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  • How does this code break the Law of Demeter?

    - by Dave Jarvis
    The following code breaks the Law of Demeter: public class Student extends Person { private Grades grades; public Student() { } /** Must never return null; throw an appropriately named exception, instead. */ private synchronized Grades getGrades() throws GradesException { if( this.grades == null ) { this.grades = createGrades(); } return this.grades; } /** Create a new instance of grades for this student. */ protected Grades createGrades() throws GradesException { // Reads the grades from the database, if needed. // return new Grades(); } /** Answers if this student was graded by a teacher with the given name. */ public boolean isTeacher( int year, String name ) throws GradesException, TeacherException { // The method only knows about Teacher instances. // return getTeacher( year ).nameEquals( name ); } private Grades getGradesForYear( int year ) throws GradesException { // The method only knows about Grades instances. // return getGrades().getForYear( year ); } private Teacher getTeacher( int year ) throws GradesException, TeacherException { // This method knows about Grades and Teacher instances. A mistake? // return getGradesForYear( year ).getTeacher(); } } public class Teacher extends Person { public Teacher() { } /** * This method will take into consideration first name, * last name, middle initial, case sensitivity, and * eventually it could answer true to wild cards and * regular expressions. */ public boolean nameEquals( String name ) { return getName().equalsIgnoreCase( name ); } /** Never returns null. */ private synchronized String getName() { if( this.name == null ) { this.name == ""; } return this.name; } } Questions How is the LoD broken? Where is the code breaking the LoD? How should the code be written to uphold the LoD?

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  • method names with fluent interface

    - by deamon
    I have a Permissions class with methods in fluent style like this: somePermissions.setRead(true).setWrite(false).setExecute(true) The question is, whether I should name these methods set{Property} or only {property}. The latter would look like this: somePermissions.read(true).write(false).execute(true) If I look at these methods separately I would expect that read reads something, but on the other hand it is closer to the intention to have something like named paramaters like in Scala: Permission(read=true, write=false, execute=true)

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  • JAXB, marshalling sub-class that has the same rootNode name as the superclass

    - by SCdF
    Let's say I have this: public class Foo { private String value; // <snip> getters and setters, constructors etc } And I also have this: public class Bar extends Foo { private String anotherValue; // <snip> getters and setters, constructors etc } I want to be able to marshall this to a Bar object: <foo> <value>smang</value> <anotherValue>wratz</anotherValue> </foo> I'm not in a position to check right now, but if I change the @XmlRootNode name of Bar to 'foo' will that work? Do I have to do anything more clever than that?

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  • Populate a jTable Using MySQL

    - by Nathan Campos
    I have a project with a jTable called AchTable, that is like this: +-------+------+ | File | Type | +-------+------+ | | | | | | | | | +--------------+ And I have a mySQL table that is like the same, then I want to know how could I populate the jTable.

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  • Are JSF 2.x ViewScoped Beans Thread Safe?

    - by Mark
    I've been googling for a couple hours on this issue to no eval. WELD docs and the CDI spec are pretty clear regarding thread safety of the scopes provided. For example: Application Scope - not safe Session Scope - not safe Request Scope - safe, always bound to a single thread Conversation Scope - safe (due to the WELD proxy serializing access from multiple request threads) I can't find anything on the View Scope defined by JSF 2.x. It is in roughly the same bucket as the Conversation Scope in that it is very possible for multiple requests to hit the scope concurrently despite it being bound to a single view / user. What I don't know is if the JSF implementation serializes access to the bean from multiple requests. Anyone have knowledge of the spec or of the Morraja/MyFaces implementations that could clear this up?

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  • Finding the order of method calls in Eclipse

    - by Chathuranga Chandrasekara
    Suppose I have a big program that consists of hundreds of methods in it. And according to the nature of input the program flow is getting changed. Think I want to make a change to the original flow. And it is big hassle to find call hierarchy/ references and understand the flow. Do I have any solution for this within Eclipse? Or a plugin? As an example, I just need a Log of method names that is in order of time. Then I don't need to worry about the methods that are not relevant with my "given input" Update : Using debug mode in eclipse or adding print messages are not feasible. The program is sooooo big. :)

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  • Using JUnit as an acceptance test framework

