevant to the frame- rich set of methods to manipulate its visual aspects such work. Analysis of results and multiple-root tree. Even though most of them are stan- dalone and simple to use, a rather large number of questions The classification results drew our attention to particu- were asked in this category.
We carefully re-examined Node editor. Similarly to tree cell renderers, JTree also these features and identified a few design issues. We also uses a tree cell editor to edit nodes.
By default, the editor cross-checked these features with existing documenta- can be activated by a combination of three mouse clicks. Fi- ically.
The next discover some people issues relevant to the general frame- example is about invoking an editor. In this section, we discuss our findings in terms of three I have a JTree with editable nodes and it works fine with the triple click to start the edit or the click, pause, click.
How aspects: design, documentation, and people. Tightly coupled variation points. A variation point pro- vides programmers the ability to hook into a framework. If As the following code snippet shows, the programmer a variation point depends on too many parts of the frame- can invoke the editor by calling startEditingPath. JTree also inherits a set of features default implementations accordingly. For ex- lated to JTree.
This can be understood intuitively by ample, one asked how to determine if the mouse enters examining the dependences in Figure 3.
Note that in the fig- or leaves a node, which can be done by first registering ure, the tree cell renderer node depends on both JTree a mouse listener to the JTree and then invoking a method and TreeModel. At the programming level, this depen- from JTree to determine if the mouse is within the area of dence is reflected by the long list of parameters of the a node. Another asked how to set the background of the getTreeCellRendererComponent method.
Our tree area to some image, which can be solved by overrid- classification corroborated this observation: the node ap- ing paintComponent. Thus this Tree model.
This category involves everything about variation point is considered problematic. Here is an example of a pro- Unfortunately, the details of this variation point grammer not knowing how to wrap up a user object with a were not documented carefully enough. The one para- DefaultMutableTreeNode object. Here is an cover all its potential usage.
Upon examining the Swing tu- example. A second example is the tree cell editor, which is sim- My question is: how can I set a particular node NOT leaf as if it had children even if it is a leaf node in my JTree?
A layout manager depends on the structure of the This programmer forgot to invoke the related method GUI component hierarchy and information about the size setAskAllowsChildren on on his tree model. There- Inherited features. Table 3 shows that 26 out of fore, it is tightly coupled with the internal working of the JButton questions are related to inherited features. A careful Swing framework. This is probably because Swing provides a a large portion of questions 16 out of 26 were related to set of seven layout managers and carefully documents each the paint feature, and the revalidate and repaint feature .
These two features are at the core of the framework and dif- De-localized concerns. An object-oriented design such ficult to understand for most programmers. The difference between JButton be scattered in multiple syntactic constructs. Refer to the diagrammatic representation for better understanding: In the above image, two Strings are created using literal i. Before we go ahead, One key point I would like to add that unlike other data types in Java, Strings are immutable.
By immutable, we mean that Strings are constant, their values cannot be changed after they are created.
Because String objects are immutable, they can be shared. It returns count of total number of characters present in the String.
It either returns positive number, negative number or 0. It is like appending another string. If the java String is Empty, it returns true else false. If it exists, then removes the spaces and return the omitted string. Java String ValueOf : This method converts different types of values into string. Using this method, you can convert int to string, long to string, Boolean to string, character to string, float to string, double to string, object to string and char array to string.
Java String replace : The Java String replace method returns a string, replacing all the old characters or CharSequence to new characters. There are 2 ways to replace methods in a Java String. Java String contains :The java string contains method searches the sequence of characters in the string. If the sequences of characters are found, then it returns true otherwise returns false.
If all the characters are matched, it returns true else it will return false. In this method, if the characters match, it returns true else false. Java String toCharArray : This method converts the string into a character array i. Java StringGetBytes : The Java string getBytes method returns the sequence of bytes or you can say the byte array of the string.