    - by Chris Knight
    OK, so I work for a company who has openly adopted agile practices for development in recent years. Our unit tests and code quality are improving. One area we still are working on is to find what works best for us in the automated acceptance test arena. We want to take our well formed user stories and use these to drive the code in a test driven manner. This will also give us acceptance level tests for each user story which we can then automate. To date, we've tried Fit, Fitnesse and Selenium. Each have their advantages, but we've also had real issues with them as well. With Fit and Fitnesse, we can't help but feel they overcomplicate things and we've had many technical issues using them. The business haven't fully bought in these tools and aren't particularly keen on maintaining the scripts all the time (and aren't big fans of the table style). Selenium is really good, but slow and relies on real time data and resources. One approach we are now considering is the use of the JUnit framework to provide similiar functionality. Rather than testing just a small unit of work using JUnit, why not use it to write a test (using the JUnit framework) to cover an acceptance level swath of the application? I.e. take a new story ("As a user I would like to see basic details of my policy...") and write a test in JUnit which starts executing application code at the point of entry for the policy details link but covers all code and logic down to the stubbed data access layer and back to the point of forwarding to the next page in the application, asserting on what data the user should see on that page. This seems to me to have the following advantages: Simplicity (no additional frameworks required) Zero effort to integrate with our Continuous Integration build server (since it already handles our JUnit tests) Full skillset already present in the team (its just a JUnit test after all) And the downsides being: Less customer involvement (though they are heavily involved in writing the user stories in the first place from which the acceptance tests will be written) Perhaps more difficult to understand (or make understood) the user story and acceptance criteria in a JUnit class verses a freetext specification ala Fit or Fitnesse So, my question is really, have you ever tried this method? Ever considered it? What are your thoughts? What do you like and dislike about this approach? Finally, please only mention alternative frameworks if you can say why you like or dislike them more than this approach.

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  • What's in an Eclipse .classpath/.project file?

    - by totalEclipse
    We recently had an issue with an Eclipse project for one of our team members. Tomcat was not deploying JARs of the application. We eventually noticed the .classpath Eclipse file was not the same as for the team members where the project was OK. We replaced the .classpath file with one from a project that was OK and the Tomcat deploy was complete. Just out of curiosity and to know at what to look in the future if something is wrong, what is inside the .classpath and .project files. What can I add in there, what does it all mean?

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  • Copy object into another

    - by EugeneP
    Is there an easy way how to achieve this: MyObj : (id, name); MyObj myObj_1 = new MyObj(1, "Name 1"); MyObj myObj_2 = new MyObj(2, "Name 2"); instead of myObj_2.setName(myObj_1.getName()) etc do something as following: myObj_2.copyFrom(myObj_1) so that they are different instances, but have equal properties.

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  • Throwing exception vs returning null value with switch statement

    - by Greg
    So I have function that formats a date to coerce to given enum DateType{CURRENT, START, END} what would be the best way to handling return value with cases that use switch statement public static String format(Date date, DateType datetype) { ..validation checks switch(datetype){ case CURRENT:{ return getFormattedDate(date, "yyyy-MM-dd hh:mm:ss"); } ... default:throw new ("Something strange happend"); } } OR throw excpetion at the end public static String format(Date date, DateType datetype) { ..validation checks switch(datetype){ case CURRENT:{ return getFormattedDate(date, "yyyy-MM-dd hh:mm:ss"); } ... } //It will never reach here, just to make compiler happy throw new IllegalArgumentException("Something strange happend"); } OR return null public static String format(Date date, DateType datetype) { ..validation checks switch(datetype){ case CURRENT:{ return getFormattedDate(date, "yyyy-MM-dd hh:mm:ss"); } ... } return null; } What would be the best practice here ? Also all the enum values will be handled in the case statement

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  • How do I recieve byteArray sent from a Server and read 4 single bytes at a time.

    - by k80sg
    I need to receive 320 bytes of data from a server which consist of 80 4 byte int fields. How do I receive them in bytes of 4 and display their respective int values? Thanks. Not sure if this is right for the receiving part: //for reading the data from the socket BufferedInputStream bufferinput=new BufferedInputStream(NewSocket.getInputStream()); DataInputStream datainput=new DataInputStream(bufferinput); byte[] handsize=new byte[32]; // The control will halt at the below statement till all the 32 bytes are not read from the socket. datainput.readFully(handsize);

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  • How to make enemies?

    - by Meko
    Hi..I made shoot em up like game.But I have only one ememy which fallows me on screen.But I want to make lots of enemys like each 10 second they will across on screen together 5 or 10 enemys. ArrayList<Enemies> enemy = new ArrayList<Enemies>(); for (Enemies e : enemy) { e.draw(g); } is it good creating array list and then showing on screen? And Do I have to make some planing movements thoose enemies in my code ? I want that they vill appear not on same pozition.Like First 5 enemies will come top of screen then the other 5 or 10 enemies will come from left side.. so on.What is best solution for this?

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  • Is using the Class instance as a Map key a best practice?

    - by Pangea
    I have read somewhere that using the class instances as below is not a good idea as they might cause memory leaks. Can someone tell me if if that is a valid statement? Or are they any problems using it this way? Map<Class<?>,String> classToInstance=new HashMap(); classToInstanceMap.put(String.class,"Test obj");

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  • How to make a try-catch block that iterates through all objects of a list and keeps on calling a met

    - by aperson
    Basically iterating through a list and, - Invoke method on first object - Catch first exception (if any); if there are no more exceptions to catch, return normally. Otherwise, keep on invoking method until all exceptions are caught. - Move on to next object. I can iterate through each object, invoke the method, and catch one exception but I do not know how to continuously invoke the method on it and keep on catching exceptions :S Thanks :)

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  • Swing: Scroll to bottom of JScrollPane, conditional on current viewport location

    - by I82Much
    Hi all, I am attempting to mimic the functionality of Adium and most other chat clients I've seen, wherein the scrollbars advance to the bottom when new messages come in, but only if you're already there. In other words, if you've scrolled a few lines up and are reading, when a new message comes in it won't jump your position to the bottom of the screen; that would be annoying. But if you're scrolled to the bottom, the program rightly assumes that you want to see the most recent messages at all times, and so auto-scrolls accordingly. I have had a bear of a time trying to mimic this; the platform seems to fight this behavior at all costs. The best I can do is as follows: In constructor: JTextArea chatArea = new JTextArea(); JScrollPane chatAreaScrollPane = new JScrollPane(chatArea); // We will manually handle advancing chat window DefaultCaret caret = (DefaultCaret) chatArea.getCaret(); caret.setUpdatePolicy(DefaultCaret.NEVER_UPDATE); In method that handles new text coming in: boolean atBottom = isViewAtBottom(); // Append the text using styles etc to the chatArea if (atBottom) { scrollViewportToBottom(); } public boolean isAtBottom() { // Is the last line of text the last line of text visible? Adjustable sb = chatAreaScrollPane.getVerticalScrollBar(); int val = sb.getValue(); int lowest = val + sb.getVisibleAmount(); int maxVal = sb.getMaximum(); boolean atBottom = maxVal == lowest; return atBottom; } private void scrollToBottom() { chatArea.setCaretPosition(chatArea.getDocument().getLength()); } Now, this works, but it's janky and not ideal for two reasons. By setting the caret position, whatever selection the user may have in the chat area is erased. I can imagine this would be very irritating if he's attempting to copy/paste. Since the advancement of the scroll pane occurs after the text is inserted, there is a split second where the scrollbar is in the wrong position, and then it visually jumps towards the end. This is not ideal. Before you ask, yes I've read this blog post on Text Area Scrolling, but the default scroll to bottom behavior is not what I want. Other related (but to my mind, not completely helpful in this regard) questions: Setting scroll bar on a jscrollpane Making a JScrollPane automatically scroll all the way down. Any help in this regard would be very much appreciated.

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  • Why a "private static" is not seen in a method?

    - by Roman
    I have a class with the following declaration of the fields: public class Game { private static String outputFileName; .... } I set the value of the outputFileName in the main method of the class. I also have a write method in the class which use the outputFileName. I always call write after main sets value for outputFileName. But write still does not see the value of the outputFileName. It say that it's equal to null. Could anybody, pleas, tell me what I am doing wrong? ADDED As it is requested I post more code: In the main: String outputFileName = userName + "_" + year + "_" + month + "_" + day + "_" + hour + "_" + minute + "_" + second + "_" + millis + ".txt"; f=new File(outputFileName); if(!f.exists()){ try { f.createNewFile(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } System.out.println("IN THE MAIN!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!"); System.out.println("------>" + outputFileName + "<------"); This line outputs me the name of the file. Than in the write I have: public static void write(String output) { // Open a file for appending. System.out.println("==========>" + outputFileName + "<============"); ...... } And it outputs null.

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  • Can addition of an ActionListener be short? Can I add arguments to the actionPerformed?

    - by Roman
    I have a big table containing a button in each cell. These buttons are very similar and do almost the same. If I add an action listener to every button in this way: tmp.addActionListener(new ActionListener(){ @Override public void actionPerformed(ActionEvent evt) { proposition = proposition + action; SwingUtilities.invokeLater(new Runnable() { public void run() { updatePropositionPanel(); } }); } }); Actually, every action listener differ from all others by the value of the action. proposition and updatePropositionPanel are a field and a method of the class. First i thought that I can make it shorter if I do not use inner classes. So, I decided to program a new ActionListener class. But than I realized that in this case "proposition" will not be visible to the instances of this class. Then I decided to add the actionPerformed method to the current class and do that: addActionListener(this). But than I realized that I do not know how give arguments to the actionPerformed method. So, how does it work. Can I add an action listener in a short and elegent way?

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